Angular Width of Electron Flux Peaks during a Wave-Particle Interaction Event
Tuesday, 16 December 2014
A sequence of quasiperiodic peaks in the 17-26 keV electron pitch angle distributions were observed during a 30-minute interval by the MagEIS instrument on the Van Allen Probes. These electron features were correlated with simultaneously detected emissions of whistler-mode chorus waves [Fennell et al., GRL, 2014]. The apparent width of the peaks in pitch angle was approximately 10° (FWHM), which is comparable to the 10° x 20° field-of-view of the MagEIS sensor. We report the results of a deconvolution procedure to estimate the true angular width of these peaks. MagEIS was in high rate mode during this period so that flux samples were accumulated every ~10 ms, corresponding to an angular cadence of every 0.36°. A maximum entropy method is used to deconvolve the observed distributions and the instrument response function. This technique provides the smoothest possible distribution that is consistent with the data and their statistical properties. The results of this analysis show that the peaks are significantly more narrow than previously reported. We discuss the implications of this narrow angular width for wave-particle interactions.