IRIS Movie of the Day
At least once a week a movie of the Sun taken by NASA's Interface Region Imaging Spectrograph (IRIS) is posted by one of the scientists operating the instrument.
X8 (super)flare and Supra-Arcade Downflows (SADs) - AKA Coronal Tadpoles
Credit: IRIS, LMSAL/NASA, Wei Liu
Supra-arcade downflows (SADs) are sunward-traveling plasma structures that are sometimes observed in the Sun's outer atmosphere, or corona, during solar flares (adopted from
https://en.wikipedia.org/wiki/Supra-arcade_downflows). These enigmatic plasma structures often appear like dark-colored "tadpoles swimming" downward in a bright fan region above an arcade of post-flare loops in the corona. The physical nature of such structures remain elusive. Detecting them with a slit spectrometer would help in great deal elucidating this puzzle, but has proven to be very difficult. On September 10, 2017, an enormous and spectacular solar flare occurred in active region AR 12673 at the southwest solar limb and was classified as X8.2, according to its soft X-ray flux seen by NOAA's GOES satellite, the second largest of this solar cycle (No. 24). Pointing at the right location near the main flare (in the upper left corner of this movie), IRIS observed the arcade, the bright fuzzy fan above it, and many dark tadpoles (SADs) within the fan. This marked the first ever detection of SADs by IRIS since its launch in June 2013. Science analysis is underway to shed light on the nature of these elusive tadpoles.