Solar Hα excess during Solar Cycle 24 from full-disk filtergrams of the Chromospheric Telescope
arXiv:2203.04357 · doi:10.1051/0004-6361/202040091
Abstract
The chromospheric H-alpha spectral line is a strong line in the spectrum of the Sun and other stars. In the stellar regime, this spectral line is already used 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 of full-disk H-alpha filtergrams of the Chromospheric Telescope (ChroTel) to extract the imaging H-alpha excess and deficit, which are related to bright features (plage regions) and dark absorption features (filaments and sunspots), respectively. The aim of this study is to introduce the imaging H-alpha excess and deficit as tracers of solar activity and compare them to other established indicators: the relative sunspot number, the F10.7cm radio flux, and the MgII index. The H-alpha excess and deficit follow the behavior of the solar activity over the course of the cycle, whereby the peak of the H-alpha deficit is shortly after the solar maximum. The H-alpha excess is closely correlated to the chromospheric MgII index. The highest correlation of the H-alpha deficit is found with the F10.7cm radio flux. The H-alpha deficit reflects the cyclic behavior of polar crown filaments and their disappearance shortly before the solar maximum. We investigated the mean intensity distribution for H-alpha excess regions for solar minimum and maximum, whereby the shape of the distributions is very similar, but with different amplitudes. Furthermore, we investigate whether the area coverage fraction or the changing H-alpha excess in the active regions dominates temporal variability in solar H-alpha observations. The area coverage fraction and the H-alpha excess are strongly correlated, whereas the weak correlation between the area coverage fraction and mean intensity leaves us pessimistic that the degeneracy between these two quantities can be broken for the modeling of unresolved stellar surfaces.
14 pages, 8 Figures
References in corpus (19)
- A planet within the debris disk around the pre-main-sequence star AU Microscopii
- On Polar Magnetic Field Reversal and Surface Flux Transport During Solar Cycle 24
- Four newborn planets transiting the young solar analog V1298 Tau
- Placing the spotted T Tauri star LkCa 4 on an HR diagram
- Discovery of a 1.6-year Magnetic Activity Cycle in the Exoplanet Host Star iota Horologii
- Sun-as-a-Star Spectrum Variations 1974-2006
- The Starspots of HAT-P-11: Evidence for a Solar-like Dynamo
- Evidence for photometric activity cycles in 3203 Kepler stars
- Relation between photospheric magnetic field and chromospheric emission
- Analysis of full disc Ca II K spectroheliograms III. Plage area composite series covering 1892-2019
- Solar cycle indices from the photosphere to the corona: measurements and underlying physics
- Three-dimensional radiative transfer simulations of the scattering polarization of the hydrogen Ly line in a MHD model of the chromosphere-corona transition region
- Transiting the Sun: The impact of stellar activity on X-ray and ultraviolet transits
- Temporal evolution and correlations of optical activity indicators measured in Sun-as-a-star observations
- Fifteen years in the high-energy life of the solar-type star HD 81809. XMM-Newton observations of a stellar activity cycle
- Starspot rotation rates vs. activity cycle phase: Butterfly diagrams of Kepler stars are unlike the Sun's
- Chromospheric Synoptic Maps of Polar Crown Filaments
- Calibration of full-disk He I 10830 Å filtergrams of the Chromospheric Telescope
- Solar Atmosphere Radiative Transfer Model Comparison based on 3D MHD simulations