Definition.

Solar cycles have an average duration of about 11 years. Solar maximum and solar minimum refer to periods of maximum and minimum sunspot counts. Cycles span from one minimum to the next.

Observational history.

Sunspots were first systematically observed by Galileo Galilei, Christoph Scheiner and contemporaries from around 1609. The solar cycle was discovered in 1843 by Samuel Heinrich Schwabe, who after 17 years of observations noticed a periodic variation in the average number of sunspots. Schwabe was however preceded by Christian Horrebow who in 1775 wrote: "it appears that after the course of a certain number of years, the appearance of the Sun repeats itself with respect to the number and size of the spots" based on his observations of the sun from 1761 and onwards from the observatory Rundetaarn in Copenhagen. Rudolf Wolf compiled and studied these and other observations, reconstructing the cycle back to 1745, eventually pushing these reconstructions to the earliest observations of sunspots by Galileo and contemporaries in the early seventeenth century.  Following Wolf's numbering scheme, the 1755–1766 cycle is traditionally numbered "1". Wolf created a standard sunspot number index, the Wolf index, which continues to be used today.  The period between 1645 and 1715, a time of few sunspots, is known as the Maunder minimum, after Edward Walter Maunder, who extensively researched this peculiar event, first noted by Gustav Spörer.  In the second half of the nineteenth century Richard Carrington and Spörer independently noted the phenomena of sunspots appearing at different solar latitudes at different parts of the cycle.  The cycle's physical basis was elucidated by George Ellery Hale and collaborators, who in 1908 showed that sunspots were strongly magnetized (the first detection of magnetic fields beyond the Earth). In 1919 they showed that the magnetic polarity of sunspot pairs:  Hale's observations revealed that the complete magnetic cycle spans two solar cycles, or 22 years, before returning to its original state (including polarity). Because nearly all manifestations are insensitive to polarity, the "11-year solar cycle" remains the focus of research; however, the two halves of the 22-year cycle are typically not identical: the 11-year cycles usually alternate between higher and lower sums of Wolf's sunspot numbers (the Gnevyshev-Ohl rule).  In 1961 the father-and-son team of Harold and Horace Babcock established that the solar cycle is a spatiotemporal magnetic process unfolding over the Sun as a whole. They observed that the solar surface is magnetized outside of sunspots, that this (weaker) magnetic field is to first order a dipole, and that this dipole undergoes polarity reversals with the same period as the sunspot cycle. Horace's Babcock Model described the Sun's oscillatory magnetic field as having a quasi-steady periodicity of 22 years. It covered the oscillatory exchange of energy between toroidal and poloidal solar magnetic field ingredients.

Cycle history.

Sunspot numbers over the past 11,400 years have been reconstructed using carbon-14-based dendroclimatology. The level of solar activity beginning in the 1940s is exceptional – the last period of similar magnitude occurred around 9,000 years ago (during the warm Boreal period). The Sun was at a similarly high level of magnetic activity for only ~10% of the past 11,400 years. Almost all earlier high-activity periods were shorter than the present episode. Fossil records suggest that the Solar cycle has been stable for at least the last 700 million years. For example, the cycle length during the Early Permian is estimated to be 10.62 years and similarly in the Neoproterozoic.  Until 2009, it was thought that 28 cycles had spanned the 309 years between 1699 and 2008, giving an average length of 11.04 years, but research then showed that the longest of these (1784–1799) may actually have been two cycles. If so then the average length would be only around 10.7 years. Since observations began cycles as short as 9 years and as long as 14 years have been observed, and if the cycle of 1784–1799 is double then one of the two component cycles had to be less than 8 years in length. Significant amplitude variations also occur.  A list of historical "grand minima" of solar activity exists.

Recent cycles.

Cycle 25.

Several predictions have been made for sunspot cycle 25 based on different methods, for the forthcoming solar cycle 25, ranging from very weak to moderate magnitude. A recent physics-based prediction relying on the data-driven solar dynamo and solar surface flux transport models by Bhowmik and Nandy (2018) seems to have predicted the strength of the solar polar field at the current minima correctly and forecasts a weak but not insignificant solar cycle 25 similar or slightly stronger in strength relative to cycle 24. Notably, they rule out the possibility of the Sun falling in to a Maunder minimum like (inactive) state over the next decade. A preliminary consensus by a Solar Cycle 25 Prediction Panel was made in early 2019. The Panel, which was organized by NOAA's Space Weather Prediction Center (SWPC) and NASA, based on the published solar cycle 25 predictions, concluded that Solar Cycle 25 will be very similar to Solar Cycle 24. They anticipate that the Solar Cycle minimum before Cycle 25 will be long and deep, just as the minimum that preceded Cycle 24. They expect solar maximum to occur between 2023 and 2026 with a sunspot range of 95 to 130, given in terms of the revised sunspot number.

Cycle 24.

The current solar cycle began on 4 January 2008, with minimal activity until early 2010. The cycle featured a "double-peaked" solar maximum. The first peak reached 99 in 2011 and the second in early 2014 at 101. It appears likely that Cycle 24 will end sometime between mid-2019 and late 2020.

Cycle 23.

This cycle lasted 11.6 years, beginning in May 1996 and ending in January 2008. The maximum smoothed sunspot number (monthly number of sunspots averaged over a twelve-month period) observed during the solar cycle was 120.8 (March 2000), and the minimum was 1.7. A total of 805 days had no sunspots during this cycle.

Phenomena.

Because the solar cycle reflects magnetic activity, various magnetically driven solar phenomena follow the solar cycle, including sunspots and coronal mass ejections.

Sunspots.

The Sun's apparent surface, the photosphere, radiates more actively when there are more sunspots. Satellite monitoring of solar luminosity revealed a direct relationship between the Schwabe cycle and luminosity with a peak-to-peak amplitude of about 0.1%. Luminosity decreases by as much as 0.3% on a 10-day timescale when large groups of sunspots rotate across the Earth's view and increase by as much as 0.05% for up to 6 months due to faculae associated with large sunspot groups.  The best information today comes from SOHO (a cooperative project of the European Space Agency and NASA), such as the MDI magnetogram, where the solar "surface" magnetic field can be seen.  As each cycle begins, sunspots appear at mid-latitudes, and then move closer and closer to the equator until a solar minimum is reached. This pattern is best visualized in the form of the so-called butterfly diagram. Images of the Sun are divided into latitudinal strips, and the monthly-averaged fractional surface of sunspots is calculated. This is plotted vertically as a color-coded bar, and the process is repeated month after month to produce this time-series diagram.  While magnetic field changes are concentrated at sunspots, the entire sun undergoes analogous changes, albeit of smaller magnitude.

Coronal mass ejection.

The solar magnetic field structures the corona, giving it its characteristic shape visible at times of solar eclipses. Complex coronal magnetic field structures evolve in response to fluid motions at the solar surface, and emergence of magnetic flux produced by dynamo action in the solar interior. For reasons not yet understood in detail, sometimes these structures lose stability, leading to coronal mass ejections into interplanetary space, or flares, caused by sudden localized release of magnetic energy driving emission of ultraviolet and X-ray radiation as well as energetic particles. These eruptive phenomena can have a significant impact on Earth's upper atmosphere and space environment, and are the primary drivers of what is now called space weather.  The occurrence frequency of coronal mass ejections and flares is strongly modulated by the cycle. Flares of any given size are some 50 times more frequent at solar maximum than at minimum. Large coronal mass ejections occur on average a few times a day at solar maximum, down to one every few days at solar minimum. The size of these events themselves does not depend sensitively on the phase of the solar cycle. A case in point are the three large X-class flares that occurred in December 2006, very near solar minimum; an X9.0 flare on Dec 5 stands as one of the brightest on record.

Patterns.

The Waldmeier effect names the observation that cycles with larger maximum amplitudes tend to take less time to reach their maxima than cycles with smaller amplitudes; maximum amplitudes are negatively correlated to the lengths of earlier cycles, aiding prediction.  Solar maxima and minima also exhibit fluctuations at time scales greater than solar cycles. Increasing and decreasing trends can continue for periods of a century or more.  The Schwabe Cycle is thought to be an amplitude modulation of the 87 year (70–100 year) Gleissberg cycle, named after Wolfgang Gleißberg. The Gleissberg cycle implied that the next solar cycle have a maximum smoothed sunspot number of about 145±30 in 2010 (instead 2010 was just after the cycle's solar minimum) and that the following cycle have a maximum of about 70±30 in 2023.  Associated centennial variations in magnetic fields in the Corona and Heliosphere have been detected using Carbon-14 and beryllium-10 cosmogenic isotopes stored in terrestrial reservoirs such as ice sheets and tree rings and by using historic observations of Geomagnetic storm activity, which bridge the time gap between the end of the usable cosmogenic isotope data and the start of modern satellite data.  These variations have been successfully reproduced using models that employ magnetic flux continuity equations and observed sunspot numbers to quantify the emergence of magnetic flux from the top of the solar atmosphere and into the Heliosphere, showing that sunspot observations, geomagnetic activity and cosmogenic isotopes offer a convergent understanding of solar activity variations.

Hypothesized cycles.

Periodicity of solar activity with periods longer than the sunspot cycle of about 11 (22) years has been proposed, including:  The 210 year Suess cycle (a.k.a. "de Vries cycle", named after Hans Eduard Suess and Hessel De Vries respectively) is recorded from radiocarbon studies, although "little evidence of the Suess Cycle" appears in the 400-year sunspot record.  The Hallstatt cycle (named after a cool and wet period in Europe when glaciers advanced) is hypothesized to extend for approximately 2,400 years.  An as yet unnamed cycle may extend over 6,000 years.  In carbon-14 cycles of 105, 131, 232, 385, 504, 805 and 2,241 years have been observed, possibly matching cycles derived from other sources. Damon and Sonett proposed carbon 14-based medium- and short-term variations of periods 208 and 88 years; as well as suggesting a 2300-year radiocarbon period that modulates the 208-year period.  During the Upper Permian 240 million years ago, mineral layers created in the Castile Formation show cycles of 2,500 years.

Solar magnetic field.

The Sun's magnetic field structures its atmosphere and outer layers all the way through the corona and into the solar wind. Its spatiotemporal variations lead to various measurable solar phenomena. Other solar phenomena are closely related to the cycle, which serves as the energy source and dynamical engine for the former.

Effects.

Solar.

Surface magnetism.

Sunspots eventually decay, releasing magnetic flux in the photosphere. This flux is dispersed and churned by turbulent convection and solar large-scale flows. These transport mechanisms lead to the accumulation of magnetized decay products at high solar latitudes, eventually reversing the polarity of the polar fields (notice how the blue and yellow fields reverse in the Hathaway/NASA/MSFC graph above).  The dipolar component of the solar magnetic field reverses polarity around the time of solar maximum and reaches peak strength at the solar minimum.

Space.

Spacecraft.

CMEs (coronal mass ejections) produce a radiation flux of high-energy protons, sometimes known as solar cosmic rays. These can cause radiation damage to electronics and solar cells in satellites. Solar proton events also can cause single-event upset (SEU) events on electronics; at the same, the reduced flux of galactic cosmic radiation during solar maximum decreases the high-energy component of particle flux.  CME radiation is dangerous to astronauts on a space mission who are outside the shielding produced by the Earth's magnetic field. Future mission designs ("e.g.", for a Mars Mission) therefore incorporate a radiation-shielded "storm shelter" for astronauts to retreat to during such an event.  Gleißberg developed a CME forecasting method that relies on consecutive cycles.  On the positive side, the increased irradiance during solar maximum expands the envelope of the Earth's atmosphere, causing low-orbiting space debris to re-enter more quickly.

Galactic cosmic ray flux.

The outward expansion of solar ejecta into interplanetary space provides overdensities of plasma that are efficient at scattering high-energy cosmic rays entering the solar system from elsewhere in the galaxy. The frequency of solar eruptive events is modulated by the cycle, changing the degree of cosmic ray scattering in the outer solar system accordingly. As a consequence, the cosmic ray flux in the inner Solar System is anticorrelated with the overall level of solar activity. This anticorrelation is clearly detected in cosmic ray flux measurements at the Earth's surface.  Some high-energy cosmic rays entering Earth's atmosphere collide hard enough with molecular atmospheric constituents that they occasionally cause nuclear spallation reactions. Fission products include radionuclides such as C and Be that settle on the Earth's surface. Their concentration can be measured in tree trunks or ice cores, allowing a reconstruction of solar activity levels into the distant past. Such reconstructions indicate that the overall level of solar activity since the middle of the twentieth century stands amongst the highest of the past 10,000 years, and that epochs of suppressed activity, of varying durations have occurred repeatedly over that time span.

Atmospheric.

Solar irradiance.

The total solar irradiance (TSI) is the amount of solar radiative energy incident on the Earth's upper atmosphere. TSI variations were undetectable until satellite observations began in late 1978. A series of radiometers were launched on satellites from the 1970s to the 2000s. TSI measurements varied from 1360 to 1370 W/m across ten satellites. One of the satellites, the ACRIMSAT was launched by the ACRIM group. The controversial 1989–1991 "ACRIM gap" between non-overlapping ACRIM satellites was interpolated by the ACRIM group into a composite showing +0.037%/decade rise. Another series based on the ACRIM data is produced by the PMOD group and shows a −0.008%/decade downward trend. This 0.045%/decade difference impacts climate models.  Solar irradiance varies systematically over the cycle, both in total irradiance and in its relative components (UV vs visible and other frequencies). The solar luminosity is an estimated 0.07 percent brighter during the mid-cycle solar maximum than the terminal solar minimum. Photospheric magnetism appears to be the primary cause (96%) of 1996–2013 TSI variation. The ratio of ultraviolet to visible light varies.  TSI varies in phase with the solar magnetic activity cycle with an amplitude of about 0.1% around an average value of about 1361.5 W/m (the "solar constant"). Variations about the average of up to −0.3% are caused by large sunspot groups and of +0.05% by large faculae and the bright network on a 7-10-day timescale (see TSI variation graphics). Satellite-era TSI variations show small but detectable trends.  TSI is higher at solar maximum, even though sunspots are darker (cooler) than the average photosphere. This is caused by magnetized structures other than sunspots during solar maxima, such as faculae and active elements of the "bright" network, that are brighter (hotter) than the average photosphere. They collectively overcompensate for the irradiance deficit associated with the cooler, but less numerous sunspots. The primary driver of TSI changes on solar rotational and sunspot cycle timescales is the varying photospheric coverage of these radiatively active solar magnetic structures.  Energy changes in UV irradiance involved in production and loss of ozone have atmospheric effects. The 30 HPa Atmospheric pressure level changed height in phase with solar activity during solar cycles 20–23. UV irradiance increase caused higher ozone production, leading to stratospheric heating and to poleward displacements in the stratospheric and tropospheric wind systems.

Short-wavelength radiation.

With a temperature of 5870 K, the photosphere emits a proportion of radiation in the extreme ultraviolet (EUV) and above. However, hotter upper layers of the Sun's atmosphere (chromosphere and corona) emit more short-wavelength radiation. Since the upper atmosphere is not homogeneous and contains significant magnetic structure, the solar ultraviolet (UV), EUV and X-ray flux varies markedly over the cycle.  The photo montage to the left illustrates this variation for soft X-ray, as observed by the Japanese satellite Yohkoh from after August 30, 1991, at the peak of cycle 22, to September 6, 2001, at the peak of cycle 23. Similar cycle-related variations are observed in the flux of solar UV or EUV radiation, as observed, for example, by the SOHO or TRACE satellites.  Even though it only accounts for a minuscule fraction of total solar radiation, the impact of solar UV, EUV and X-ray radiation on the Earth's upper atmosphere is profound. Solar UV flux is a major driver of stratospheric chemistry, and increases in ionizing radiation significantly affect ionosphere-influenced temperature and electrical conductivity.

Solar radio flux.

Emission from the Sun at centimetric (radio) wavelength is due primarily to coronal plasma trapped in the magnetic fields overlying active regions. The F10.7 index is a measure of the solar radio flux per unit frequency at a wavelength of 10.7 cm, near the peak of the observed solar radio emission. F10.7 is often expressed in SFU or solar flux units (1 SFU = 10 W m Hz). It represents a measure of diffuse, nonradiative coronal plasma heating. It is an excellent indicator of overall solar activity levels and correlates well with solar UV emissions.  Sunspot activity has a major effect on long distance radio communications, particularly on the shortwave bands although medium wave and low VHF frequencies are also affected. High levels of sunspot activity lead to improved signal propagation on higher frequency bands, although they also increase the levels of solar noise and ionospheric disturbances. These effects are caused by impact of the increased level of solar radiation on the ionosphere.  10.7 cm solar flux could interfere with point-to-point terrestrial communications.

Clouds.

Speculations about the effects of cosmic-ray changes over the cycle potentially include: Later papers showed that production of clouds via cosmic rays could not be explained by nucleation particles. Accelerator results failed to produce sufficient, and sufficiently large, particles to result in cloud formation; this includes observations after a major solar storm. Observations after Chernobyl do not show any induced clouds.

Terrestrial.

Organisms.

The impact of the solar cycle on living organisms has been investigated (see chronobiology). Some researchers claim to have found connections with human health.  The amount of ultraviolet UVB light at 300 nm reaching the Earth varies by as much as 400% over the solar cycle due to variations in the protective ozone layer. In the stratosphere, ozone is continuously regenerated by the splitting of O molecules by ultraviolet light. During a solar minimum, the decrease in ultraviolet light received from the Sun leads to a decrease in the concentration of ozone, allowing increased UVB to reach the Earth's surface.

Radio communication.

Skywave modes of radio communication operate by bending (refracting) radio waves (electromagnetic radiation) through the Ionosphere. During the "peaks" of the solar cycle, the ionosphere becomes increasingly ionized by solar photons and cosmic rays. This affects the propagation of the radio wave in complex ways that can either facilitate or hinder communications. Forecasting of skywave modes is of considerable interest to commercial marine and aircraft communications, amateur radio operators and shortwave broadcasters. These users occupy frequencies within the High Frequency or 'HF' radio spectrum that are most affected by these solar and ionospheric variances. Changes in solar output affect the maximum usable frequency, a limit on the highest frequency usable for communications.

Climate.

Both long-term and short-term variations in solar activity are proposed to potentially affect global climate, but it has proven challenging to show any link between solar variation and climate.  Early research attempted to correlate weather with limited success, followed by attempts to correlate solar activity with global temperature. The cycle also impacts regional climate. Measurements from the SORCE's Spectral Irradiance Monitor show that solar UV variability produces, for example, colder winters in the U.S. and northern Europe and warmer winters in Canada and southern Europe during solar minima.  Three proposed mechanisms mediate solar variations' climate impacts:  The sunspot cycle variation of 0.1% has small but detectable effects on the Earth's climate. Camp and Tung suggest that solar irradiance correlates with a variation of 0.18 K ±0.08 K (0.32 °F ±0.14 °F) in measured average global temperature between solar maximum and minimum.  Other effects include one study which found a relationship with wheat prices, and another one that found a weak correlation with the flow of water in the Paraná River. Eleven-year cycles have been found in tree-ring thicknesses and layers at the bottom of a lake hundreds of millions of years ago.  The current scientific consensus, most specifically that of the IPCC, is that solar variations only play a marginal role in driving global climate change, since the measured magnitude of recent solar variation is much smaller than the forcing due to greenhouse gases. Also, average solar activity in the 2010s was no higher than in the 1950s (see above), whereas average global temperatures had risen markedly over that period. Otherwise, the level of understanding of solar impacts on weather is low.  Solar cycle also affects the orbital decay of Low Earth Orbiting (LEO) objects by affecting the density at the upper thermospheric levels.

Solar dynamo.

The 11-year sunspot cycle is thought to be one-half of a 22-year Babcock–Leighton solar dynamo cycle, which corresponds to an oscillatory exchange of energy between toroidal and poloidal solar magnetic fields which is mediated by solar plasma flows which also provides energy to the dynamo system at every step. At solar-cycle maximum, the external poloidal dipolar magnetic field is near its dynamo-cycle minimum strength, but an internal toroidal quadrupolar field, generated through differential rotation within the tachocline, is near its maximum strength. At this point in the dynamo cycle, buoyant upwelling within the Convection zone forces emergence of the toroidal magnetic field through the photosphere, giving rise to pairs of sunspots, roughly aligned east–west with opposite magnetic polarities. The magnetic polarity of sunspot pairs alternates every solar cycle, a phenomenon known as the Hale cycle.  During the solar cycle's declining phase, energy shifts from the internal toroidal magnetic field to the external poloidal field, and sunspots diminish in number. At solar minimum, the toroidal field is, correspondingly, at minimum strength, sunspots are relatively rare and the poloidal field is at maximum strength. During the next cycle, differential rotation converts magnetic energy back from the poloidal to the toroidal field, with a polarity that is opposite to the previous cycle. The process carries on continuously, and in an idealized, simplified scenario, each 11-year sunspot cycle corresponds to a change in the polarity of the Sun's large-scale magnetic field.  Solar dynamo models indicate that plasma flux transport processes in the solar interior such as differential rotation, meridional circulation and turbulent pumping play an important role in the recycling of the toroidal and poloidal components of the solar magnetic field (Hazra and Nandy 2016). The relative strengths of these flux transport processes also determine the "memory" of the solar cycle that plays an important role in physics-based predictions of the solar cycle. Yeates, Nandy and Mackay (2008) and Karak and Nandy (2012), in particular, utilized stochastically forced non-linear solar dynamo simulations to establish that the solar cycle memory is short, lasting over one cycle, thus implying accurate predictions are possible only for the next sunspot cycle and not beyond. This postulate of a short one cycle memory in the solar dynamo mechanism was later observationally verified by Muñoz-Jaramillo et al. (2013).  Although the tachocline has long been thought to be the key to generating the Sun's large-scale magnetic field, recent research has questioned this assumption. Radio observations of brown dwarfs have indicated that they also maintain large-scale magnetic fields and may display cycles of magnetic activity. The Sun has a radiative core surrounded by a convective envelope, and at the boundary of these two is the tachocline. However, brown dwarfs lack radiative cores and tachoclines. Their structure consists of a solar-like convective envelope that exists from core to surface. Since they lack a tachocline yet still display solar-like magnetic activity, it has been suggested that solar magnetic activity is only generated in the convective envelope.

Speculated influence of the planets.

It has long been theorized that the planets may have an influence on the solar cycle, with many speculative papers published through years. In 1974 there was a best-seller called "The Jupiter Effect" based on the idea. In 2012 a team led by José Abreu calculated the torque exerted by the planets on a non-spherical tachocline layer deep in the Sun and proposed an explanation of how the tiny tidal force can synchronize the solar dynamo. However, their results were shown to be an artifact of the incorrectly applied smoothing method leading to the aliasing. Moreover, the solar variability is known to be essentially stochastic and unpredictable beyond one solar cycle, which contradicts the idea of the deterministic planetary influence on solar dynamo. More recently, in Spring 2019 a team led by Frank Stefani published new results on the potential influence of the planetary tidal forces on the sun. The team of scientists compared historical observations of solar activity during the last thousand years with the evolution of planetary constellations, indicating that the two phenomena are statistically linked.

The solar cycle or solar magnetic activity cycle is a nearly periodic 11-year change in the Sun's activity measured in terms of variations in the number of observed sunspots on the solar surface. Sunspots have been observed since the early 17th century and the sunspot time series is the longest, continuously observed (recorded) time series of any natural phenomena. Accompanying the 11 year quasi-periodicity in sunspots, the large-scale dipolar (north-south) magnetic field component of the Sun also flips every 11 years, however, the peak in the dipolar field lags the peak in the sunspot number, with the former occurring at the minimum between two cycles. Levels of solar radiation and ejection of solar material, the number and size of sunspots, solar flares, and coronal loops all exhibit a synchronized fluctuation, from active to quiet to active again, with a period of 11 years. This cycle has been observed for centuries by changes in the Sun's appearance and by terrestrial phenomena such as auroras. Solar activity, driven both by the sunspot cycle and transient aperiodic processes govern the environment of the Solar System planets by creating space weather and impact space- and ground-based technologies as well as the Earth's atmosphere and also possibly climate fluctuations on scales of centuries and longer. Understanding and predicting the sunspot cycle remains one of the grand challenges in astrophysics with major ramifications for space science and the understanding of magnetohydrodynamic phenomena elsewhere in the Universe.

Schwabeův sluneční cyklus, Schwabe-Wolfův cyklus nebo cyklus slunečních skvrn je cyklus jedenáctileté aktivity Slunce objevený roku 1843 německým hvězdářem Heinrichem Schwabem. Roku 1849 byl položen základ pozorování počtu slunečních skvrn pozorovaných na naší nejbližší hvězdě. Z archeologických poznatků se ukazuje, že cyklus byl přítomný i před přibližně 300 milióny let. Cyklus je také spojen s otočením sluneční magnetické polarity. Sluneční cyklus není přesně 11 let dlouhý; již se také vyskytl 9letý či 14letý cyklus. Další možné cykly jsou předpokládány a je o nich více v článku sluneční variace.


Overview.

Ayers was born at Portsea, Portsmouth, Hampshire, England, the son of William Ayers, of the Portsmouth dockyard, and his wife Elizabeth, née Breakes. Educated at the Beneficial Society's School (Portsea) he entered a law office in 1832. He emigrated, as a carpenter, to South Australia in 1840 with his wife, Anne (née Potts) with free passages. Until 1845 he worked as a law clerk, he was then appointed secretary of the South Australian Mining Association's Burra Burra mines. Henry Roach was chief Captain, responsible for day-to-day operations, from 1847 to 1867. Within a year the mine employed over 1000 men. For nearly 50 years, Ayers was in control of this mine, initially as the secretary and later as the managing director. He made his wealth from the Burra Burra Copper Mines, which was known as the "Monster Mine", which secured the wealth of the colony of South Australia.

Politics.

On 9 March 1857 Ayers was elected to the first South Australian Legislative Council under responsible government, the youngest member elected. He was continuously a member for over 36 years. For many years the whole colony formed a single electorate for the council; on two occasions (1865 and 1873) Ayers headed the poll.  In March 1863 Ayers was selected as one of the three South Australian representatives at the inter-colonial conference on uniform tariffs and inland customs duties. He also represented the colony at several other conferences from 1864 to 1877. On 4 July 1863 Ayers became minister without portfolio in the first Dutton cabinet. This ministry resigned just 11 days later however, as council demanded that it should have an executive minister to represent the government and Dutton refused. Ayers formed his first ministry as Premier and Chief Secretary on 15 July 1863. The house was much divided and it was almost impossible to get business done. Ayers reconstructed his ministry on 22 July 1864 but was defeated, and resigned on 4 August 1864. The Blyth ministry which was then formed included Ayers as chief secretary, but did not survive a general election and resigned on 22 March 1865. When Dutton formed his second ministry Ayers had his old position as chief secretary, and still retaining that office, formed his third administration on 20 September 1865 which lasted just over a month. In spite of dissolutions it was found very difficult to get a workable house. There were 18 ministries tween July 1863 and July 1873. Ayers became the premier again from May 1867 to September 1868, October to November 1868, 27 January 1872 to March 1872, and with an entirely new team of ministers, from March 1872 to July 1873. He held the position of chief secretary in the Colton ministry from June 1876 to October 1877, his last term of office.  In 1881 Ayers was elected President of the South Australian Legislative Council, and until December 1893 carried out his duties with ability, impartiality and courtesy. He died in Adelaide on 11 June 1897. His wife had died in 1881, and he was survived by three sons and a daughter. He was created a CMG in 1870, knighted a KCMG in 1872, and raised to GCMG in 1894.

Legacy.

Apart from his mining interests, Ayers held important directorates and was for many years a member and chairman of the board of trustees of the Savings Bank of South Australia; he was re-appointed chairman only a few days before his death. He was the first Chairman of the South Australian Gas Company, from 1862 was a governor of the Adelaide Botanic Gardens, president of the South Australian Old Colonists' Association, and was for many years on the council of the University of Adelaide. He was in parliament for an unbroken term of 37 years and in no other Australian colony or state has a politician exercised so much influence or been in so many ministries while a member of the upper house. It is likely, however, that if Ayers had been in the House of Assembly he would have had more control of business, and his seven premierships would have been longer in duration and more fruitful in results. An address he gave on "Pioneer Difficulties on Founding South Australia" was published as a pamphlet in 1891.  Ayers resided in Ayers House from 1855 until 1897 and built it from a 9-room house into a grand mansion in the 1860s. The youngest child, Lucy, was born at Ayers House. During Sir Henry's parliamentary service, Ayers House was used for Cabinet meetings, parliamentary dinners, and grand balls.

Family.

Henry Ayers married Anne Potts (1812 – 13 August 1881) at Alverstoke around 1839. Anne was a sister of winemaker Frank Potts. They had four surviving sons and two daughters:

Sir Henry Ayers (now pron. "airs") (1 May 1821 – 11 June 1897) was the eighth Premier of South Australia, serving a record five times between 1863 and 1873.

Sir Henry Ayers (1. května 1821 Portsea, Portsmouth, Hampshire – 11. června 1897 Adelaide) byl premiér Jižní Austrálie; byl po něm pojmenován jeden ze státních symbolů Austrálie – monolit Uluru ("Ayers Rock").


Early life.

Vianney was born on 8 May 1786, in the French town of Dardilly, France (near Lyon), and was baptized the same day. His parents, Matthieu Vianney and his wife Marie (Belize), had six children, of whom John was the fourth. The Vianneys were devout Catholics who helped the poor. Vianney's paternal grandparents once gave hospitality to St. Benedict Joseph Labre, the patron saint of the homeless, who passed through Dardilly on his pilgrimage to Rome in 1770.  By 1790, the anticlerical Terror phase of the French Revolution forced many loyal priests to hide from the regime in order to carry out the sacraments in their parish. Even though to do so had been declared illegal, the Vianneys traveled to distant farms to attend Masses celebrated by priests on the run. Realizing that such priests risked their lives day by day, Vianney began to look upon them as heroes. He received his First Communion catechism instructions in a private home by two nuns whose communities had been dissolved during the Revolution. He made his First Communion at the age of 13 in a neighbor’s kitchen; during the Mass, the windows were covered so that the light of the candles could not be seen from the outside. His practice of the faith continued in secret, especially during his preparation for confirmation.  The Catholic Church was re-established in France in 1802 by Napoleon Bonaparte, resulting in religious peace throughout the country, culminating in a Concordat. By this time, Vianney was concerned about his future vocation and longed for an education. He was 20 when his father allowed him to leave the farm to be taught at a "presbytery-school" in the neighboring village of Écully, conducted by the Abbé Balley. The school taught arithmetic, history, geography and Latin. Vianney struggled with school, especially with Latin, since his past education had been interrupted by the French Revolution. Only because of Vianney's deepest desire to be a priest—and Balley's patience—did he persevere.  Vianney's studies were interrupted in 1809 when he was drafted into Napoleon's armies. He would have been exempt, as an ecclesiastical student, but Napoleon had withdrawn the exemption in certain dioceses because of his need for soldiers in his fight against Spain. Two days after he had to report at Lyons, he became ill and was hospitalized, during which time his draft left without him. Once released from the hospital, on 5 January, he was sent to Roanne for another draft. He went into a church to pray, and fell behind the group. He met a young man who volunteered to guide him back to his group, but instead led him deep into the mountains of Le Forez, to the village of Les Noes, where deserters had gathered. Vianney lived there for fourteen months, hidden in the byre attached to a farmhouse, and under the care of Claudine Fayot, a widow with four children. He assumed the name Jerome Vincent, and under that name, he opened a school for village children. Since the harsh weather isolated the town during the winter, the deserters were safe from gendarmes. However, after the snow melted, gendarmes came to the town constantly, searching for deserters. During these searches, Vianney hid inside stacks of fermenting hay in Fayot's barn.  An imperial proclamation in March 1810 granted amnesty to all deserters, enabling Vianney to go back legally to Écully, where he resumed his studies. He was tonsured in 1811, and in 1812 he went to the minor seminary at Verrières-en-Forez. In autumn of 1813, he was sent to the major seminary at Lyons. Considered too slow, he was returned to Abbé Balley. However, Balley persuaded the Vicar general that Vianney's piety was great enough to compensate for his ignorance, and the seminarian received minor orders and the subdiaconate on 2 July 1814, was ordained a deacon in June 1815, and was ordained priest on 12 August 1815 in the Couvent des Minimes de Grenoble. He said his first Mass the next day, and was appointed the assistant to Balley in Écully.

Curé (priest) of Ars.

In 1818, shortly after the death of Balley, Vianney was appointed parish priest of the parish of Ars, a town of 230 inhabitants. When Vianney's bishop first assigned him to Ars, he got lost trying to find the town. Two young men tending flocks in the fields pointed him in the right direction. With Catherine Lassagne and Benedicta Lardet, he established "La Providence", a home for girls.  As parish priest, Vianney realized that the Revolution's aftermath had resulted in religious ignorance and indifference, due to the devastation wrought on the Catholic Church in France. At the time, Sundays in rural areas were spent working in the fields, or dancing and drinking in taverns. Vianney spent time in the confessional and gave homilies against blasphemy and paganic dancing. If his parishioners did not give up this dancing, he refused them absolution.

Later years.

Vianney came to be known internationally, and people from distant places began travelling to consult him as early as 1827. "By 1855, the number of pilgrims had reached 20,000 a year. During the last ten years of his life, he spent 16 to 18 hours a day in the confessional. Even the bishop forbade him to attend the annual retreats of the diocesan clergy because of the souls awaiting him yonder". He spent at least 11 or 12 hours a day in the confessional during winter, and up to 16 in the summer.  In his article "How does the Church Respond to Suicide?" Shaun McAfee references an incident described in the book "Cure of Ars:" "...a woman...told...Vianney that she was devastated because her husband had committed suicide. She wanted to approach the great priest but his line often lasted for hours and she could not reach him. She was ready to give up and in a moment of mystical insight that only a great saint can receive...Vianney exclaimed through the crowd, “He is saved!” The woman was incredulous so the saint repeated, stressing each word, “I tell you he is saved. He is in Purgatory, and you must pray for him. Between the parapet of the bridge and the water he had time to make an act of contrition.”Vianney had a great devotion to St. Philomena. Vianney regarded her as his guardian and erected a chapel and shrine in honor of the saint. During May 1843, Vianney fell so ill he thought that his life was coming to its end. Vianney attributed his cure to her intercession.  Vianney yearned for the contemplative life of a monk, and four times ran away from Ars, the last time in 1853. He was a champion of the poor as a Franciscan tertiary and was a recipient of the coveted French Legion of Honour.

Death and veneration.

On 4 August 1859, Vianney died at the age of 73. The bishop presided over his funeral with 300 priests and more than 6,000 people in attendance. Before he was buried, Vianney's body was fitted with a wax mask.  On 3 October 1874 Pope Pius IX proclaimed him "venerable"; on 8 January 1905, Pope Pius X declared him Blessed and proposed him as a model to the parochial clergy. In 1925 John Mary Vianney was canonized by Pope Pius XI, who in 1929 made him patron saint of parish priests. In 1928 his feast day was inserted into the General Roman Calendar for celebration on 9 August. Pope John XXIII's 1960 revision, in which the Vigil of Saint Lawrence had a high rank, moved the feast to 8 August. Finally, the 1969 revision placed it on 4 August, the day of his death.  In 1959, to commemorate the centenary of John Vianney's death, Pope John XXIII issued the encyclical letter "Sacerdotii nostri primordia". John Paul II visited Ars in person in 1986 in connection with the bicentenary of Vianney's birth and referred to the great saint as a "rare example of a pastor acutely aware of his responsibilities... and a sign of courage for those who today experience the grace of being called to the priesthood."  In honor of the 150th anniversary of Vianney's death, Pope Benedict XVI declared a Year of the Priest, running from the Feast of the Sacred Heart 2009–2010.  The Vatican Postal Service issued a set of stamps to commemorate the 150th Anniversary. With the following words on 16 June 2009, Benedict XVI officially marked the beginning of the year dedicated to priests, "...On the forthcoming Solemnity of the Most Sacred Heart of Jesus, Friday 19 June 2009 – a day traditionally devoted to prayer for the sanctification of the clergy –, I have decided to inaugurate a ‘Year of the Priest’ in celebration of the 150th anniversary of the "dies natalis" of John Mary Vianney, the Patron Saint of parish priests worldwide..."  Pope Benedict XVI declared 19 June 2009 – 19 June 2010 the Year of the Priests to encourage priests to strive for spiritual perfection. In the Holy Father's words the Curé d'Ars is "a true example of a pastor at the service of Christ's flock."  There are statues of Vianney in many French churches and in Catholic churches throughout the world. Also, many parishes founded in the twentieth and twenty-first centuries are named after him. Some relics are kept in the Church of Notre-Dame de la Salette in Paris.

"Heart of a Priest" relic tour.

In November 2018, Vianney's heart was transported to the United States for a 6-month nationwide tour. As Joe Bollig explained in his article detailing the relic's unexpected stop in Kansas City, "The heart receives special veneration because in Scripture it is considered to be a person’s hidden center of emotional, intellectual and moral activity. Saint John Vianney is said to have lived his life according to the heart of Christ and united his heart to Christ’s."By the end of the tour, "the relic [had] traveled almost 36,000 miles — almost one and a half times the circumference of the Earth — and was available for over 1,200 hours of public veneration."

Notable institutions carrying his name.

There are dozens of institutions, including schools, seminaries, and churches named after Vianney in countries including Belize, Brazil, Canada, Guatemala, Haiti, Ireland, India, Pakistan, Philippines, England, United States, Nigeria, South Africa, New Zealand and Australia. There is also a St John Vianney church and school in Edinburgh, Scotland

Jean-Marie Vianney, (8 May 1786 – 4 August 1859), commonly known in English as Saint John Vianney, was a French parish priest who is venerated in the Catholic Church as a saint and as the patron saint of parish priests. He is often referred to as the "Curé d'Ars" (i.e. the parish priest of Ars), internationally known for his priestly and pastoral work in his parish in Ars, France, because of the radical spiritual transformation of the community and its surroundings. Catholics attribute this to his saintly life, mortification, persevering ministry in the sacrament of confession, and ardent devotion to the Blessed Virgin Mary. His feast day is 4 August.

Svatý Jean Baptiste Marie Vianney (8. května 1786, Dardilly, Francie – 4. srpna 1859) byl francouzský diecézní kněz, dnes prohlášen za svatého a navíc patrona kněží v duchovní správě. Často je znám jako svatý farář z Arsu podle místa, kde působil. Stal se mezinárodně slavným pro svou kněžskou a pastýřskou práci ve své farnosti díky snaze ji a její okolí radikálně duchovně přetvořit. V souvislosti se 150. výročím jeho úmrtí vyhlásil v roce 2009 papež Benedikt XVI. "rok kněží". V roce 1925 byl papežem Piem XI. svatořečen a v roce 1929 prohlášen patronem kněží.


Description.

"Yanoconodon" was a small mammal, barely 5 inches (13 centimetres) long. It had a sprawling posture, and although previously inferred to be semi-aquatic, direct study of its postcrania indicates that "Yanoconodon" was likely a terrestrial mammal, and that it has features in common with digging, arboreal, and semiaquatic mammals. "Yanocodon" had lumbar ribs, a feature not seen in modern mammals. The closely related eutriconodont "Jeholodens" lacks these lumbar ribs, and it has been suggested that this morphological difference is due to changes in the Hox genes, specifically in the "Hox10" group. In mice, a triple mutation knocking out all "Hox10" genes leads to the presence of lumbar ribs, supporting the theory that these genes have evolved the ability to repress the ancestral lumbar morphology seen in the Eutriconodonts.  The "Yanoconodon" holotype is so well preserved that scientists were able to examine tiny bones of the middle ear. These are of particular interest because of their "transitional" state: "Yanoconodon" has fundamentally modern middle ear bones, but these are still attached to the jaw by an ossified Meckel's cartilage. This is a feature retained from earlier stem mammals, and illustrates the transition from a basal tetrapod jaw and ear, to a mammalian one in which the middle ear bones are fully separate from the jaw. Despite this feature "Yanoconodon" is a true mammal"." It is thought that the feature was retained during early embryo development, whereas it is lost in most other mammal groups. The intermediate anatomy of the middle ear of "Yanocodon" is said to be a "Rosetta Stone" of mammalian middle ear evolution.

Yanoconodon is a monotypic genus of extinct early mammal whose representative species Yanoconodon allini lived during the Mesozoic in what is now China. The holotype fossil of "Yanoconodon" was excavated in the Yan Mountains about 300 kilometres from Beijing in the Qiaotou member of the Huajiying Formation (which the original authors considered part of the Yixian Formation) of Hebei Province, China, and is therefore of uncertain age. The Qiaotou Member may correlate with the more well-known Early Cretaceous Yixian Formation, and so probably dates to around 122 Ma ago.

Yanoconodon byl spodnokřídový savec z řádu Eutriconodonta. Jedná se o blízkého příbuzného rodu "Jeholodens", se kterým patří do čeledi Jeholodentidae. Janokonodontovy fosílie pocházejí z čínského souvrství Yixian (provincie Hebei). Tento pravěký savec byl dlouhý přibližně 15 cm a vážil jen kolem 30 gramů. Živil se zřejmě především bezobratlými.


Course.

The river flows in a great arc, first zigzagging north and then north-east, then turning east and finally south-east. It serves as a border for about, separating South Africa to the southeast from Botswana to the northwest and Zimbabwe to the north. Two of its tributaries, the Marico River and the Crocodile River join, at which point the name changes to Limpopo River. There are several rapids as the river falls off Southern Africa's inland escarpment.  The Notwane River is a major tributary of the Limpopo, rising on the edge of the Kalahari Desert in Botswana and flowing in a north-easterly direction. The main tributary of the Limpopo, the Olifants River (Elephant River), contributes around 1,233 million m of water per year. Other major tributaries include the Shashe River, Mzingwane River, Crocodile River, Mwenezi River and Luvuvhu River.  In the north-eastern corner of South Africa the river borders the Kruger National Park.  The port town of Xai-Xai, Mozambique is on the river near the mouth. Below the Olifants, the river is permanently navigable to the sea, though a sandbar prevents access by large ships except at high tide.

Basin characteristics.

The waters of the Limpopo flow sluggishly, with considerable silt content. Rudyard Kipling's characterization of the river as the "great grey-green, greasy Limpopo River, all set about with fever-trees," where the "Bi-Coloured Python Rock-Snake" dwells in the "Just So Stories" is apt. Rainfall is seasonal and unreliable: in dry years, the upper parts of the river flow for 40 days or less. The upper part of the drainage basin, in the Kalahari Desert, is arid but conditions become less arid further downriver. The next reaches drain the Waterberg Massif, a biome of semi-deciduous forest and low-density human population. About 14 million people live in the Limpopo basin. The fertile lowlands support a denser population. Flooding during the rainy season is an occasional problem in the lower reaches. During February 2000 heavy rainfalls (due to a cyclone) caused the catastrophic 2000 Mozambique flood.  The highest concentration of hippopotamus in the Limpopo River is found between the Mokolo and the Mogalakwena Rivers.  There is a lot of mining activity in the Limpopo River basin with about 1,900 mines, not counting about 1,700 abandoned mines.

History.

Vasco da Gama on his first expedition, was probably among the first Europeans to sight the river, when he anchored off the mouth in 1498. However, there has been human habitation in the region since time immemorial — sites in the Makapans Valley near Mokopane contain Australopithecus fossils from 3.5 million years ago. St Vincent Whitshed Erskine, later Surveyor General for South Africa, traveled to the mouth of the river in 1868-69.  A Zambezi shark ("Carcharhinus leucas") was caught hundreds of kilometres upriver at the confluence of the Limpopo and Luvuvhu Rivers in July 1950. Zambezi sharks tolerate fresh water and can travel far up the Limpopo.  In 2013, approximately 15,000 Nile crocodiles were released into the river from flood gates at the nearby Rakwena Crocodile Farm.

The Limpopo River rises in South Africa, and flows generally eastwards through Mozambique to the Indian Ocean. The term Limpopo is derived from Rivombo (Livombo/Lebombo), a group of Tsonga settlers led by Hosi Rivombo who settled in the mountainous vicinity and named the area after their leader. The river is approximately long, with a drainage basin in size. The mean discharge measured over a year is 170 m/s (6,200 cu ft/s) at its mouth. The Limpopo is the second largest river in Africa that drains to the Indian Ocean, after the Zambezi River.

Limpopo (,, ), také nazývaná Krokodýlí řeka, je řeka v jižní Africe. Pramení na území Botswany, na středním toku tvoří státní hranici Jihoafrické republiky s Botswanou a se Zimbabwe a na dolním toku protéká Mosambikem. Je 1600 km dlouhá. Povodí má rozlohu 440 000 km2.


Description.

A transmitter can be a separate piece of electronic equipment, or an electrical circuit within another electronic device. A transmitter and a receiver combined in one unit is called a transceiver. The term transmitter is often abbreviated "XMTR" or "TX" in technical documents. The purpose of most transmitters is radio communication of information over a distance. The information is provided to the transmitter in the form of an electronic signal, such as an audio (sound) signal from a microphone, a video (TV) signal from a video camera, or in wireless networking devices, a digital signal from a computer. The transmitter combines the information signal to be carried with the radio frequency signal which generates the radio waves, which is called the carrier signal. This process is called "modulation". The information can be added to the carrier in several different ways, in different types of transmitters. In an amplitude modulation (AM) transmitter, the information is added to the radio signal by varying its amplitude. In a frequency modulation (FM) transmitter, it is added by varying the radio signal's frequency slightly. Many other types of modulation are also used.  The radio signal from the transmitter is applied to the antenna, which radiates the energy as radio waves. The antenna may be enclosed inside the case or attached to the outside of the transmitter, as in portable devices such as cell phones, walkie-talkies, and garage door openers. In more powerful transmitters, the antenna may be located on top of a building or on a separate tower, and connected to the transmitter by a feed line, that is a transmission line.

Operation.

Electromagnetic waves are radiated by electric charges when they are accelerated. Radio waves, electromagnetic waves of radio frequency, are generated by time-varying electric currents, consisting of electrons flowing through a metal conductor called an antenna which are changing their velocity and thus accelerating. An alternating current flowing back and forth in an antenna will create an oscillating magnetic field around the conductor. The alternating voltage will also charge the ends of the conductor alternately positive and negative, creating an oscillating electric field around the conductor. If the frequency of the oscillations is high enough, in the radio frequency range above about 20 kHz, the oscillating coupled electric and magnetic fields will radiate away from the antenna into space as an electromagnetic wave, a radio wave.  A radio transmitter is an electronic circuit which transforms electric power from a power source into a radio frequency alternating current to apply to the antenna, and the antenna radiates the energy from this current as radio waves. The transmitter also impresses information such as an audio or video signal onto the radio frequency current to be carried by the radio waves. When they strike the antenna of a radio receiver, the waves excite similar (but less powerful) radio frequency currents in it. The radio receiver extracts the information from the received waves.

Components.

A practical radio transmitter mainly consists of the following parts:  In higher frequency transmitters, in the UHF and microwave range, free running oscillators are unstable at the output frequency. Older designs used an oscillator at a lower frequency, which was multiplied by frequency multipliers to get a signal at the desired frequency. Modern designs more commonly use an oscillator at the operating frequency which is stabilized by phase locking to a very stable lower frequency reference, usually a crystal oscillator.

Regulation.

Two radio transmitters in the same area that attempt to transmit on the same frequency will interfere with each other, causing garbled reception, so neither transmission may be received clearly. Interference with radio transmissions can not only have a large economic cost, it can be life-threatening (for example, in the case of interference with emergency communications or air traffic control). For this reason, in most countries, use of transmitters is strictly controlled by law. Transmitters must be licensed by governments, under a variety of license classes depending on use such as broadcast, marine radio, Airband, Amateur and are restricted to certain frequencies and power levels. A body called the International Telecommunications Union (ITU) allocates the frequency bands in the radio spectrum to various classes of users. In some classes, each transmitter is given a unique call sign consisting of a string of letters and numbers which must be used as an identifier in transmissions. The operator of the transmitter usually must hold a government license, such as a general radiotelephone operator license, which is obtained by passing a test demonstrating adequate technical and legal knowledge of safe radio operation.  Exceptions to the above regulations allow the unlicensed use of low-power short-range transmitters in consumer products such as cell phones, cordless telephones, wireless microphones, walkie-talkies, Wi-Fi and Bluetooth devices, garage door openers, and baby monitors. In the US, these fall under Part 15 of the Federal Communications Commission (FCC) regulations. Although they can be operated without a license, these devices still generally must be type-approved before sale.

History.

The first primitive radio transmitters (called spark gap transmitters) were built by German physicist Heinrich Hertz in 1887 during his pioneering investigations of radio waves. These generated radio waves by a high voltage spark between two conductors. Beginning in 1895, Guglielmo Marconi developed the first practical radio communication systems using these transmitters, and radio began to be used commercially around 1900. Spark transmitters could not transmit audio (sound) and instead transmitted information by radiotelegraphy, the operator tapped on a telegraph key which turned the transmitter on and off to produce pulses of radio waves spelling out text messages in Morse code. These spark-gap transmitters were used during the first three decades of radio (1887-1917), called the wireless telegraphy or "spark" era. Because they generated damped waves, spark transmitters were electrically "noisy". Their energy was spread over a broad band of frequencies, creating radio noise which interfered with other transmitters. Damped wave emissions were banned by international law in 1934.  Two short-lived competing transmitter technologies came into use after the turn of the century, which were the first continuous wave transmitters: the arc converter (Poulsen arc) in 1904 and the Alexanderson alternator around 1910, which were used into the 1920s.  All these early technologies were replaced by vacuum tube transmitters in the 1920s, which used the feedback oscillator invented by Edwin Armstrong and Alexander Meissner around 1912, based on the Audion (triode) vacuum tube invented by Lee De Forest in 1906. Vacuum tube transmitters were inexpensive and produced continuous waves, and could be easily modulated to transmit audio (sound) using amplitude modulation (AM). This made AM radio broadcasting possible, which began in about 1920. Practical frequency modulation (FM) transmission was invented by Edwin Armstrong in 1933, who showed that it was less vulnerable to noise and static than AM. The first FM radio station was licensed in 1937. Experimental television transmission had been conducted by radio stations since the late 1920s, but practical television broadcasting didn't begin until the late 1930s. The development of radar during World War II motivated the evolution of high frequency transmitters in the UHF and microwave ranges, using new active devices such as the magnetron, klystron, and traveling wave tube.  The invention of the transistor allowed the development in the 1960s of small portable transmitters such as wireless microphones, garage door openers and walkie-talkies. The development of the integrated circuit (IC) in the 1970s made possible the current proliferation of wireless devices, such as cell phones and Wifi networks, in which integrated digital transmitters and receivers (wireless modems) in portable devices operate automatically, in the background, to exchange data with wireless networks.  The need to conserve bandwidth in the increasingly congested radio spectrum is driving the development of new types of transmitters such as spread spectrum, trunked radio systems and cognitive radio. A related trend has been an ongoing transition from analog to digital radio transmission methods. Digital modulation can have greater spectral efficiency than analog modulation; that is it can often transmit more information (data rate) in a given bandwidth than analog, using data compression algorithms. Other advantages of digital transmission are increased noise immunity, and greater flexibility and processing power of digital signal processing integrated circuits.

In electronics and telecommunications a transmitter or radio transmitter is an electronic device which produces radio waves with an antenna. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating current, the antenna radiates radio waves.

Rádiový vysílač je elektronické zařízení, které pomocí antény vyzařuje elektromagnetický signál, který může být přijat rádiovým přijímačem. V České republice máme takovýchto vysílačů několik.


Background.

Mercia was the dominant kingdom in southern England in the eighth century and maintained its position until it suffered a decisive defeat by Wessex at the Battle of Ellandun in 825. Thereafter the two kingdoms became allies, which was to be an important factor in English resistance to the Vikings. In 865 the Danish Viking Great Heathen Army landed in East Anglia and used this as a starting point for an invasion. The East Anglians were forced to pay off the Vikings, who invaded Northumbria the following year. They appointed a puppet king in 867, and then moved on Mercia, where they spent the winter

Childhood.

Edward's parents, Alfred and Ealhswith, married in 868. Her father was Æthelred Mucel, Ealdorman of the Gaini, and her mother, Eadburh, was a member of the Mercian royal family. Alfred and Ealhswith had five children who survived childhood. The oldest was Æthelflæd, who married Æthelred, Lord of the Mercians, and ruled as Lady of the Mercians after his death. Edward was next, and the second daughter, Æthelgifu, became abbess of Shaftesbury. The third daughter, Ælfthryth, married Baldwin, Count of Flanders, and the younger son, Æthelweard, was given a scholarly education, including learning Latin. This would usually suggest that he was intended for the church, but it is unlikely in Æthelweard's case as he later had sons. There were also an unknown number of children who died young. Neither part of

Ætheling.

As a son of a king, Edward was an ætheling, a prince of the royal house who was eligible for kingship. Even though he had the advantage of being the eldest son of the reigning king, his accession was not assured as he had cousins who had a strong claim to the throne. Æthelhelm and Æthelwold were sons of Æthelred, Alfred's older brother and predecessor as king, but they had been passed over because they were infants when their father died. Asser gives more information about Edward's childhood and youth than is known about other Anglo-Saxon princes, providing details about the training of a prince in a period of Carolingian influence, and Yorke suggests that we may know so much due to Alfred's efforts to portray his son as the most throneworthy ætheling.  Æthelhelm is only recorded in Alfred's will of the mid-880s, and probably died at some time in the next decade, but Æthelwold is listed above Edward in the only charter where he appears, probably indicating a higher status. Æthelwold may also have had an advantage because his mother Wulfthryth witnessed a charter as queen, whereas Edward's mother Ealhswith never had a higher status than king's wife. However, Alfred was in a position to give his own son considerable advantages. In his will, he left only a handful of estates to his brother's sons, and the bulk of his property to Edward, including all his booklands (land vested in a charter which could be alienated by the holder, as opposed to folkland, which had to pass to heirs of the body) in Kent. Alfred also advanced men who could be depended on to support his plans for his succession, such as his brother-in-law, a Mercian ealdorman called Æthelwulf, and his son-in-law Æthelred. Edward witnessed several of his father's charters, and often accompanied him on royal peregrinations. In a Kentish charter of 898 Edward witnessed as "rex Saxonum", suggesting that Alfred may have followed the strategy adopted by his grandfather Egbert of strengthening his son's claim to succeed to

Æthelwold's revolt.

Alfred died on 26 October 899 and Edward succeeded to the throne, but Æthelwold disputed the succession. He seized the royal estates of Wimborne, symbolically important as the place where his father was buried, and Christchurch, both in Dorset. Edward marched with his army to the nearby Iron Age hillfort at Badbury Rings. Æthelwold declared that he would live or die at Wimborne, but then left in the night and rode to Northumbria, where the Danes accepted him as king. Edward was crowned on 8June 900 at Kingston upon Thames.

King of the Anglo-Saxons.

In London in 886 Alfred had received the formal submission of "all the English people that were not under subjection to the Danes", and thereafter he adopted the title "Anglorum Saxonum rex" (King of the Anglo-Saxons), which is used in his later charters and all but two of Edward's. This is seen by Keynes as "the invention of a wholly new and distinctive polity", covering both West Saxons and Mercians, which was inherited by Edward with the support of Mercians at the West Saxon court, of whom the most important was Plegmund, Archbishop of Canterbury. In 903 Edward issued several charters concerning land in Mercia. Three of them are witnessed by the Mercian leaders and their daughter Ælfwynn, and they all contain a statement that Æthelred and Æthelflæd "then held rulership and power over the race of the Mercians, under the aforesaid king". Other charters were issued by the Mercian leaders which did not contain any acknowledgment of Edward's authority, but they did not issue their own coinage. This view of Edward's status is accepted by Martin

Conquest of the southern Danelaw.

No battles are recorded between the Anglo-Saxons and the Danish Vikings for several years after the Battle of the Holme, but in 906 Edward agreed peace with the East Anglian and Northumbrian Danes, suggesting that there had been conflict. According to one version of the "Anglo-Saxon Chronicle" he made peace "of necessity", which implies that he was forced to buy them off. He encouraged Englishmen to purchase land in Danish territory, and two charters survive relating to estates in Bedfordshire and Derbyshire. In 909 Edward sent a combined West Saxon and Mercian army which harassed the Northumbrian Danes, and seized the bones of the Northumbrian royal saint Oswald from Bardney Abbey in Lincolnshire. Oswald was translated to a new Mercian minster established by Æthelred and Æthelflæd in Gloucester and the Danes were compelled to accept peace on Edward's terms. In the following year, the Northumbrian Danes retaliated by raiding Mercia, but on their way home they were met by a combined Mercian and West Saxon army at the Battle of Tettenhall, where the Vikings suffered a disastrous defeat. After that, the Northumbrian Danes never ventured south of the River Humber, and Edward and his Mercian allies were able to concentrate on conquering the southern Danelaw in East Anglia and the Five Boroughs of Viking east Mercia: Derby, Leicester, Lincoln, Nottingham and Stamford.  In 911 Æthelred, Lord of the Mercians, died, and Edward took control of the Mercian lands around London and Oxford. Æthelred was succeeded as ruler by his widow Æthelflæd as Lady of the Mercians, and she had probably been acting as ruler for several years as Æthelred seems to have been incapacitated in later life.  Edward and Æthelflæd then began the construction of fortresses to guard against Viking attacks and protect territory captured from them. In November 911, he constructed a fort on the north bank of the River Lea at Hertford to guard against attack by the Danes of Bedford and Cambridge. In 912, he marched with his army to Maldon in Essex, and ordered the building of a fort at Witham and a second fort at Hertford, which protected London from attack and encouraged many English living under Danish rule in Essex to submit to him. In 913 there was a pause in his activities, although Æthelflæd continued her fortress building in Mercia.  In 914, a Viking army sailed from Brittany and ravaged the Severn estuary. It then attacked Ergyng in south-east Wales (now Archenfield in Herefordshire) and captured the Bishop, referred to as Cameleac, Cimeliauc and Cyfeilliog, depending on the source. Edward ransomed him for the large sum of forty pounds of silver. The Vikings

Coinage.

The principal currency in later Anglo-Saxon England was the silver penny, and some coins carried a stylised portrait of the king. Edward's coins had "EADVVEARD REX" on the obverse and the name of the moneyer on the reverse. The places of issue were not shown in his reign, but they were in that of his son Æthelstan, allowing the location of many moneyers of Edward's reign to be established. There were mints in Bath, Canterbury, Chester, Chichester, Derby, Exeter, Hereford, London,

Church.

In 908, Plegmund conveyed the alms of the English king and people to the Pope, the first visit to Rome by an Archbishop of Canterbury for almost a century, and the journey may have been to seek papal approval for a proposed re-organisation of the West Saxon sees. When Edward came to the throne Wessex had two dioceses, Winchester, held by Denewulf, and Sherborne, held by Asser. In 908 Denewulf died and was replaced the following year by Frithestan; soon afterwards Winchester was divided into two sees, with the creation of the diocese of Ramsbury covering Wiltshire and Berkshire, while Winchester was left with Hampshire and Surrey. Forged charters date the division to 909, but this may not be correct. Asser died in the same year, and at some date between 909 and 918 Sherborne was divided into three sees, Crediton covering Devon and Cornwall, and Wells covering Somerset, leaving Sherborne with Dorset. The effect of the changes was to strengthen the status of Canterbury compared with Winchester and Sherborne, but the division may have been related to a change in the secular functions of West Saxon bishops, to become agents of royal government in shires rather than provinces, assisting in defence and taking part in shire courts.  At the beginning of Edward's reign, his mother Ealhswith founded the abbey of St Mary for nuns, known as the Nunnaminster, in Winchester. Edward's daughter Eadburh became a nun there,

Learning and culture.

The standard of Anglo-Saxon learning declined severely in the ninth century, particularly in Wessex, and Mercian scholars such as Plegmund played a major part in the revival of learning initiated by Alfred. Mercians were prominent at the courts of Alfred and Edward, and the Mercian dialect and scholarship commanded West Saxon respect. It is uncertain how far Alfred's programmes continued during his son's reign. English translations of works in Latin made during Alfred's reign continued to be copied, but few original works are known. The script known as Anglo-Saxon Square minuscule reached

Law and administration.

Almost all surviving charters from Edward's reign are later copies, and the only surviving original is not a charter of Edward himself, but a grant by Æthelred and Æthelflæd in 901. In the same year a meeting at Southampton was attended by his brother and sons, his household thegns and nearly all bishops, but no ealdormen. It was on this occasion that the king acquired land from the Bishop of Winchester for the foundation of the New Minster, Winchester. No charters survive for the period from 910 to the king's death in 924, much to the puzzlement and distress of historians. Charters were usually issued when the king made grants of land, and it is possible that Edward followed a policy of retaining property which came into his hands to

Later life.

According to the "Anglo-Saxon Chronicle", there was a general submission of rulers in Britain to Edward in 920: This passage was regarded as a straightforward report by most historians until the late twentieth century, and Frank Stenton observed that "each of the rulers named in this list had something definite to gain from an acknowledgement of Edward's overlordship". Since the 1980s this submission has been viewed with increasing scepticism, particularly as the passage in the "Chronicle" is the only evidence for it, unlike other submissions such as that one in 927 to Æthelstan, for which there is independent support from literary sources and coins. Alfred P. Smyth points out that Edward was not in a position to impose the same conditions on the Scots and the Northumbrians as he could on conquered Vikings, and argues that the "Chronicle" presented a treaty between kings as a submission to Wessex. Stafford observes that the rulers had met at Bakewell on the border between Mercia and

Reputation.

According to William of Malmesbury, Edward was "much inferior to his father in the cultivation of letters", but "incomparably more glorious in the power of his rule". Other medieval chroniclers expressed similar views, and he was generally seen as inferior in book learning, but superior in military success. John of Worcester described him as "the most invincible King Edward the Elder". However, even as war leader he was only one of a succession of successful kings; his achievements were overshadowed because he did not have a famous victory like Alfred's at Edington and Æthelstan's at Brunanburh, and William of Malmesbury qualified his praise of Edward by saying that "the chief prize of victory, in my judgment, is due to his father". Edward has also been overshadowed by chroniclers' admiration for his highly regarded sister, Æthelflæd.  A principal reason for the neglect of Edward is that very few

Marriages and children.

Edward had about fourteen children from three marriages.  He first married Ecgwynn around 893. Their children were:  In c. 900, Edward married Ælfflæd, daughter of Ealdorman Æthelhelm, probably of Wiltshire. Their children were:  Edward married for a third time, about 919, Eadgifu, the daughter of Sigehelm, Ealdorman of Kent. Their children were:

Edward the Elder (c. 874– 17 July 924) was King of the Anglo-Saxons from 899 until his death. He was the elder son of Alfred the Great and his wife Ealhswith. When Edward succeeded to the throne, he had to defeat a challenge from his cousin Æthelwold, who had a strong claim to the throne as the son of Alfred's elder brother and predecessor, Æthelred.

Eduard I. Starší (cca 870 – 17. července 924) byl králem Anglie v letech 899 až 924. Byl synem Alfréda Velikého a stal se anglickým králem po jeho smrti. Byl panovníkem v době, kdy se království Wessex transformovalo do království Anglie. I když byl označován jako král Anglie, území, které patřilo pod jeho správu, bylo mnohem menší než území současné Anglie.


Paleontology.

Two dinosaur-bearing formations are present on the island, both from the Upper Cretaceous: the Santa Marta Formation and the Snow Hill Island Formation. These are two of only three known formations to have dinosaur fossils in Antarctica.  The first dinosaur discovered in Antarctica was "Antarctopelta oliveroi", a medium-sized ankylosaur found on James Ross Island by Argentinian geologists Eduardo Olivero and Roberto Scasso in 1986. The dinosaur was recovered from the Campanian stage of the Upper Cretaceous Santa Marta Formation, about south of Santa Marta Cove on the north part of the island. The ankylosaur was not formally named until 2006. In December 2003, U.S. paleontologist Judd Case from Saint Mary's College of California and U.S. geologist James Martin from the South Dakota School of Mines & Technology discovered the bones of a theropod dinosaur on the island. Nicknamed "Naze" after the northerly Naze Peninsula on which it was found, the Late Cretaceous remains include an upper jaw and teeth, and most of the lower legs and feet. Little information is available, but the shape of the leg and feet indicate it was a runner, and the size indicates it was probably tall and weighed. This is the second Antarctic theropod discovered, after "Cryolophosaurus".  An ornithopod was found in the Snow Hill Island Formation by Argentine paleontologists Rodolfo Aníbal Coria and Juan José Moly in 2008. In 2013, Coria named it "Trinisaura santamartaensis".  In 2015, an iguanodontid found in 2002 by Fernando Novas was named "Morrosaurus antarcticus" by Sebastian Rozadilla, Federico Lisandro Agnolin, Fernando Emilio Novas, Alexis Rolando Aranciaga Mauro, Matthew J. Motta, Juan Manuel Lirio Marcelo and Pablo Isasi. The genus name refers to the site of El Morro on James Ross Island, where the remains of the species were found. The specific name refers to Antarctica.

Named features.

James Ross Island features several features named by various surveying and exploration groups.

James Ross Island is a large island off the southeast side and near the northeastern extremity of the Antarctic Peninsula, from which it is separated by Prince Gustav Channel. Rising to, it is irregularly shaped and extends in a north–south direction. It was charted in October 1903 by the Swedish Antarctic Expedition under Otto Nordenskiöld, who named it for Sir James Clark Ross, the leader of a British expedition to this area in 1842 that discovered and roughly charted a number of points along the eastern side of the island. The style, "James" Ross Island is used to avoid confusion with the more widely known Ross Island in McMurdo Sound.

Ostrov Jamese Rosse ( [ˌdžeimz ˌros ˈailənd]) je velký ostrov v Jižním oceánu u pobřeží Antarktidy, východně od nejsevernějšího výběžku Antarktického poloostrova, od kterého je oddělen průlivem prince Gustava. Ostrov Jamese Rosse ("James Ross Island") není totožný s mnohem známějším ostrovem v Rossově moři pojmenovaným Rossův ostrov ("Ross Island").