Physics – Plasma Physics
Scientific paper
Dec 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufmsh42b..01g&link_type=abstract
American Geophysical Union, Fall Meeting 2010, abstract #SH42B-01
Physics
Plasma Physics
[7513] Solar Physics, Astrophysics, And Astronomy / Coronal Mass Ejections, [7514] Solar Physics, Astrophysics, And Astronomy / Energetic Particles, [7519] Solar Physics, Astrophysics, And Astronomy / Flares, [7845] Space Plasma Physics / Particle Acceleration
Scientific paper
Particles accelerated in Solar Energetic Particle (SEP) events sometimes exhibit large angular extents. The broadest angular spreads observed in large events are commonly interpreted in terms of extended acceleration in a shock source which intercepts interplanetary magnetic field lines often separated by more than 100 degrees in longitude. By way of contrast, during impulsive flare-associated events the small spatial scale of the source typically leads to modest angular spread of energetic particles. In absence of shocks, the longitudinal spread of the particles has been attributed to lateral transport in the interplanetary medium or in the corona (e.g. Wibberenz and Cane, 2006) or to quickly diverging open magnetic field lines above the source active region (e.g. Klein et al., 2008). Such kind of processes could also operate during large gradual events with a significant flare contribution. After an extended solar minimum a significant increase in the SEP activity starting late in 2009 has been observed. During this period, several events were detected simultaneously by the Solar Electron and Proton Telescope (SEPT) onboard the two STEREO spacecraft when their longitudinal separation was more than 120 degrees. We present a survey of multi-spacecraft observations of 55-425 keV electron events during the early phase of solar cycle 24. With the aim of understanding the physical processes responsible for the large angular spread of the particles, we link the multi-point in-situ observations at 1 AU to the associated solar phenomena. We discuss the importance of these phenomena with respect to the particle observations. Pure impulsive events are identified by the lack of shock signatures and enhanced 3He abundances. The good observational coverage provided by the two STEREO together with SOHO and ACE provides the opportunity to compare time profiles, onset times, anisotropies and spectra observed by different spacecraft, and to study their dependences with angular separation (in both longitude and latitude) of the spacecraft footpoints with respect to the source active region.
Cohen M. C.
Dresing Nina
Droege Wolfgang
Gómez-Herrero Raúl
Heber Bernd
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