The Electron Energy Spectrum from Large Solar Flares |
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| Authors: | G M Simnett |
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| Institution: | (1) School of Physics and Astronomy, University of Birmingham, B15 2TT, U.K. |
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| Abstract: | We report on the differential electron spectrum for intense transient events seen at one AU by the EPAM instrument on the
Advanced Composition Explorer (ACE) spacecraft. Over an observing period from September 1997 to September 2005, there were 45 major events that could be
reliably identified with a source flare on the Sun. In the ∼40 – 300 keV energy range, the electron spectral index was between
one and three for all but two of the events. Twenty-five of the events were associated with Geostationary Operational Environmental
Satellites (GOES) X-ray class X flares. We compare this result with the spectral index measured from electron pulse events,
lasting approx. one hour or less, where the spectral index is typically much softer than three. This suggests that the measured
spectral index of near-relativistic electrons at one AU may be a reliable indicator of the source. We also examine the likelihood
that fast coronal mass ejections (CMEs) are responsible in themselves for accelerating near-relativistic electrons and conclude
that they do not. |
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