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Abstract:
We recently presented coronal condensations, caused by magnetic reconnection (MR) between coronal loops from extreme ultraviolet observations, over the course of one day, on 2012 January 19. In this paper, by investigating the loops over an extended period of time from January 16 to 20, we present a case for repeated coronal condensations caused by repeated MR between them. In these five days, MR between higher-lying open loops and lower-lying closed loops occurs repeatedly, forming magnetic dips in the higher-lying open loops. During the MR process, cooling and condensation of coronal plasma occur repeatedly. Early on January 16, cooling, but not condensation, of coronal plasma happens. Later, condensation appears at the edge of the dips and falls down along the loops as coronal rains. On January 17, a similar condensation happens at the edge of the higher-lying dips and falls down along the loops. However, another condensation appears in the lower-lying dips and rains down across them. From January 18 to 19, multiple condensations mostly occur at the edge of the dips and fall down both along the loops and across the dips. On January 20, five condensations sequentially appear and rain down across the dips. Overall, 15 condensation events occur in five days, lasting from 0.5 to 15.6 hr. We suggest that the formation of coronal condensations by MR between loops is common in the solar corona. The repeated MR between loops thus plays an essential role in the mass cycle of coronal plasma by initiating repeated catastrophic cooling and condensation.
