K. Vanninathan, A.M. Veronig, K. Dissauer, M.S. Madjarska, I.G. Hannah and E.P. Kontar

Coronal Response to an EUV Wave from DEM Analysis

Figure 1. First three columns show base-difference images of the evolution of the wave in 3 EUV channels (211 Å, 193 Å, 171 Å) of AIA in which the wave is clearly visible. Fourth column shows the original data from 211 Å channel. Co-temporal images are shown in each row. Time is marked at the bottom of each panel. The two sectors along which the EUV wave was studied are marked as 55 and 210, corresponding to the angles they make with the solar west as measured in the counter-clockwise direction, are shown enclosed by the red dashed lines. The green asterisks along each path marks the fixed ROI which was used to further investigate the plasma properties.


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 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) 171 Å channel is getting heated to higher temperatures corresponding to AIA 193 Å and 211 Å 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 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. We have also identified that heating is taking place at the front of the wave pulse rather than at the rear. Our results provide support for the case that the event under study here is a compressive fast-mode wave or a shock.

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Last Revised: 2015 October 14th