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Title: Radio Spectroscopic Imaging of a Solar Flare Termination Shock: Split-band Feature as Evidence for Shock Compression
Award ID(s):
1654382 1735405 1723436 1723313 1735525 1735414
PAR ID:
10129172
Author(s) / Creator(s):
; ; ; ;
Date Published:
Journal Name:
The Astrophysical Journal
Volume:
884
Issue:
1
ISSN:
1538-4357
Page Range / eLocation ID:
63
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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  1. null (Ed.)
  2. We have performed two-dimensional hybrid simulations of non-relativistic collisionless shocks in the presence of pre-existing energetic particles (‘seeds’); such a study applies, for instance, to the re-acceleration of galactic cosmic rays (CRs) in supernova remnant (SNR) shocks and solar wind energetic particles in heliospheric shocks. Energetic particles can be effectively reflected and accelerated regardless of shock inclination via a process that we call diffusive shock re-acceleration. We find that re-accelerated seeds can drive the streaming instability in the shock upstream and produce effective magnetic field amplification. This can eventually trigger the injection of thermal protons even at oblique shocks that ordinarily cannot inject thermal particles. We characterize the current in reflected seeds, finding that it tends to a universal value $$J\simeq en_{\text{CR}}v_{\text{sh}}$$ , where $$en_{\text{CR}}$$ is the seed charge density and $$v_{\text{sh}}$$ is the shock velocity. When applying our results to SNRs, we find that the re-acceleration of galactic CRs can excite the Bell instability to nonlinear levels in less than $${\sim}10~\text{yr}$$ , thereby providing a minimum level of magnetic field amplification for any SNR shock. Finally, we discuss the relevance of diffusive shock re-acceleration also for other environments, such as heliospheric shocks, galactic superbubbles and clusters of galaxies. 
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