Bibcode
Rezaei, R.; Bruls, J. H. M. J.; Schmidt, W.; Beck, C.; Kalkofen, W.; Schlichenmaier, R.
Referencia bibliográfica
Astronomy and Astrophysics, Volume 484, Issue 2, 2008, pp.503-509
Advertised on:
6
2008
Revista
Número de citas
30
Número de citas referidas
29
Descripción
Aims: We study chromospheric emission to understand the temperature
stratification in the solar chromosphere. Methods: We observed
the intensity profile of the Ca II H line in a quiet Sun region close to
the disk center at the German Vacuum Tower Telescope. We analyze over
105 line profiles from inter-network regions. For comparison
with the observed profiles, we synthesize spectra for a variety of model
atmospheres with a non local thermodynamic equilibrium (NLTE) radiative
transfer code. Results: A fraction of about 25% of the observed
Ca II H line profiles do not show a measurable emission peak in
H2v and H2r wavelength bands (reversal-free). All
of the chosen model atmospheres with a temperature rise fail to
reproduce such profiles. On the other hand, the synthetic calcium
profile of a model atmosphere that has a monotonic decline of the
temperature with height shows a reversal-free profile that has much
lower intensities than any observed line profile. Conclusions:
The observed reversal-free profiles indicate the existence of cool
patches in the interior of chromospheric network cells, at least for
short time intervals. Our finding is not only in conflict with a
full-time hot chromosphere, but also with a very cool chromosphere as
found in some dynamic simulations.
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