Physics
Scientific paper
Dec 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufmsh23c..06n&link_type=abstract
American Geophysical Union, Fall Meeting 2008, abstract #SH23C-06
Physics
7514 Energetic Particles (2114), 7845 Particle Acceleration, 7851 Shock Waves (4455), 7867 Wave/Particle Interactions (2483, 6984)
Scientific paper
Solar-energetic-proton (SEP) acceleration at a parallel shock is modeled with self-consistent Alfvén-wave excitation and shock transmission. 18 - 50 keV seed protons at 0.001 plasma proton density are accelerated in 10 minutes to a power-law intensity spectrum rolling over at ~ 300 MeV by a 2500 km/s shock launched from 3.5 solar radii in typical coronal condition with low ambient wave intensity. Scattering of large pitch-angle high-energy SEPs by waves amplified by small pitch-angle low-energy SEPs bootstraps the acceleration. The rapid acceleration is inappreciably retarded by wavenumber shift of shock-transmitted Alfvén waves or by the interaction of sunward streaming SEPs with downstream waves. There is no significant second-order Fermi acceleration. SEP acceleration beyond the 'knee' energy proceeds from large to small pitch-angles, for gyroresonant wave-particle interaction at k ~ B/(μ P). B is magnetic field, k wavenumber, P rigidity and μ pitch-cosine. Classical mean-free-path is inapplicable in this time-dependent process. Using the above μ-dependent resonant condition to calculate wave-growth rates but the 'sharpened' condition k ~ B/P to calculate μ-scattering rates underestimates scattering by self-amplified waves, giving little acceleration (Berezhko et al 1998). Using k ~ B/P to calculate wave-growth and scattering rates (Vainio & Laitinen 2007) is consistent but incorrectly requires the SEPs to amplify unique waves from the weak ambient state. In contrast, true gyroresonant interaction must 'relay' the influence of amplified waves from low-P large-μ SEPs to high-P low-μ SEPs, leading to fast acceleration. Model results will be presented and dependence on model parameters will be discussed.
Ng Chee K.
Reames Donald. V.
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