The detection of a new kind of sunspot-associated source in which the emission comes predominantly from a ring structure with size between that of the umbra and the penumbra is reported. The absence of emission from the center of the spot is interpreted in terms of the orientation of the magnetic field and the presence of low temperature material above the umbra.
No takes yet. Share an insight, caveat, or question.
Alissandrakis et al. (1982) studied this question.