Xiaohong Li

As part of the ERC PROMINENT project, my work focuses on simulations of condenstions such as coronal rain and prominence using MPI-AMRVAC.

So far, my progress includes:

1. Coroanl rain simulation

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. Adopting the MPI-AMRVAC code, we present a 2.5-dimensional magnetohydrodynamic simulation, which includes thermal conduction and radiative cooling, to investigate the formation and evolution of the coronal rain phenomenon. 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. 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. Larger clumps show us clear coronal rain showers as dark structures in synthetic EUV hot channels and as bright blobs with cool cores in the 304 Å channel, well resembling real observations. Following coronal rain dynamics for more than 10 hr, we carry out a statistical study of all coronal rain blobs to quantify their widths, lengths, areas, velocity distributions, and other properties. The coronal rain shows us continuous heating–condensation cycles, as well as cycles in EUV emissions. Compared to the previous studies adopting steady heating, the rain happens faster and in more erratic cycles. Although most blobs are falling downward, upwardmoving blobs exist at basically every moment. We also track the movement of individual blobs to study their dynamics and the forces driving their movements. The blobs have a prominence-corona transition-region-like structure surrounding them, and their movements are dominated by the pressure evolution in the very dynamic loop system. More details can be found in here.

2. Flux emergence simulation

Flux emergence is responsible for various solar eruptions. Combining observation and simulations, we investigate the influence of flux emergence at one footpoint of an arcade on coronal rain as well as induced eruptions. The emergence changes the pressure in the loops, and the internal coronal rain all moves to the other side. The emerging flux reconnects with the overlying magnetic field, forming a current sheet and magnetic islands. The plasma is ejected outwards and heated, forming a cool jet ∼6000 K and a hot X-ray jet ∼4 million Kelvin (MK) simultaneously. The jet dynamical properties agree very well between observation and simulation. In the simulation, the jet also displays transverse oscillations with a period of 8 minutes, in a so-called whiplike motion. The movement of the jet and dense plasmoids changes the configuration of the local magnetic field, facilitating the occurrence of the Kelvin–Helmholtz instability, and vortex-like structures form at the boundary of the jet. Our simulation clearly demonstrates the effect of emergence on coronal rain, the dynamical details of reconnecting plasmoid chains, the formation of multithermal jets, and the cycling of cool mass between the chromosphere and the corona. The associated paper can be found here.

For my former reasearch, please check my personal webpage and ORCiD. Feel free to contact me: xiaohong.li@kuleuven.be.