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arXiv · 0804.2325

Reversal-free CaIIH profiles: a challenge for solar chromosphere modeling in quiet inter-network

R. Rezaei·J. H. M. J. Bruls·W. Schmidt·C. Beck·W. Kalkofen·R. Schlichenmaier
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Abstract

We study chromospheric emission to understand the temperature stratification in the solar chromosphere. We observed the intensity profile of the CaIIH line in a quiet Sun region close to the disk center at the German Vacuum Tower Telescope. We analyze over 10^5 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. A fraction of about 25% of the observed CaIIH line profiles do not show a measurable emission peak in H_{2v} and H_{2r} 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. 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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R. Rezaei, J. H. M. J. Bruls, W. Schmidt, C. Beck, W. Kalkofen, R. Schlichenmaier. 2008-04-15. Reversal-free CaIIH profiles: a challenge for solar chromosphere modeling in quiet inter-network. https://doi.org/10.1051/0004-6361:20079050

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