| ACE News Archives | ACE News #64 - July 10, 2002 |
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| ACE Science Nuggets |
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ACE Science Nuggets |
A comprehensive study of Impulsive, beam-like, scatter-free electron events observed by the ACE/EPAM instrument finds that these near-relativistic electron events are well associated with coronal mass ejections (CMEs) observed by SOHO/LASCO off the west limb of the Sun. The electron injection time at the Sun may be determined by subtracting the transit time along the spiral field line (1.2 AU for 0° pitch-angle) from the observed onset time at 1 AU, as illustrated above. A fit of CME height vs. time using LASCO images gives the radial distance of the CME at the time of electron injection. The result (see above) is that near-relativistic electrons are injected onto interplanetary magnetic field lines when the associated CME is at ~1-4 solar radii. Simnett, Roelof and Haggerty (ApJ, in press, 2002) show that the correlations between CME velocity and either electron intensity or spectral shape are consistent with the acceleration of these electrons by CME-driven shocks.
Contributed by Dennis Haggerty and Edmond Roelof of Johns Hopkins University/Applied Physics Laboratory and George Simnett of the University of Birmingham, UK.
Last modified 10 July 2002, by
Andrew Davis