Issue |
A&A
Volume 484, Number 2, June III 2008
|
|
---|---|---|
Page(s) | 503 - 509 | |
Section | The Sun | |
DOI | https://doi.org/10.1051/0004-6361:20079050 | |
Published online | 16 April 2008 |
Reversal-free Ca II H profiles: a challenge for solar chromosphere modeling in quiet inter-network
1
Kiepenheuer-Institut für Sonnenphysik, Schöneckstr. 6, 79104 Freiburg, Germany e-mail: [rrezaei;bruls;wolfgang;schliche]@kis.uni-freiburg.de
2
Instituto de Astrofísica de Canarias (IAC), Via Láctea, E 38 205, La Laguna, Spain e-mail: cbeck@iac.es
3
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA e-mail: wolf@cfa.harvard.edu
Received:
12
November
2007
Accepted:
11
March
2008
Aims. We study chromospheric emission to understand the temperature stratification in the solar chromosphere.
Methods. We observed the intensity profile of the 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 H line
profiles do not show a measurable emission peak
in
and
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.
Key words: Sun: chromosphere / Sun: atmosphere
© ESO, 2008
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