Physics
Scientific paper
Dec 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agufmsh42a0769r&link_type=abstract
American Geophysical Union, Fall Meeting 2001, abstract #SH42A-0769
Physics
7513 Coronal Mass Ejections, 7514 Energetic Particles (2114), 7519 Flares, 7534 Radio Emissions
Scientific paper
Almost 80 impulsive near-relativistic (38-315 keV) solar electron events with beam-like pitch-angle distributions were observed by the EPAM experiment between the launch of ACE and the beginning of 2001. The coronal injection times of these electron beams are delayed a median of ~10 minutes after the associated solar electromagnetic emissions, particularly decametric type III radio bursts [Haggerty, Roelof, and Kaiser, Proceedings PRE-V (Graz, Austria), 2001]. Exactly 52 of these electron beams occurred while the SOHO/LASCO coronographs were observing CMEs between 2.6 and 30 Rs. Simnett, Roelof and Haggerty [this Conference] report a close association between the impulsive electron beams and western hemisphere CMEs, jets, etc. They find that the electron injections are delayed after the CME launches, with the electron release occurring when the CME has reached an altitude of 1-2 Rs above the CME launch altitude. The purpose of this poster is to further describe the characteristics of these CME-associated electron beams. Despite their strong associations with solar EM emission and mass ejections, they show a remarkable variety of time histories. These range from "spikes" that have symmetrical Gaussian profiles with FWHM<10 min, through "pulses" that have fast rises and slower decays with FWHM ~30 min, to "ramps" that have gradual rises to plateaus lasting >1 hr (all having velocity-dispersed beam-like pitch-angle anisotropies throughout these periods). There is a remarkable lack of CME-associated spike events prior to mid-1999, suggesting a solar cycle dependence. Because these electron beam events are closely associated with Hα flares centered on W70 heliolongitudes, and because they exhibit strong anisotropies and velocity dispersion in their onsets (i.e., scatterfree propagation over paths ~1.2AU), we cannot ascribe the variety in their time histories to vagaries of interplanetary propagation. Rather, we are led to consideration of variations in the conditions of their coronal acceleration and release.
Haggerty Dennis K.
Roelof Edmond C.
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