HR: 14:00h
AN: SH53A-01 INVITED     [Abstracts]
TI: Stochastic Charged Particle Acceleration in the Heliosphere
AU: * Gloeckler, G
EM: gglo@umich.edu
AF: University of Michigan, 2455 Hayward St., Ann Arbor, MI 48109, United States
AU: Fisk, L A
EM: lafisk@umich.edu
AF: University of Michigan, 2455 Hayward St., Ann Arbor, MI 48109, United States
AB: We will describe our work on stochastic acceleration in compressional turbulence, which naturally leads to power law velocity distributions with the unique spectral index of -5 (Fisk and Gloeckler (2006), ApJL 640, L79-L82), and extend it to the acceleration of suprathermal and low-energy (< few MeV) particles at shocks. Redistribution of energy by stochastic acceleration, from the core population consisting of particles with speeds less than V_o (about twice the solar wind speed, V_sw) to the tail particles with speed above V_o, should occur both upstream and downstream from shocks. However, the core particles are heated non- adiabatically when crossing a shock, which raises more of them above the threshold for injection into the tail than is the case in the turbulence upstream of the shock, and this will yield an enhanced suprathermal tail downstream. We derive a simple expression for the pressure jump, as a function of the shock Mach number, of the tail particles in crossing the shock, and compare this with observations of solar wind, suprathermal particles and pickup ions upstream and downstream of shocks observed in the heliosphere with the SWICS instrument on Ulysses.
DE: 2114 Energetic particles (7514)
DE: 2139 Interplanetary shocks
DE: 2152 Pickup ions
DE: 2164 Solar wind plasma
DE: 7845 Particle acceleration
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2007 Joint Assembly