Volume 455, Number 2, August IV 2006
|Page(s)||719 - 723|
|Published online||04 August 2006|
On the Lyman α and β lines in solar coronal streamers
Institute of Mathematical and Physical Sciences, University of Wales Aberystwyth, Ceredigion, SY23 3BZ, UK e-mail: [nll;xxl;bbl]@aber.ac.uk
Accepted: 10 May 2006
Aims.We investigate the formation of the 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.
Key words: line: formation / line: profiles / radiative transfer / Sun: corona / Sun: UV radiation
© ESO, 2006
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.