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Astron. Astrophys. 347, 676-683 (1999)
Proton and hydrogen temperatures at the base of the solar polar corona
E. Marsch 1,
C.-Y. Tu 1,2,
P. Heinzel 3,
K. Wilhelm 1 and
W. Curdt 1
1 Max-Planck-Institut für Aeronomie, D-37191 Katlenburg-Lindau, Germany
2 Department of Geophysics, Peking University, Beijing, 100871, P.R. China
3 Astronomical Institute, Academy of Sciences of the Czech Republic, CZ-25165 Ond
ejov, Czech Republic
Received 11 February 1999 / Accepted 19 May 1999
Abstract
The SUMER (Solar Ultraviolet Measurements of Emitted Radiation)
Spectrometer on SOHO (Solar and Heliospheric Observatory) has been
used to observe the lines of the Lyman series (up to quantum numbers
larger than 20) of hydrogen emitted in the solar atmosphere. The line
shapes and intensities versus height are obtained near the limb from
about -10" to 70". The lines are broad and show the typical
self-absorption reversal near the limb, where the emission comes from
optically thick material, and change systematically with increasing
height. The H I Ly6, Ly7 and Ly9 lines attain a
Gaussian shape at heights above the visible limb between about 19" and
22", where the emission comes from an optically thin plasma. The line
shapes and intensities can be fitted well by model profiles obtained
from multilevel NLTE (Non Local-Thermodynamic-Equilibrium) radiative
transfer calculations which allow us, assuming excitation and
ionization equilibrium, to derive consistently the temperatures and
densities of the hydrogen atoms and, with additional assumptions, of
the protons. Temperature values range between
1 ![[FORMULA]](img1.gif)
K to
2 K. We present the
systematics of the line shapes as observed in different emission
regions and discuss briefly the relevance of these results for the
solar wind acceleration and coronal heating.
Key words: line:
profiles 
Sun: corona
Sun: UV radiation
Send offprint requests to: E. Marsch (marsch@linmpi.mpg.de)
This article contains no SIMBAD objects.
Contents
- 1. Introduction
- 2. Observations and data reduction
- 3. Observational results and analysis
- 4. Model calculations
- 5. Summary and conclusions
- Acknowledgements
- References
© European Southern Observatory (ESO) 1999
Online publication: June 30, 1999
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