Astronomy and Astrophysics – Astrophysics
Scientific paper
Jun 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995sowi.confq..68f&link_type=abstract
Harvard-Smithsonian Center for Astrophysics, International Solar Wind 8 Conference, p. 68
Astronomy and Astrophysics
Astrophysics
Lyman Alpha Radiation, Electron Energy, Electron Distribution, Coronal Holes, Temperature, Ultraviolet Spectrometers, Soho Mission, Coronagraphs
Scientific paper
The electron temperature is a fundamental physical parameter of the coronal plasma. Currently, there are no direct measurements of this quantity in the extended corona. Observations with the Ultraviolet Coronagraph Spectrometer (UVCS) aboard the upcoming Solar and Heliospheric Observatory (SOHO) mission can provide the most direct determination of the electron kinetic temperature (or, more precisely, the electron velocity distribution along the line of sight). This measurement is based on the observation of the Thomson-scattered Lyman alpha (Ly-alpha) profile. This observation is made particularly challenging by the fact that the integrated intensity of the electron-scattered Ly-alpha line is about 103 times fainter than that of the resonantly-scattered Ly-alpha component. In addition, the former is distributed across 50 A (FWHM), unlike the latter that is concentrated in 1 A. These facts impose stringent requirements on the stray-light rejection properties of the coronagraph/spectrometer, and in particular on the requirements for the grating. We make use of laboratory measurements of the UVCS Ly-alpha grating stray-light, and of simulated electron-scattered Ly-alpha profiles to estimate the expected confidence levels of electron temperature determination. Models of different structures typical of the corona (e.g., streamers, coronal holes) are used for this parameter study.
Esser Ruth
Fineschi Silvano
Huber Martin C. E.
Karovska Magarita
Kohl John L.
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