Sunspot chromosphere
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The amazing chromosphere above an active region (3/3)
Dunn Solar Telescope
Sunspots are the largest manifestation of magnetic fields in the solar photosphere and appear darker than the surrounding photosphere in which convective heat transport takes place in the form of granulation. The details of the heat transport within sunspots are still under debate. It is clear, however, that it is of convective origin. The convective transport of heat must take place even in the coolest parts of sunspots, since neither heat conduction nor radiative heat transport suffices to sustain the observed umbral temperatures.
The image shows active region 11092 as observed on 2010 August 3 with the IBIS instrument at the Dunn Solar Telescope (New Mexico, USA). It is a speckle-reconstructed intensity map in the core of the H-alpha 6563 Å line. The chromospheric fibrillar structure visible in this line is much enhanced in the extended active region area. The small, roundish bright points mostly visible at the periphery of the FOV correspond to instances of acoustic shocks in the mid-chromosphere. The brightening to the left of the spot is due to a sub-flare occurring in the region at the time of acquisition.
Image credit: Kevin Reardon (INAF-Arcetri, National Solar Observatory/AURA/NSF)
Observations by IBIS (INAF/NSO/QUB)