Flare Footpoint Regions and a Surge Observed by Hinode/EIS, RHESSI, and SDO/AIA

The Extreme-ultraviolet Imaging Spectrometer (EIS) on the Hinode spacecraft observed flare footpoint regions coincident with a surge for an M3.7 flare observed on 2011 September 25 at N12 E33 in active region 11302. The flare was observed in spectral lines of O vi, Fe x, Fe xii, Fe xiv, Fe xv, Fe xvi, Fe xvii, Fe xxiii, and Fe xxiv. The EIS observations were made coincident with hard X-ray bursts observed by RHESSI. Overlays of the RHESSI images on the EIS raster images at different wavelengths show a spatial coincidence of features in the RHESSI images with the EIS upflow and downflow regions, as well as loop-top or near-loop-top regions. A complex array of phenomena were observed, including multiple evaporation regions and the surge, which was also observed by the Solar Dynamics Observatory/Atmospheric Imaging Assembly telescopes. The slit of the EIS spectrometer covered several flare footpoint regions from which evaporative upflows in Fe xxiii and Fe xxiv lines were observed with Doppler speeds greater than 500 km s^-1. For ions such as Fe xv both evaporative outflows (∼200 km s^-1) and downflows (∼30-50 km s^-1) were observed. Nonthermal motions from 120 to 300 km s^-1 were measured in flare lines. In the surge, Doppler speeds are found from about 0 to over 250 km s^-1 in lines from ions such as Fe xiv. The nonthermal motions could be due to multiple sources slightly Doppler-shifted from each other or turbulence in the evaporating plasma. We estimate the energetics of the hard X-ray burst and obtain a total flare energy in accelerated electrons of ≥7 × 10²⁸ erg. This is a lower limit because only an upper limit can be determined for the low-energy cutoff to the electron spectrum. We find that detailed modeling of this event would require a multithreaded model owing to its complexity.