Bibcode
Kostik, R.; Khomenko, E.
Bibliographical reference
Astronomy and Astrophysics, Volume 589, id.A6, 7 pp.
Advertised on:
5
2016
Journal
Citations
16
Refereed citations
15
Description
This paper studies the dependence of the Ca ii H line core brightness on
the strength and inclination of the photospheric magnetic field, and on
the parameters of convective and wave motions in a facular region at the
center of the solar disc. We use three simultaneous data sets that were
obtained at the German Vacuum Tower Telescope (Observatorio del Teide,
Tenerife): (1) spectra of Ba ii 4554 Å line, registered with the
instrument TESOS to measure the variations of intensity and velocity
through the photosphere up to the temperature minimum; (2)
spectropolarimetric data in Fe i 1.56 μm lines (registered with the
instrument TIP II) to measure photospheric magnetic fields; (3)
filtergrams in Ca ii H that give information about brightness
fluctuations in the chromosphere. The results show that the Ca ii H
brightness in the facula strongly depends on the power of waves with
periods in the 5-min range, which propagate upwards, and also on the
phase shift between velocity oscillations at the bottom photosphere and
around the temperature minimum height that is measured from Ba ii line.
The Ca ii H brightness is maximum at locations where the phase shift
between temperature and velocity oscillations lies within
0°-100°. There is an indirect influence of convective motions on
the Ca ii H brightness. The higher the amplitude of convective
velocities is and the greater the height is where they change their
direction of motion, the brighter the facula. In summary, our results
lead to conclusions that facular regions appear bright not only because
of the Wilson depression in magnetic structures, but also owing to real
heating.