Determining heating rates in reconnection formed flare loops

Abstract

In this work, we determine heating rates in reconnection formed are loops with analysis of observations and models. We utilize the spatially resolved ultraviolet (UV) light curves and the thick-target hard X-ray (HXR) emission to construct heating rates of a few thousand are loops anchored at the UV footpoints. These loops are formed and heated by magnetic reconnection taking place successively. These heating rates are then used as an energy input in the zero-dimensional Enthalpy-Based Thermal Evolution of Loops (EBTEL) model to calculate the evolution of plasmas in these loops and compute synthetic spectra and light curves in Soft X-ray (SXR) and extreme ultraviolet (EUV), which compare favorably with those observed by the Geostationary Operational Environmental Satellite (GOES), Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), and Solar Dynamics Observatory (SDO). With a steady-state assumption, we also compute the transition-region differential emission measure (DEM) at the base of each are loop during its decay phase, and compare the predicted UV and EUV emissions at the footpoints with AIA observations. This study presents a method to constrain heating of reconnection-formed are loops using all available observations, and provides insight into the physics of energy release and plasma heating during the are. Furthermore, using RHESSI HXR observations, we could also infer the fraction of non-thermal beam heating in the total heating rate of are loops. For an M8.0 are on 2005 May 13, the lower limit of the total energy used to heat the are loops is estimated to be 1.22 x 10 31 ergs, out of which, less than 20% is carried by beam-driven upflows during the impulsive phase. The method is also applied to analyzing an eruptive M3.7 are on 2011 March 7 and a compact C3.9 are on 2012 June 17. Both flares are observed in EUV wavelengths by the Atmospheric Imaging Assembly (AIA) and Extreme Ultraviolet Variability Experiment (EVE) onboard the SDO, which allow us to investigate the are evolution from the heating to cooling phase. The results show that the model-computed synthetic EUV emissions agree very well with those observed in AIA bands or EVE lines, indicating that the method successfully captures heating events and appropriately describes mean properties of are plasma shortly after the heating phase.