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.
Wavy Sunspot
Credit: IRIS, LMSAL/NASA, Wei Liu (LMSAL/BAERI)
Sunspots are dark areas with strong magnetic fields on the bright surface of the Sun. The importance of sunspots lies in the fact that they are fundamental building blocks of solar active regions that spawn space-weather driving eruptions including flares and coronal mass ejections. This movie, taken by IRIS at 1400 Angstrom on May 25, 2016, shows the leading sunspot in NOAA active region 12546. There are evidently a series of ripple-like features that originate near the sunspot center and travel outward (mainly toward the right-hand side; note a foreshortening effect because of the location of this region near the west limb of the spherical solar surface). These traveling features are so-called running penumbral waves with typical periods in the range of 3-5 minutes. These waves carry important information about energy transfer through different layers of the solar atmosphere as well as the physical nature of sunspots.