Publication Date:
2017-07-12
Description:
We studied three solar energetic particle (SEP) events observed on August 14, 2010, November 03, 2011, and March 05, 2013 by STEREO A, B and near-Earth (L1) spacecraft with a longitudinal distribution of particles 〉 90 degree. Using a forward-modeling method combined with extreme ultraviolet and white-light images we determined the angular extent of the shock, the time and location (cobpoint) of the shock intersection with the magnetic field line connecting to each spacecraft, and compute the shock speed at the cobpoint of each spacecraft. We then examine whether the observations of SEPs at each spacecraft were accelerated and injected by the spatially extended shocks or whether another mechanism such as cross-field transport is required for an alternative explanation. Our analyses results indicate that the SEPs observed at the three spacecraft on November 03, STB and L1 on August 14, and the March 05 SEP event at STA can be explained by the direct shock acceleration. This is consistent with the observed significant anisotropies, short time delays between particle release times and magnetic connection times, and sharp rises in the SEP time profiles. Cross-field diffusion is the likely cause for the August 14 SEP event observed by STA and the March 05 SEPs observed by STB and L1 spacecraft, as particle observations featured weak electron aniotropies and slow rising intensity profiles. Otherwise, the wide longitudinal spread of these SEP increases would require an existence of a circumsolar shock, which may not be a correct assumption in the corona and heliosphere.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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