Coronal Response to an Euv Wave From Dem Analysis

Abstract

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) 171Å channel is getting heated to higher temperatures corresponding to AIA 193Å and 211Å 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.

The Coronal Analysis of SHocks and Waves (CASHeW) framework

“…Results from previous studies of the density ratios in the low corona (e.g. Veronig et al, 2011;Kozarev et al, 2011;Vanninathan et al, 2015;Kozarev et al, 2015) suggest similar values from DEM and spectrometric calculations À ∼3-20% increase in the density, consistent with the results from this study.…”

Understanding the Physical Nature of Coronal “EIT Waves”

“…(2011) and Vanninathan et al. (2015) have shown that temperature enhancements in EIT waves are due to adiabatic heating, consistent with the wave, field-line stretching, and partially also the current-shell model. This is inconsistent with the continuous-reconnection model that predicts an increase due to non-adiabatic processes ( i.e.…”

“…, 2012; Vanninathan et al. , 2015). This approach (initially driven by the relatively small number of well-observed events in the SOHO/EIT era) led to a situation where the theories proposed to explain EIT waves were primarily developed to explain the behaviour of individual and necessarily different events, while paying minimal attention to predicting more generalised behaviour and observables that may help to understand the true nature of these waves.…”

“…(2011) used the DEM analysis of a limb eruption on 13 June 2011 to find a density increase of 12 %, while Vanninathan et al. (2015) used a similar approach for an on-disk event on 15 February 2011. Using the regularized-inversion technique of Hannah and Kontar (2012, 2013), they found a density increase of 6 – 9 %, corresponding to a temperature increase of during the EIT-wave passage, which was shown to be a result of adiabatic compression at the wave front.…”

On a Small-scale EUV Wave: The Driving Mechanism and the Associated Oscillating Filament

“…For the physical nature of EUV waves, many authors interpreted them as coronal compressive fast-mode magnetosonic waves (e.g., Thompson et al 1998;Patsourakos & Vourlidas 2009;Muhr et al 2010;Veronig et al 2010;Long et al 2011a,b;Xue et al 2013;Vanninathan et al 2015;Yang et al 2013;Long et al 2017), while some peoples believe that EUV waves are not at all waves in physics (e.g., Delannée & Aulanier 1999;Foley et al 2003;Harra & Sterling 2003;Attrill et al 2009;Attrill 2010;Zhukov et al 2009;Dai et al 2010). In most cases, only one bright wavefront can be detected.…”