Other
Scientific paper
Apr 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994apj...425..856l&link_type=abstract
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 425, no. 2, p. 856-860
Other
41
Electron Acceleration, Energy Transfer, Magnetohydrodynamic Turbulence, Solar Flares, Angular Distribution, Energy Absorption, Ion Scattering, Light Curve, Trapped Particles
Scientific paper
We recently proposed that a magnetohydrodynamic (MHD) turbulent cascade produces the bulk energization of electrons to approximately 25 keV in the impulsive phase of solar flares (LaRosa & Moore 1993). In that scenario, (1) the cascading MHD turbulence is fed by shear-unstable Alfvenic outflows from sites of strongly driven reconnection in the low corona, and (2) the electrons are energized by absorbing the energy that flows down through the cascade. We did not specify the physical mechanism by which the cascading energy is ultimately transferred to the electrons. Here we propose that Fermi acceleration is this mechanism, the process by which the electrons are energized and by which the cascading MHD turbulence is dissipated. We point out that in the expected cascade MHD fluctuations of scale 1 km can Fermi-accelerate electrons from 0.1 keV to approximately 25 keV on the subsecond timescales observed in impulsive flares, provided there is sufficient trapping and scattering of electrons in the MHD turbulence. We show that these same fluctuations provide the required trapping; they confine the electrons within the turbulent region until the turbulence eis dissipated. This results in the energization of all of the lectrons in each large-scale (5 x 107cm) turbulent eddy to 25 keV. The Fermi process also requires efficient scattering so that the pitch-angle distribution of the accelerating electrons remains isotropic. We propose that the electrons undergo resonant scattering by high-frequency plasma R-waves that, as suggested by others (Hamilton & Petrosian 1992), are generated by the reconnection. Ions are not scattered by R-waves. Provided that there is negligible generation of ion-scattering plasma turbulence (e.g., L-waves) by the reconnection or the MHD turbulence, the ions will not Fermi-accelerate and the cascading energy is transferred only to the electrons. We conclude that, given this situation, electron Fermi acceleration can plausibly account for the electron bulk energization in impulsive solar flares.
LaRosa Ted N.
Moore Robert L.
Shore Steve N.
No associations
LandOfFree
A new path for the electron bulk energization in solar flares: Fermi acceleration by magnetohydrodynamic turbulence in reconnection outflows does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with A new path for the electron bulk energization in solar flares: Fermi acceleration by magnetohydrodynamic turbulence in reconnection outflows, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A new path for the electron bulk energization in solar flares: Fermi acceleration by magnetohydrodynamic turbulence in reconnection outflows will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1256131