Effects of Flux Tube Geometry on Chromospheric Evaporation Driven by Thermal Conduction


Advisor: Sean Brannon

Solar flares are triggered by reconnection of magnetic field lines in the corona. The newly reconnected flux tubes release free magnetic energy by supersonically contracting toward the solar surface, which compresses and heats the confined plasma at the loop top, resulting in well-known reconnection shocks. Steep temperature gradients across the propagating shocks create fast-moving thermal conduction fronts, which deposit thermal energy in the chromosphere and drive upflows of plasma referred to as chromospheric evaporation. The upflow characteristics will depend, to some extent, on the cross-sectional geometry of the flux tube, especially in the transition region. Strong constriction, as might occur at the center of a network element, will reduce the energy flux, and possibly reduce the evaporation. On the other hand, an expanding nozzle will accelerate supersonic evaporation which is driven though it.

In this project we are developing an understanding of hydrodynamic theory, coronal loop atmospheres, and reconnection shocks. We work with a one-dimensional hydrodynamic code, which simulates evaporative upflows driven by shock-initiated thermal conduction fronts, to explore a defined parameter space of flux tube geometries and the resulting upflow characteristics.