Estimate of Plasma Temperatures Across a CME-Driven Shock from a Comparison Between EUV and Radio Data

Abstract

In this work, we analyze the evolution of an EUV wave front associated with a solar eruption that occurred on 30 October 2014, with the aim of investigating, through differential emission measure (DEM) analysis, the physical properties of the plasma compressed and heated by the accompanying shock wave. The EUV wave was observed by the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) and was accompanied by the detection of a metric Type II burst observed by ground-based radio spectrographs. The EUV signature of the shock wave was also detected in two of the AIA channels centered at 193 Å and 211 Å as an EUV intensity enhancement propagating ahead of the associated CME. The density compression ratio X of the shock as inferred from the analysis of the EUV data is X approx 1.23, in agreement with independent estimates obtained from the analysis of the Type II band-splitting of the radio data and inferred by adopting the upstream–downstream interpretation. By applying the Rankine–Hugoniot jump conditions under the hypothesis of a perpendicular shock, we also estimate the temperature ratio as T_{mathrm{D}}/T_{mathrm{U}} approx 1.55 and the post-shock temperature as T_{mathrm{D}}approx 2.75 MK. The modest compression ratio and temperature jump derived from the EUV analysis at the shock passage are typical of weak coronal shocks.