Lower Hybrid Drive in Solar Magnetic Reconnection Regions: Implications for Electron Acceleration and Solar Heating

Lower hybrid (LH) drive involves the resonant acceleration of electrons parallel to the magnetic field B by lower hybrid waves that are driven by ions with ring or ring-beam distributions in perpendicular velocity space. Charge-exchange between hydrogen atoms and protons with relative motions perpendicular to B leads to ring distributions of pickup ions, with concomitant perpedicular ion ``heating''. This paper explores the combination of LH drive and charge-exchange in the outflow regions of magnetic reconnection sites in the solar chromosphere and lower corona, showing that the combined mechanism naturally predicts major perpendicular ion heating and parallel electron acceleration, and exploring the mechanism's relevance to specific solar reconnection phenomena, heating of the solar atmosphere, and production of energetic electrons that generate type III solar radio bursts Although primarily qualitative, analysis shows that the mechanism has numerous attractive aspects, including perpendicular ion heating that increases linearly with ion mass, parallel electron acceleration, predicted ion and electron temperatures that span those of the chromosphere and corona, and parallel electron speeds spanning those for type III bursts. Applications to chromospheric explosive events and low-lying active regions, and to heating the chromosphere, appear particularly suitable. Sweeping of plasma frozen-in to chromospheric and coronal magnetic field lines across the neutral atmosphere due to motions of sub-photospheric fields represents an obvious and important generalization of the mechanism away from reconnection sites. The requirements that the neutrals not be strongly collisionally coupled to the plasma and that sufficient neutrals are available for charge-exchange restricts the LH drive mechanism to above the photosphere but below where the corona is essentially fully ionized. LH drive may thus be important in heating the chromosphere and low corona while other heating mechanisms dominate at higher altitudes.