On the Lyman α and β lines in solar coronal streamers

Labrosse, N. , Li, X. and Li, B. (2006) On the Lyman α and β lines in solar coronal streamers. Astronomy and Astrophysics, 455(2), pp. 719-723. (doi: 10.1051/0004-6361:20065059)

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Publisher's URL: http://dx.doi.org/10.1051/0004-6361:20065059


Aims: We investigate the formation of the HI Lyman α and Lyman β lines in an equatorial coronal streamer. Particular attention is paid to frequency redistribution for the scattering of the incident radiation. The properties of the spectral lines are studied. Methods: The coronal model is given by a global 2.5D three fluid solar wind model with α particles. The emergent intensities and line profiles are calculated from the solution of the statistical equilibrium and radiative transfer equations for an hydrogen atom with 11 energy levels under non local thermodynamic equilibrium. The formation of the lines results from radiative excitation, collisional excitation, and takes into account the coupling with all other transitions between the hydrogen energy levels. Results: We present new estimates of the radiative and collisional contributions of the Lyman line intensities within the streamer. It is also shown that within the streamer, the full width at half-maximum (FWHM) of the Lyman β line is a better indicator of the plasma temperature than that of Lyman α. These results show that care should be taken when inferring the proton temperature from the Lyman α line profile as observed in coronal streamers, e.g. by the Ultraviolet Coronagraph Spectrometer or the Solar Ultraviolet Measurements of Emitted Radiation experiments on board the Solar and Heliospheric Observatory.

Item Type:Articles
Keywords:Line - formation, line - profiles, radiative transfer, sun - corona, sun - UV radiation
Glasgow Author(s) Enlighten ID:Labrosse, Dr Nicolas
Authors: Labrosse, N., Li, X., and Li, B.
Subjects:Q Science > QB Astronomy
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Astronomy and Astrophysics
Publisher:EDP Sciences
ISSN (Online):1432-0746
Copyright Holders:Copyright © 2006 EDP Sciences
First Published:First published in Astronomy and Astrophysics 455(1):719-723
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher.

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