Role of Suprathermal Runaway Electrons Returning to the Acceleration Region in Solar Flares

During solar flares, a large flux of energetic electrons propagate from the tops reconnecting magnetic tubes toward lower atmosphere. Over course electrons' transport, co-spatial counter-streaming return current is induced, thereby balancing density. In response to electric field, fraction ambient will be accelerated into runaway regime. However, models describing electron beam/return-current system have generally failed take these suprathermal account self-consistently. We develop model in which an beam drives steady-state, sub-Dreicer return-current locally balances direct and freely accelerates background (return-current) electrons. The self-consistent, i.e., field induced by co-evolution considered. find that (1) can significant number acceleration region, where they further higher energies, few tens percent returning nonthermal beam's (2) energy gain up $10-35$\,keV, (3) heating rate corona reduced order magnitude comparison neglect component. results depend on injected density, temperature density plasma.