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

Abstract

We report high resolution observations from the SDO/AIA of intensity\noscillations in a hot, T~8-10 MK, loop. The AIA images show a large coronal\nloop that was rapidly heated following plasma ejection from one of the loop's\nfootpoints. A wave-like intensity enhancement, seen very clearly in the 131 and\n94 \\AA\\ channel images, propagated ahead of the ejecta along the loop, and was\nreflected at the opposite footpoint. The wave reflected four times before\nfading. It was only seen in the hot, 131 and 94 \\AA\\ channels. The\ncharacteristic period and the decay time of the oscillation was $\\sim$630 and\n$\\sim$440 s, respectively. The phase speed was about 460-510 km/s which roughly\nmatches the sound speed of the loop (430-480 km/s). The observed properties of\nthe oscillation are consistent with the observations of Doppler shift\noscillations discovered by the SOHO/SUMER and with their interpretation as slow\nmagnetoacoustic waves. We suggest that the impulsive injection of plasma,\nfollowing reconnection at one of the loop footpoints, led to rapid heating and\nthe propagation of a longitudinal compressive wave along the loop. The wave\nbounces back and forth a couple of times before fading.\n