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.
Counter-Streaming Observed in Filament Channel
Credit: IRIS, LMSAL/NASA, P. R. Jibben
This video shows the wealth of information that can be obtained using spectra by utilizing the Doppler effect. The movie shows four panels representing different wavelengths of light near the Magnesium II line. The outer two images are farther away from the center of Mg II and the two middle images represent the left and right "wings" of Mg II. Combined, these four images tell us about the velocities of Mg II plasmas. You'll notice that far from the center of the line, there is not a lot of structure. In the wings of Mg II, you can see a filament. Notice that the left inner panel shows movement from top left to bottom right whereas the inner right image shows the opposite motion. We call this counter-streaming and it is commonly observed in solar filaments. Plasma within a solar filament is not only moving towards and away from us, it is also moving along the channel in opposite directions. This solar filament has a complex velocity pattern that only spectra can reveal.