Chromospheric filaments
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Newly emerging active region
IRIS
Active region filaments in NOAA AR 11850, as observed on 2013 September 23 by the IRIS spectrograph.
This spectroheliogram shows a newly emerging active region in the core of the chromospheric Mg II k 2796 Å line, which is regularly observed from space with NASA's Interface Region Imaging Spectrograph (IRIS). The core of this spectral line is formed at the top of the chromosphere and shows how the magnetic field structures the plasma which is aligned along dark, loop-like structures in this image. The bright regions are plage, regions of enhanced heating and temperatures in the chromosphere, caused by the strong magnetic fields that pierce through the Sun's surface at those locations. The Earth is shown to scale. The black horizontal lines are fiducial marks along the spectrograph slit that are used for internal co-alignment.
Image credit: Bart de Pontieu (LMSAL)
Observations by IRIS (NASA, LMSAL)