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.
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28 Jun 2017
Following the Light of the Sun
Credit: IRIS, LMSAL/NASA, Jakub Prchlik
Why solar flares produce bright ribbons in the chromosphere (like the above X1.6 flare observed by IRIS) remains uncertain. However, a leading theory predicts magnetic fields near the surface constrain the flare ribbon's shape. The theory assumes magnetic fields rapidly reconfigure during a flare. Due to the changing magnetic field, material streams towards the chromosphere in a thin sheet. Finally, the thin material sheet impacts chromosphere. The impact converts the material's motion into the bright ribbons observed by IRIS during flares.