  Post-flare arcades are well-known components of solar flare evolution, which
have been observed for several decades. Coronal rain, cascades of
catastrophically-cooled plasma, outline the loops and provide eye-catching
evidence of the recent flare. These events are acknowledged to be common, but
the scientific literature does not include any statistical overview documenting
just how common the phenomenon actually is. This study reviews Solar Dynamics
Observatory Atmospheric Imaging Assembly (SDO AIA) observations of 241 flares
collected from the Space Weather Prediction Center (SWPC) database between 2011
and 2018. The flares cover the entire strength range of the C, M, and X GOES
classes, and are distributed evenly across the SDO-observed majority of Solar
Cycle 24. We find that post-flare arcade rain occurs for nearly all X and most
M-class flares, but that it tapers off rapidly within C-class flares. There
appears to be a cut-off point around C5, below which the occurrence of
post-flare arcade rain drops significantly. There is also a general positive
correlation between GOES class and the average duration of post-flare rain
events. Post-flare arcade rain events in C-class flares appear to track with
the sunspot number, providing a potential new tool for estimating, if not
predicting, solar cycle strength. Furthermore, condensations appear to be
suppressed in the shortest-length arcade loops of any class observed,
suggesting that active region heating is height-constrained. These results open
up further avenues for future research, including new methods to estimate
energy deposition and to gain greater insight into steady active region
heating.

Solar and Stellar Astrophysics