Results of observations of wave motions in the Solar facula

Heading: 
1Shchukina, NG, 1Kostyk, RI
1Main Astronomical Observatory of the National Academy of Sciences of Ukraine, Kyiv, Ukraine
Kinemat. fiz. nebesnyh tel (Online) 2022, 38(1):71-89
https://doi.org/10.15407/kfnt2022.01.071
Start Page: Solar physics
Language: Ukrainian
Abstract: 

The results of spectropolarimetric and filter observations of the facular region in the lines Fe I 1564.3, Fe I 1565.8 nm, Ba II 455.4 nm, and Ca II H 396.8 nm obtained near the solar disk center at the German Vacuum Tower Telescope (Tenerife, Spain) are discussed. It is shown that the facular contrast measured at the Ca II H line center first grows more and more slowly with magnetic field strength, and then, with its further increase goes down. The reason for this is the nonlinear height dependence of the line source function caused by a deviation from local thermodynamic equilibrium. It was found that waves propagating both upward and downward can be observed in any area of the facula, regardless of its brightness. Moreover, in bright areas with the strong magnetic field, upward waves dominate, while in less bright areas with the weaker field, downward waves are more often observed. The facular contrast measured at the center of the Ca II H line is shown to correlate with the power of the wave velocity oscillations. In bright areas, it grows with the power, it does not matter in which direction the waves are propagating. In the areas with low brightness, the opposite dependence is observed for both types of waves. The power of the wave velocity oscillations, in turn, is sensitive to the magnetic field strength. In the facular bright magnetic elements the stronger the field, the higher the power of oscillations for both upward and downward waves. In the case of reduced brightness, the inverse relationship is observed. We conclude that the increase in contrast with the wave velocity power which is observed in the bright facular regions can be considered as evidence that these areas look bright not only because of the Wilson depression, but also because of heating of the solar plasma by waves.

Keywords: magnetic fields, solar activity, solar faculae, spectropolarimetric observations, thermodynamic conditions