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.
Hidden Wisps of Smoke
Credit: IRIS, LMSAL/NASA, Chad Madsen, SAO
This video is bit unusual compared to the others typically featured here. Instead of a video in two spatial dimensions, this video features distance along the slit on the vertical axis and time elapsed in the horizontal axis. By playing the video, you aren't progressing in time but rather wavelength in the near ultraviolet. As wavelength progresses, we begin to cross one of two emission lines from singly ionized magnesium. Prior to reaching the first line (known as the "Mg II k" line,) the scene is unremarkable, only featuring some bright and dark horizontal streaks from the background environment. However, upon reaching the first peak of Mg II k, several dark wispy strands arise seemingly out of nowhere streaking diagonally across the field of view. These are the remnants of a cool filament suspended over the hotter background plasma that has erupted and been torn apart. As we move to the second peak of Mg II k, the dark strands shift from the lower half of the field of view to the upper half. This actually gives us a clue as to how these strands are moving. Features appearing near the first peak of Mg II k are "blueshifted", indicating that they are moving towards us while features appearing near the second peak are "redshifted", indicating that they are moving away from us. So, these torn apart filament strands seem to be rotating along an axis like spokes on a wheel with the lower portion moving away from the Sun and the upper half moving back towards it.