Bibcode
Kostik, R.; Khomenko, E.
Bibliographical reference
Astronomy and Astrophysics, Volume 545, id.A22
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9
2012
Journal
Citations
24
Refereed citations
20
Description
Aims: We study the properties of solar granulation in a facular
region from the photosphere up to the lower chromosphere. Our aim is to
investigate the dependence of granular structure on magnetic field
strength. Methods: We used observations obtained at the German
Vacuum Tower Telescope (Observatorio del Teide, Tenerife) using two
different instruments: the Triple Etalon SOlar Spectrometer (TESOS) to
measure velocity and intensity variations along the photosphere in the
Ba ii 4554 Å line; and, simultaneously, the Tenerife Infrared
Polarimeter (TIP-II) to the measure Stokes parameters and the magnetic
field strength at the lower photosphere in the Fe i 1.56 μm lines.
Results: We find that the convective velocities of granules in
the facular area decrease with magnetic field while the convective
velocities of intergranular lanes increase with the field strength.
Similar to the quiet areas, there is a contrast and velocity sign
reversal taking place in the middle photosphere. The reversal heights
depend on the magnetic field strength and are, on average, about 100 km
higher than in the quiet regions. The correlation between convective
velocity and intensity decreases with magnetic field at the bottom
photosphere, but increases in the upper photosphere. The contrast of
intergranular lanes observed close to the disk center is almost
independent of the magnetic field strength. Conclusions: The
strong magnetic field of the facular area seems to stabilize the
convection and to promote more effective energy transfer in the upper
layers of the solar atmosphere, since the convective elements reach
greater heights.
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