Volume 585, January 2016
|Number of page(s)||7|
|Published online||06 January 2016|
The injection of ten electron/3He-rich SEP events
Institute of Space Physics and Applied Technology,
Beijing, PR China
2 Space Sciences Laboratory, University of California, Berkeley, CA 94720, USA
3 Institute of 4D Technologies, University of Applied Sciences Northwestern Switzerland, 5210 Windisch, Switzerland
4 Applied Physics Laboratory, Johns Hopkins University, Laurel, MD 20723, USA
5 Department of Space Science and CSPAR, University of Alabama in Huntsville, Huntsville, AL 35899, USA
Received: 29 August 2015
Accepted: 2 November 2015
We have derived the particle injections at the Sun for ten good electron/3He-rich solar energetic particle (SEP) events, using a 1.2 AU particle path length (suggested by analysis of the velocity dispersion). The inferred solar injections of high-energy (~10 to 300 keV) electrons and of ~MeV/nucleon ions (carbon and heavier) start with a delay of 17 ± 3 min and 75 ± 14 min, respectively, after the injection of low-energy (~0.4 to 9 keV) electrons. The injection duration (averaged over energy) ranges from ~200 to 550 min for ions, from ~90 to 160 min for low-energy electrons, and from ~10 to 30 min for high-energy electrons. Most of the selected events have no reported Hα flares or GOES SXR bursts, but all have type III radio bursts that typically start after the onset of a low-energy electron injection. All nine events with SOHO/LASCO coverage have a relatively fast (>570 km s-1), mostly narrow (≲30°), west-limb coronal mass ejection (CME) that launches near the start of the low-energy electron injection, and reaches an average altitude of ~1.0 and 4.7 RS, respectively, at the start of the high-energy electron injection and of the ion injection. The electron energy spectra show a continuous power law extending across the transition from low to high energies, suggesting that the low-energy electron injection may provide seed electrons for the delayed high-energy electron acceleration. The delayed ion injections and high ionization states may suggest an ion acceleration along the lower altitude flanks, rather than at the nose of the CMEs.
Key words: Sun: coronal mass ejections / Sun: particle emission / Sun: radio radiation / Sun: flares
© ESO, 2016
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