Abstract
The dynamics of an electron beam, under the effects of Coulomb collisions and classical Ohmic dissipation of the return current, is analysed for a background plasma with a temperature which is time dependent due to the heating effect of beam dissipation offset by thermal conductive cooling. It is shown that the plasma is heated toward a steady state, in time scales short compared to typical flare beam switch on times, and that in this steady state only two regimes of beam dynamics arise.
For moderate values of the ratio of beam flux to plasma density (F 0/n), beam dynamics is dominated by direct Coulomb collisions as in the usual thick target treatment. With increase of F 0/n, before return current (classical) Ohmic losses can exceed collisions, the return current becomes unstable. In this latter regime beam dynamics is presumably dominated by wave generation and anomalous Ohmic dissipation of the return current, but no detailed treatment is attempted here.
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Brown, J.C., Hayward, J. Dissipation and stability of return currents in solar flares. Sol Phys 80, 129–141 (1982). https://doi.org/10.1007/BF00153428
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DOI: https://doi.org/10.1007/BF00153428