Coronal response to an EUV wave from DEM analysis
Kamalam Vanninathan
University of Graz
A.Veronig (University of Graz), K.Dissauer (Universiy of Graz), M.Madjarska (Armagh Observatory), I.Hannah (University of Glasgow), E.Kontar (University of Glasgow)
EUV (Extreme-Ultraviolet) waves are globally propagating disturbances that
have been observed since the era of the SoHO/EIT instrument. Although the
kinematics of the wave front and secondary wave components have been widely
studied, there is not much known about the generation and plasma properties of
the wave. In this paper we discuss the effect of an EUV wave on the local plasma
as it passes through the corona. We studied the EUV wave, generated during the
2011 February 15 X-class flare/CME event, using Differential Emission Measure
(DEM) diagnostics. We analyzed regions on the path of the EUV wave and investigated the local density and temperature changes. From our study we have
quantitatively confirmed previous results that during wave passage the plasma
visible in the Atmospheric Imaging Assembly (AIA) 171A channel is getting
heated to higher temperatures corresponding to AIA 193A and 211A channels.
We have calculated an increase of 6 - 9% in density and 5 - 6% in temperature
during the passage of the EUV wave. We have compared the variation in temperature with the adiabatic relationship and for the first time have quantitatively demonstrated the phenomenon of heating due to adiabatic compression at the wave front. However, the cooling phase does not follow adiabatic relaxation but shows slow decay indicating slow energy release being triggered by the wave passage. Our results provide support for the case that the event under study here is a compressive fast-mode wave or a shock.