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Determining coronal electron temperatures from observations with UVCS/SOHOThe 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 10(exp 3) 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.
Document ID
19960021379
Document Type
Conference Paper
Authors
Fineschi, S. (Harvard-Smithsonian Center for Astrophysics Cambridge, MA United States)
Esser, R. (Harvard-Smithsonian Center for Astrophysics Cambridge, MA United States)
Habbal, S. R. (Harvard-Smithsonian Center for Astrophysics Cambridge, MA United States)
Karovska, M. (Harvard-Smithsonian Center for Astrophysics Cambridge, MA United States)
Romoli, M. (Harvard-Smithsonian Center for Astrophysics Cambridge, MA United States)
Strachan, L. (Harvard-Smithsonian Center for Astrophysics Cambridge, MA United States)
Kohl, J. L. (Harvard-Smithsonian Center for Astrophysics Cambridge, MA United States)
Huber, M. C. E. (European Space Agency. European Space Research and Technology Center, ESTEC Noordwijk, Netherlands)
Date Acquired
August 17, 2013
Publication Date
June 30, 1995
Publication Information
Publication: International Solar Wind 8 Conference
Subject Category
Solar Physics
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.