Solar Spectroscopy and (Pseudo-)Diagnostics of the Solar Chromosphere

Abstract

I first review trends in current solar spectrometry and then concentrate on comparing various spectroscopic diagnostics of the solar chromosphere. Some are actually not at all chromospheric but just photospheric or clapotispheric and do not convey information on chromospheric heating, even though this is often assumed. Balmer Hα is the principal displayer of the closed-field chromosphere, but it is unclear how chromospheric fibrils gain their large Hα opacity. The open-field chromosphere seems to harbor most if not all coronal heating and solar wind driving, but is hardly seen in optical diagnostics.