Prominence Activation by Coronal Fast Mode Shock

TL;DR

This study analyzes a solar flare and associated coronal shock wave, using multi-instrument observations and simulations to understand shock propagation, prominence activation, and plasma compression in the solar corona.

Contribution

It identifies the coronal fast mode shock front through multi-wavelength observations and estimates its Mach number and plasma compression ratio, supported by nonlinear MHD simulations.

Findings

Coronal fast mode shock front identified via EUV and coronagraph images.

Estimated shock Mach number between 1.11 and 1.29.

Plasma compression ratio in prominence between 1.18 and 2.11.

Abstract

An X5.4 class flare occurred in active region (AR) NOAA11429 on 2012 March 7. The flare was associated with very fast coronal mass ejection (CME) with its velocity of over 2500 km/s. In the images taken with STEREO-B/COR1, a dome-like disturbance was seen to detach from expanding CME bubble and propagated further. A Type-II radio burst was also observed at the same time. On the other hand, in EUV images obtained by SDO/AIA, expanding dome-like structure and its foot print propagating to the north were observed. The foot print propagated with its average speed of about 670 km/s and hit a prominence located at the north pole and activated it. While the activation, the prominence was strongly brightened. On the basis of some observational evidence, we concluded that the foot print in AIA images and the ones in COR1 images are the same, that is MHD fast mode shock front. With the help of a linear theory, the fast mode mach number of the coronal shock is estimated to be between 1.11 and 1.29 using the initial velocity of the activated prominence. Also, the plasma compression ratio of the shock is enhanced to be between 1.18 and 2.11 in the prominence material, which we consider to be the reason of the strong brightening of the activated prominence. The applicability of linear theory to the shock problem is tested with nonlinear MHD simulation.