Abstract

In many astrophysical systems mixing between cool and hot temperature gas/plasma through Kelvin-Helmholtz-instability-driven turbulence leads to the formation of an intermediate temperature phase with increased radiative losses that drive efficient cooling. The solar atmosphere is a potential site for this process to occur with interaction between either prominence or spicule material and coronal material allowing the development of intermediate temperature material with enhanced radiative losses. In this talk, I will present a set of equations to model the evolution of such a mixing layer based on the self-similar evolution of a turbulent layer and use this to make predictions for the mixing-driven cooling rate and the rate at which mixing can lead to the condensation of coronal material. These theoretical predictions are benchmarked against 2.5D MHD simulations. Applying the theoretical model to prominence threads or fading spicules we found that the mixing would lead to the creation of transition region material with a cooling time of ∼100s, explaining the warm emission observed as prominence threads or spicules fade in cool spectral lines without the requirement for any heating. In fact, our results imply that the observations of the solar atmosphere that appear to show cool prominence or spicule material becoming warm are likely to be a sign of cooling of the corona and not heating.