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Relating the Properties of Chromospheric Condensation to Flare Energy Transported by Thermal Conduction

Chromospheric condensation is a brief episode of downflow often accompanying energy release and evaporation in a solar flare. While this component of a flare reflects the energy release process only indirectly, it can be observed at high spatial and temporal resolution, even from the ground. It appears in spectroscopic observations of cooler lines, formed below ∼105 K, as a redshift that peaks and decays after less than 1 minute. In order to use this signature to infer characteristics of solar flare energy release, it is important to establish quantitative relationships with properties of the condensation. The initial investigation reported here does so after restricting consideration to energy transport via thermal conduction into a simplified, stratified chromosphere. We develop an analytical expression for the decay of a condensation propagating into a stratified atmosphere. This model provides a relationship between shock velocity and preshock density structure. We also use one-dimensional gasdynamic simulations to explore the dynamics of these shocks as they penetrate into the stratified chromosphere. We find that the peak downflow speed primarily reflects the energy flux into the chromosphere, while the product of this velocity and the redshift duration is proportional to the preshock density scale height as H ≃ 0.6u 0 τ.