Post-flare thermal waves in the solar corona

While imaging giant post-flare arches in the solar corona, the Hard X-Ray Spectrometer aboard the SMM detected thermal disturbances propagating through the corona after two-ribbon flares. The speed of propagation is close to, or below, 10 km s^?1, and no obvious time-variation of the speed is indicated in the HXIS data. For subsequent two-ribbon flares in the same active region, these thermal disturbances (waves) exhibit highly homologous properties; thus the waves appear to propagate through preexisting arches formed after earlier flares. Temperatures of > 20 × 10⁶ K have been detected in these moving phenomena. We suggest that we see here in X-rays upper products of the consecutive reconnections which create the post-flare loops below. Temperature maps in fine field of view of HXIS offer now a new possibility to detect postflare arches in the corona built during two-ribbon flares.