On the Stability of Proton Beams against Resonant Scattering by Alfven Waves in Solar Flare Loops
Abstract
The growth of Alfven waves in magnetized hydrogen plasma at flare-loop densities and magnetic field strengths driven by a dilute population of streaming protons in the energy range 10-1000 keV is investigated. The streaming distribution induces wave growth principally through resonant interactions between forward-moving protons and forward-propagating waves. All other factors constant, the maximum growth rate increases with mean beam energy and with increased narrowness of the beam distribution. The frequency of the most rapidly growing waves is inversely related to the mean beam energy. Under typical flare conditions, thermal damping when mean energy equals the Alfven speed effectively stabilizes proton beams of moderate collimation. At beam energies only one order of magnitude larger, thermal damping under flare loop conditions is insufficient to prevent highly restrictive upper limits on the beam-to-background proton density ratio for even mildly collimated proton beams.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 1989
- DOI:
- 10.1086/167617
- Bibcode:
- 1989ApJ...342..576T
- Keywords:
-
- Charged Particles;
- Hydrogen Plasma;
- Magnetohydrodynamic Waves;
- Proton Beams;
- Resonance Scattering;
- Solar Flares;
- Magnetic Fields;
- Particle Interactions;
- Solar Corona;
- Wave Interaction;
- Solar Physics;
- INSTABILITIES;
- PLASMAS;
- SUN: CORONA;
- SUN: FLARES;
- WAVE MOTIONS