On the Lyman α and β lines in solar coronal streamers

N. Labrosse*, X. Li, B. Li

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Citations (SciVal)

Abstract

Aims. We investigate the formation of the H I 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.

Original languageEnglish
Pages (from-to)719-723
Number of pages5
JournalAstronomy and Astrophysics
Volume455
Issue number2
DOIs
Publication statusPublished - Aug 2006

Keywords

  • Line: formation
  • Line: profiles
  • Radiative transfer
  • Sun: corona
  • Sun: UV radiation

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