The flux deficits in star spots

Abstract

The bolometric flux deficits of the photospheres of spotted stars are derived for the first time in the framework of zonal spottedness models for red dwarfs computed at the Crimean Astrophysical Observatory. The resulting flux deficits are compared to the estimated radiative losses from the chromospheres and coronas measured during quasi-simultaneous observations. A linear correlation is found between the logarithms of these quantities, with the Sun fitting these relations. Radiative losses from the outer stellar atmospheres in quiescence and during individual sporadic flares are significantly lower than the bolometric deficits of the spotted photospheres of active stars. This suggests that the flux deficit due to spots leads to global reconstruction of the atmospheres of red dwarfs, analogous to the local atmospheric reconstruction that occurs during solar and stellar flares. This process may be realized via the superposition of a large number of weak impulsive flares and other dynamic events, which develop on these stars and heat their coronas (i.e., in this view, microflaring is favored as the principal coronal heating mechanism for these stars). A brief analysis of the long-term variations in the chromospheric and photospheric radiation of F-K stars from the HK project and of the Sun suggests that such dynamical reconstruction of the outer atmosphere by energy associated with the flux deficit of the spotted photosphere occurs at times of increased surface activity in all F-M stars.