Power spectra of solar brightness variations at different inclinations
File(s)
Working paper
Author(s)
Type
Working Paper
Abstract
Magnetic features on the surfaces of cool stars cause variations of their
brightness. Such variations have been extensively studied for the Sun. Recent
planet-hunting space telescopes allowed measuring brightness variations in
hundred thousands of other stars. The new data posed the question of how
typical is the Sun as a variable star. Putting solar variability into the
stellar context suffers, however, from the bias of solar observations being
made from its near-equatorial plane, whereas stars are observed at all possible
inclinations. We model solar brightness variations at timescales from days to
years as they would be observed at different inclinations. In particular, we
consider the effect of the inclination on the power spectrum of solar
brightness variations. The variations are calculated in several passbands
routinely used for stellar measurements. We employ the Surface Flux Transport
Model (SFTM) to simulate the time-dependent spatial distribution of magnetic
features on both near- and far-sides of the Sun. This distribution is then used
to calculate solar brightness variations following the SATIRE (Spectral And
Total Irradiance REconstruction) approach. We have quantified the effect of the
inclination on solar brightness variability at timescales down to a day. Thus,
our results allow making solar brightness records directly comparable to those
obtained by the planet-hunting space telescopes. Furthermore, we decompose
solar brightness variations into the components originating from the solar
rotation and from the evolution of magnetic features.
brightness. Such variations have been extensively studied for the Sun. Recent
planet-hunting space telescopes allowed measuring brightness variations in
hundred thousands of other stars. The new data posed the question of how
typical is the Sun as a variable star. Putting solar variability into the
stellar context suffers, however, from the bias of solar observations being
made from its near-equatorial plane, whereas stars are observed at all possible
inclinations. We model solar brightness variations at timescales from days to
years as they would be observed at different inclinations. In particular, we
consider the effect of the inclination on the power spectrum of solar
brightness variations. The variations are calculated in several passbands
routinely used for stellar measurements. We employ the Surface Flux Transport
Model (SFTM) to simulate the time-dependent spatial distribution of magnetic
features on both near- and far-sides of the Sun. This distribution is then used
to calculate solar brightness variations following the SATIRE (Spectral And
Total Irradiance REconstruction) approach. We have quantified the effect of the
inclination on solar brightness variability at timescales down to a day. Thus,
our results allow making solar brightness records directly comparable to those
obtained by the planet-hunting space telescopes. Furthermore, we decompose
solar brightness variations into the components originating from the solar
rotation and from the evolution of magnetic features.
Date Issued
2020-02-25
Citation
2020
Publisher
arXiv
Copyright Statement
© 2020 Tha Author(s)
Identifier
http://arxiv.org/abs/2002.10895v1
Subjects
astro-ph.SR
astro-ph.SR
Notes
11 pages, 9 figures plus 3 additional figures in the appendix, accepted for publication in Astronomy & Astrophysics