Sunspot chromosphere
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The amazing chromosphere above an active region (1/3)
Dunn Solar Telescope
Sunspots are the largest manifestation of magnetic fields in the solar photosphere. They appear darker than the surrounding photosphere, where convective heat transport takes place in the form of granulation. The details of energy transport within sunspots are still under debate. It is clear, however, that it must be of convective origin. Convective energy transport must occur even in the coolest parts of sunspots, since neither heat conduction nor radiative heat transport suffices to sustain the observed umbral temperatures.
This wide-field mosaic shows active region 11092 at different wavelengths as observed on 2010 August 3 with the IBIS instrument at the Dunn Solar Telescope (New Mexico, USA). From bottom to top we have: (1) broadband continuum around 6200 Å showing the leading, mature sunspot, as well as several pores in the area of trailing polarity (photosphere). The granulation pattern is well resolved. (2) Line core minimum position intensity of the Fe I 5434 Å spectral line (upper photosphere). (3) Ca II 8542 Å line core intensity, sampling the mid-chromosphere. (4) H-alpha line core intensity, sampling the upper chromosphere. 5) AIA image at 171 Å, showing the corona.
Image credit: Kevin Reardon (INAF-Arcetri, National Solar Observatory/AURA/NSF)
Observations by IBIS (INAF/NSO/QUB)