34th Solar Physics Division Meeting, June 2003
Session 15 Flares and Microflares I
Oral, Wednesday, June 18, 2003, 1:30-3:30pm, Auditorium

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[15.02] Three Distinct Populations of Solar Energetic Electrons: Flare, Beam, and Type-III

E. C. Roelof, D. K. Haggerty (Johns Hopkins University/Applied Physics Laboratory), G. M. Simnett (University of Birmingham, School of Physics and Astronomy)

Our recent analyses (ApJ., 579, 841-853 and 854-862, 2002) of near-relativistic electrons observed by the EPAM experiment on ACE and the associated solar electromagnetic (EM) emissions and launches of coronal mass ejections (CMEs) indicate that there are three distinct populations of energetic electrons accelerated at the Sun: (I) relativistic electrons that generate associated bursts of microwaves and hard x-rays in the chromosphere and low corona (flares); (II) near-relativistic electrons whose impulsive beam-like onsets at 1AU reveal that they are injected into the solar wind with a delay ~10 min after the EM and prompt meter-wave type-III emissions; and (III) low energy (a few keV) electrons that generate the prompt meter-decameter fast-drift type-III bursts as they escape the corona. The ~10 min injection delay of Population II electrons after the microwave bursts and the start of the dominant meter-wave type-III radio emission implies that Population II is neither a lower-energy component of Population I nor a higher-energy component of Population III. We established that the electron energy corresponding to the exciter speed of the associated meter and decameter type-III bursts is only a few keV. We also established that Population II electrons are injected into the solar wind when the associated CME has reached a distance ~1-3 solar radii above the photosphere. We concluded that a likely acceleration mechanism for Population II was the coronal shock(s) driven by the outgoing CME, and that Population II is therefore related neither to Population I (which does not escape promptly) nor to Population III (which does). We have expanded our original set of 79 beam events (1997-2000) to include 62 more events that ACE/EPAM observed in 2001-2003. The new set of 141 events confirms the delay ~10 min after the EM and prompt meter-wave type-III emissions of the Population II electrons.


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The author(s) of this abstract have provided an email address for comments about the abstract: dennis.haggerty@jhuapl.edu

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