Investigation of supra-arcade downflows with a 3D numerical model of solar flares
Abstract
Supra-arcade downflows are low-emission downflows observed at cusp regions of solar flares. Rayleigh-Taylor-type instabilities have been proposed to as a possible mechanism for the supra-arcade downflows in our previous paper (Guo et al. 2014), in which numerical simulations of a reconnecting current sheet qualitatively reproduce AIA observations of supra-arcade downflows. As a follow-up work of the previous paper, we conduct numerical simulations with more sophisticated setups (Shen et al. 2011) to gain a coherent understanding of three-dimensional fine structures above flare arcades. These fine structures disturb local plasma, cause turbulent flows and possibly help to heat plasma in the cusp region, as suggested by spectroscopic observations of the cusp region (Hanneman & Reeves 2014, Reeves et al. 2017, Innes et al. 2003, McKenzie et al. 2013). In our simulations, we observe high-speed Doppler flows in the supra-arcade fan, which lead to Doppler-shifted components in synthetic line profiles of hot flare lines. We also find that the instabilities that drive supra-arcade downflows could cause non-thermal broadenings of line profiles as a consequence of turbulent flows. We compare our simulations with existing observations and discuss the possible impacts of supra-arcade downflows on flare energetics. Last but not least, we conducted parameter scans regarding to certain plasma parameters (e.g. beta and guide field) and study conditions under which supra-arcade downflows occur.
- Publication:
-
Solar Heliospheric and INterplanetary Environment (SHINE 2018)
- Pub Date:
- July 2018
- Bibcode:
- 2018shin.confE.191G