coronal rain formation Author: Xiaohong Li
Coronal rain is a widely observed phenomenon where dense and cool condensations form in the hot corona, and then fall down along magnetic loops to the solar surface. The simulations of coronal rain have so far relied on artificially static and localized heating added at the footpoints of the coronal loops. The localized heating adopted in previous simulation work are generally steady and uniform. Since moving magnetic features and turbulent convection are almost ubiquitous in the solar lower atmosphere, the quasi-constant heating profiles are too simplistic for the coronal rain simulation. Coronal heating should be an impulsive phenomenon, affected by multiscale and continuous disturbances in the solar photosphere. Here we present a 2.5D simulation adopting turbulent localized heating, which is randomly distributed both spatially and temporally, to inveatigate the formation of coronal rain in more realistic situations.
We perform the simulation in initially linear force-free magnetic fields that host chromospheric, transition-region, and coronal plasma, with turbulent heating localized on their footpoints. The following movies demonstrate the evolution of number density and temperature. Due to thermal instability, condensations start to occur at the loop top, and rebound shocks are generated by the siphon inflows. Condensations fragment into smaller blobs moving downwards, and as they hit the lower atmosphere, concurrent upflows are triggered. More details about the formation process and the evolution of coronal rain can be found here.