Chromospheric Evaporation by Particle Beams in Multi-Dimensional Flare Models

Abstract

Evaporation of chromospheric plasma by particle beams has been a standard feature of models of solar flares for many decades, supported both by observations of strong hard X-ray bremsstrahlung signals, and detailed 1D hydrodynamic radiative transfer models with near-relativistic electron beams included. However, in multi-dimensional models, evaporation, if included, has only been driven by heat conduction and by the impact and reflection of fast plasma outflows on the lower atmosphere. Here we present the first multi-dimensional flare simulation featuring evaporation driven by energetic electrons. We use a recent magnetohydrodynamic model that includes beam physics, but decrease the initial anomalous resistivity to create a gentler precursor phase, and improve on the dynamic resistivity treatment that determines where beams are injected. Beam-driven evaporation is achieved. The relevant factors are thermal conduction and electron beams, with the beam electrons more than doubling the kinetic energy flux, and adding 50% to the upward mass from the chromosphere. These findings finally pave the way for integrating detailed 1D flare modelling within a self-consistent 2D and 3D context. The beam fluxes from these self-consistent models can be used to directly compare multi-dimensional results with those from the externally injected beam fluxes of 1D models, as well as understand further evaporation-driven phenomena relating to beams of particles.