SOLAR DYNAMICS OBSERVATORY/ATMOSPHERIC IMAGING ASSEMBLY OBSERVATIONS OF A REFLECTING LONGITUDINAL WAVE IN A CORONAL LOOP

We report high resolution observations from the Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) of intensity oscillations in a hot, T similar to 8-10 MK, loop. The AIA images show a large coronal loop that was rapidly heated following plasma ejection from one of the loop's footpoints. A wave-like intensity enhancement, seen very clearly in the 131 and 94 angstrom channel images, propagated ahead of the ejecta along the loop, and was reflected at the opposite footpoint. The wave reflected four times before fading. It was only seen in the hot, 131 and 94 angstrom channels. The characteristic period and the decay time of the oscillation were similar to 630 and similar to 440 s, respectively. The phase speed was about 460-510 km s(-1) which roughly matches the sound speed of the loop (430-480 km s(-1)). The observed properties of the oscillation are consistent with the observations of Dopper-shift oscillations discovered by the Solar and Heliospheric Observatory/Solar Ultraviolet Measurement of Emitted Radiation and with their interpretation as slow magnetoacoustic waves. We suggest that the impulsive injection of plasma, following reconnection at one of the loop footpoints, led to rapid heating and the propagation of a longitudinal compressive wave along the loop. The wave bounces back and forth a couple of times before fading.