The Pitch-Angle Distribution Width Between 100 eV to 30 keV During Solar Electron Bursts

In a recent study, we examined the energy dependence of the pitch-angle distribution width between 73-- 1370 eV during solar electron bursts observed by ACE/SWEPAM in 2002. In general, we found that the pitch- angle distribution width during a burst increased with energy from an average of 30° at 73 eV to 55° at 1370 eV. In some events the maximum width at 1370 eV exceeded 80°. Previously published observations at higher energies suggest that burst electron distributions are 30--40° wide at energies above 15 keV, but are narrower, <15°, at energies from 2--10 keV. Combining our recent lower energy observations with these higher energy results suggests that the angular width during a burst is not monotonic with energy, implying a complex electron scattering mechanism. However, to date, no study has considered the pitch-angle distribution width over the energy range from <100 eV to >15 keV during a single solar electron burst. Here we use WIND/3DP data to examine the energy dependence of the pitch- angle distribution width between 100 eV to 30 keV during several solar electron bursts observed in 2002.