Spectroscopic study of a limb flare observed by Hinode, SDO, RHESSI, and STEREO

An M1.3 flare was observed on 2014 January 13 around 21:48 UT at the west limb by Hinode, SDO, RHESSI, and STEREO. Since the flare was observed over the limb we were able to investigate the flaring loop structure and properties of the loop such as temperature, abundances, and dynamics, with height. Using the Hinode/EIS Fe XXIV/XXIII temperature sensitive line ratio and the intensity ratio of the AIA channels we found that the temperature increases with height to a value of over 10^7 K at the loop-top. The measured line of sight (Doppler) velocity also shows strong redshifts in the range of 100 - 500 km/s which are faster in the loop-top region. Using the STEREO observations, we have examined the 3D structure of the loop and its tilt angle. The results suggest that the strong redshift in the loop-top region is indicative of upflows along the loop. RHESSI observations show both Hard X-ray (25-50 keV) and Soft X-ray (12-25 keV) emission in footpoint brightenings at the beginning of the flare, which implies the presence of non-thermal emission, or accelerated particles. Ten minutes later, the soft X-ray emission moves to the loop top. The evolution of the temperature, flows, Hard X-ray, and Soft X-ray emission suggests that evaporation flows are responsible for the strong outflows near the loop top. Using the EIS Ca XIV/Ar XIV diagnostic ratio we found that the flaring loop has a coronal abundance (first ionization potential bias >4). This is inconsistent with the abundance signature expected when the flare evaporates photospheric plasma. We will discuss this disagreement and the other observed properties.