Interaction of EIT Waves with Coronal Active Regions

Abstract

Large-scale coronal waves associated with flares were first observed by the Solar and Heliospheric Observatory (SOHO) Extreme ultraviolet Imaging Telescope (EIT). We present the first three-dimensional MHD modeling of the interaction of the EIT waves with active regions and the possibility of destabilization of an active region by these waves. The active region is modeled by an initially force-free, bipolar magnetic configuration with gravitationally stratified density. We include finite thermal pressure and resistive dissipation in our model. The EIT wave is launched at the boundary of the region, as a short time velocity pulse that travels with the local fast magnetosonic speed toward the active region. We find that the EIT wave undergoes strong reflection and refraction, in agreement with observations, and induces transient currents in the active region. The resulting Lorentz force leads to the dynamic distortion of the magnetic field and to the generation of secondary waves. The resulting magnetic compression of the plasma induces flows, which are particularly strong in the current-carrying active region. We investigate the effect of the magnetic field configuration and find that the current-carrying active region is destabilized by the impact of the wave. Analysis of the threedimensional interaction between EIT waves and active regions can serve as a diagnostic of the active region coronal magnetic structure and stability.

Large-scale Globally Propagating Coronal Waves

“…Conversely, the wave will be refracted towards "valleys" of low fast-mode speeds. This behavior was well reproduced by simulations based on geometric acoustics (Uchida, 1968;Uchida et al, 1973;Afanasyev and Uralov, 2011) and 3D MHD simulations (Wang, 2000;Ofman and Thompson, 2002;Terradas and Ofman, 2004). This refracting behavior of coronal waves can now be directly seen with AIA (e.g., Shen et al, 2013).…”

“…This was seen at AR boundaries in MHD simulations by Ofman and Thompson (2002), and has been proposed to explain prolonged localized brightenings in Hα and He i (Vršnak et al, 2002b;Warmuth et al, 2004b). The notion of localized energy release triggered by a passing wave was also invoked to explain a temporary emission increase of a broad-band metric radio source associated with a coronal waves .…”

SDO/AIA and Hinode/EIS observations of interaction between an EUV wave and active region loops

“…This is the first time that a secondary wave produced by a reflected wave is observed. It is consistent with secondary waves produced by distorted AR magnetic fields, which were simulated by Ofman & Thompson (2002). Recently, Li et al (2012) studied a global EUV wave on 2011 June 7.…”

“…However, instead of disappearing after the secondary wave was generated, the reflected wave continuously propagated forward. These are consistent with secondary waves produced by distorted AR magnetic fields, which were simulated by Ofman & Thompson (2002). At 04:30:24 UT, another reflected wave (marked by "RW2" in Figures 6(c)-(e)) appeared above the solar limb at a velocity of 400±10 km s −1 .…”

“…They found that part of the EUV wave transmitted through the CH, and the loop arcade at the CH boundary triggered a secondary wave, which appeared to have been reflected. Secondary waves produced by distorted AR magnetic field have been simulated by Ofman & Thompson (2002), and then observationally confirmed by Li et al (2012). Additionally, EUV waves were reported to interact with coronal loops (Thompson et al 1998;Delannée & Aulanier 1999;Delannée 2000).…”