Energy time dispersion of a new class of magnetospheric ion events observed near the Earth’s bow shock
We have analyzed high time resolution (≥6 s) data during the onset and the decay phase of several energetic (≥35 keV) ion events observed near the Earth’s bow shock by the CCE/AMPTE and IMP-7/8 spacecraft, during times of intense substorm/geomagnetic activity. We found that forward energy dispersion at the onset of events (earlier increase of middle energy ions) and/or a delayed fall of the middle energy ion fluxes at the end of events are often evident in high time resolution data. The energy spectra at the onset and the decay of this kind of events show a characteristic hump at middle (50–120 keV) energies and the angular distributions display either anisotropic or broad forms. The time scale of energy dispersion in the ion events examined was found to range from several seconds to ∼1 h depending on the ion energies compared and on the rate of variation of the Interplanetary Magnetic Field (IMF) direction. Several canditate processes are discussed to explain the observations and it is suggested that a rigidity dependent transport process of magnetospheric particles within the magnetosheath is most probably responsible for the detection of this new type of near bow shock magnetospheric ion events. The new class of ion events was observed within both the magnetosheath and the upstream region.
On the origin of the forward velocity dispersion of ion events observed near the Earth's and Jupiter's bow shock
We examined a great number of ion events observed in the vicinity of the Earth's (CCE/AMPTE, IMP-6,7, and 8) and Jupiter's (Voyager-2, Ulysses) bow shock, which showed during their onset(decay) phase earlier(later) flux increases (decreases) at higher than at lower energies, i.e. presented forward velocity dispersion(FVD). The comparison of the whole set of observations with several theoretical frameworks (shock acceleration, E×B drift, propagation -temporal process, magnetosheath scattering) suggests that a rigidity dependent leakage process of magnetospheric ions (due to wave scattering) in the magnetosheath is most probably the main agent for the appearance of FVD of energetic (E≥30keV) ions upstream and downstream from the Earth's and Jupiter's bow shock.
Radiation exposure reduction by use of Kevlar cassettes in the neonatal nursery.
A study was performed to determine whether the use of Kevlar cassettes in the neonatal intensive care nursery would reduce radiation exposure to patients. The radiation dose to the neonates was measured by using thermoluminescent dosimeters. In addition, the attenuation of the Kevlar cassettes and the sensitivity of the film-screen combination were compared with the previously used system. The greatest radiation reduction using a mobile X-ray unit was 27%; based on sensitivity measurements, the theoretical reduction averaged 38%. The reduction in radiation exposure resulted from reduced attenuation by the Kevlar cassette.