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The chromospheric H-alpha spectral line is a strong line in the spectrum ofthe Sun and other stars. In the stellar regime, this spectral line is alreadyused as a powerful tracer of stellar activity. For the Sun, other tracers (i.e,CaII K) are typically used to monitor solar activity. We used observations offull-disk H-alpha filtergrams of the Chromospheric Telescope (ChroTel) toextract the imaging H-alpha excess and deficit, which are related to brightfeatures (plage regions) and dark absorption features (filaments and sunspots),respectively. The aim of this study is to introduce the imaging H-alpha excessand deficit as tracers of solar activity and compare them to other establishedindicators: the relative sunspot number, the F10.7cm radio flux, and the MgIIindex. The H-alpha excess and deficit follow the behavior of the solar activityover the course of the cycle, whereby the peak of the H-alpha deficit isshortly after the solar maximum. The H-alpha excess is closely correlated tothe chromospheric MgII index. The highest correlation of the H-alpha deficit isfound with the F10.7cm radio flux. The H-alpha deficit reflects the cyclicbehavior of polar crown filaments and their disappearance shortly before thesolar maximum. We investigated the mean intensity distribution for H-alphaexcess regions for solar minimum and maximum, whereby the shape of thedistributions is very similar, but with different amplitudes. Furthermore, weinvestigate whether the area coverage fraction or the changing H-alpha excessin the active regions dominates temporal variability in solar H-alphaobservations. The area coverage fraction and the H-alpha excess are stronglycorrelated, whereas the weak correlation between the area coverage fraction andmean intensity leaves us pessimistic that the degeneracy between these twoquantities can be broken for the modeling of unresolved stellar surfaces.

Solar H{\alpha} excess during Solar Cycle 24 from full-disk filtergrams of the Chromospheric Telescope