PARTICLE ACCELERATION AT NEAR-PERPENDICULAR SHOCKS: THE ROLE OF FIELD-LINE TOPOLOGY
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721-0092 (United States)
Particle acceleration at two-dimensional (2D) shocks can significantly differ from our expectations based on one-dimensional shocks. We discuss several features of 2D shocks. First, we present a simple example of diffusive acceleration to demonstrate that (1) 'hot spots' and cold regions can be expected along the shock face, as the field-line configuration changes along the shock face, (2) the flux of accelerated particles (even the average flux) can be expected to increase beyond the shock, and (3) 2D structures may lead to a softening of the spectrum. We also address quasi-perpendicular shocks and discuss what happens when a field line is hit by a curved shock or is detaching from a shock. This mechanism is of interest on both large and small scales. We consider pure field-aligned transport and address both the diffusive (large scale) and scatter-free (small scale) cases, looking from the perspective of one field line. We find that quasi-trapping of particles in front of the shock can lead to rapid and effective acceleration via multiple mirroring on the ever faster moving shock. This mechanism may be of importance at various astrophysical, heliospheric, and coronal mass ejection driven shocks.
- OSTI ID:
- 21467194
- Journal Information:
- Astrophysical Journal, Vol. 723, Issue 1; Other Information: DOI: 10.1088/0004-637X/723/1/393; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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