How often do solar flares occur?
24728109#45
Since superflares can occur on stars apparently equivalent in every way to the Sun, it is natural to ask if they can occur on the Sun itself. An estimate based on the original Kepler photometric studies suggested a frequency on solar-type stars (early G-type and rotation period more than 10 days) of once every 800 years for an energy of 10 erg and every 5000 years at 10 erg. One-minute sampling provided statistics for less energetic flares and gave a frequency of one flare of energy 10 erg every 5–600 years for a star rotating as slowly as the Sun; this would be rated as X100 on the solar flare scale. This is based on a straightforward comparison of the number of stars studied with the number of flares observed. An extrapolation of the empirical statistics for solar flares to an energy of 10 erg suggests a frequency of one in 10,000 years.
Superflare
54648#25
Other large solar flares also occurred on April 2, 2001 (X20), October 28, 2003 (X17.2 and 10), September 7, 2005 (X17), February 17, 2011 (X2), August 9, 2011 (X6.9), March 7, 2012 (X5.4), July 6, 2012 (X1.1). On July 6, 2012, a solar storm hit just after midnight UK time, when an X1.1 solar flare fired out of the AR1515 sunspot. Another X1.4 solar flare from AR 1520 region of the Sun, second in the week, reached the Earth on July 15, 2012 with a geomagnetic storm of G1–G2 level. A X1.8-class flare was recorded on October 24, 2012. There has been major solar flare activity in early 2013, notably within a 48-hour period starting on May 12, 2013, a total of four X-class solar flares were emitted ranging from an X1.2 and upwards of an X3.2, the latter of which was one of the largest year 2013 flares. Departing sunspot complex AR2035-AR2046 erupted on April 25, 2014 at 0032 UT, producing a strong X1.3-class solar flare and an HF communications blackout on the day-side of Earth. NASA's Solar Dynamics Observatory recorded a flash of extreme ultraviolet radiation from the explosion. The Solar Dynamics Observatory recorded an X9.3-class flare at around 1200 UTC on September 6, 2017.
Solar flare
58921#26
A solar flare is a phenomenon where the Sun suddenly releases a great amount of solar radiation, much more than normal. Solar flares are unlikely to cause any direct injury, but can destroy electrical equipment. The potential of solar storms to cause disaster was seen during the 1859 Carrington event, which disrupted the telegraph network, and the March 1989 geomagnetic storm which blacked out Quebec. Some major known solar flares include the X20 event on August 16, 1989, and a similar flare on April 2, 2001. The most powerful flare ever recorded occurred on November 4, 2003 (estimated at between X40 and X45).
Natural disaster
255297#14
Coronal mass ejections are often associated with other forms of solar activity, most notably:
The association of a CME with some of those phenomena is common but not fully understood. For example, CMEs and flares are normally closely related, but there was confusion about this point caused by the events originating beyond the limb. For such events no flare could be detected. Most weak flares do not have associated CMEs; most powerful ones do. Some CMEs occur without any flare-like manifestation, but these are the weaker and slower ones. It is now thought that CMEs and associated flares are caused by a common event (the CME peak acceleration and the flare impulsive phase generally coincide). In general, all of these events (including the CME) are thought to be the result of a large-scale restructuring of the magnetic field; the presence or absence of a CME during one of these restructures would reflect the coronal environment of the process (i.e., can the eruption be confined by overlying magnetic structure, or will it simply break through and enter the solar wind).
Coronal mass ejection
206555#23
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.
Solar cycle
28336780#4
In late October 2003, a series of large solar flares occurred. A X17.2-class flare ejected on 28 October 2003 produced auroras visible as far south as Florida and Texas. A G5 level geomagnetic storm blasted the Earth's magnetosphere the next two days. A few days later, the largest solar flare ever measured with instruments occurred on 4 November; initially measured at X28, it was later upgraded to an X45-class. This flare was not Earth-oriented and thus only resulted in high-latitude auroras. The whole sequence of events occurred from 28 October to 4 November is known as the Halloween Solar Storm.
Solar cycle 23
206550#2
Large solar flares often occur during a maximum. For example, the solar storm of 1859 struck the Earth with such intensity that the northern lights were visible as far from the poles as Cuba and Hawaii.
Solar maximum
54648#4
Solar flares affect all layers of the solar atmosphere (photosphere, chromosphere, and corona). The plasma medium is heated to tens of millions of Kelvin, while electrons, protons, and heavier ions are accelerated to near the speed of light. Flares produce electromagnetic radiation across the electromagnetic spectrum at all wavelengths, from radio waves to gamma rays. Most of the energy is spread over frequencies outside the visual range and so the majority of the flares are not visible to the naked eye and must be observed with special instruments. Flares occur in active regions around sunspots, where intense magnetic fields penetrate the photosphere to link the corona to the solar interior.
Flares are powered by the sudden (timescales of minutes to tens of minutes) release of magnetic energy stored in the corona. The same energy releases may produce coronal mass ejections (CMEs), although the relationship between CMEs and flares is still not well understood.
Solar flare
54648#8
Flares occur when accelerated charged particles, mainly electrons, interact with the plasma medium. Evidence suggests that the phenomenon of magnetic reconnection leads to this copious acceleration of charged particles.
On the Sun, magnetic reconnection may happen on solar arcades – a series of closely occurring loops following magnetic lines of force. These lines of force quickly reconnect into a lower arcade of loops leaving a helix of magnetic field unconnected to the rest of the arcade. The sudden release of energy in this reconnection is the origin of the particle acceleration. The unconnected magnetic helical field and the material that it contains may violently expand outwards forming a coronal mass ejection. This also explains why solar flares typically erupt from active regions on the Sun where magnetic fields are much stronger.
Solar flare
12728898#44
A prominence eruption producing a CME shot off the east limb (left side) of the Sun on April 16, 2012. Such eruptions are often associated with solar flares, and in this case an M1.7 class (medium-sized) flare occurred at the same time, peaking at 1:45 PM EDT and 17.45 UTC. The CME was not aimed toward Earth. Nevertheless, this month was very quiet in comparison to the previous one, as only two M-class flares were recorded.
Solar cycle 24