Spectral Signatures of Transient Heating in the Solar Corona

Hinode/EIS observations of an active region are presented. Intensity and Doppler velocity maps for different emission lines are constructed. Consistent with previous results, the Doppler velocities near the footpoints of coronal loops appear to be blue shifted for emission lines with temperatures above 1 MK. The gradual transition from blue shifts at temperatures above 1 MK to red shifts at temperatures below 1 MK is addressed through numerical modeling of loop dynamics. The simulation results are converted into synthetic EIS observations and compared with the actual measurements. Persistent blue shifts, blue wing enhancements, and red shifts observed in EUV lines are interpreted as a signature of repetitive heating occurring near the loop footpoints on a time scale of several minutes.