Reverse Current in Solar Flares,
STANFORD UNIV CALIF INST FOR PLASMA RESEARCH
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An idealized steady state model of a stream of energetic electrons neutralized by a reverse current in the pre-flare solar plasma is developed. These calculations indicate that, in some cases, a significant fraction of the beam energy may be dissipated by the reverse current. Joule heating by the reverse current is a more effective mechanism for heating the plasma than collisional losses from the energetic electrons because the Ohmic losses are caused by thermal electrons in the reverse current which have much shorter mean free paths than the energetic electrons. Analysis of the steady state model indicates that it can not adequately describe the interaction of the beam with the solar plasma because the atmosphere is rapidly heated. If the time scale for this heating is short enough, the density of the atmosphere can be taken constant in time. The charge separation required to drive the reverse current is expected to respond to changes on a time scale very short compared to the time for the ambient plasma temperature to change significantly, so it is a reasonable approximation to use the steady state results for the electric field. With these simplifications, the heating due to reverse currents is calculated for two injected energetic electron fluxes.