The Ultraviolet Coronagraph Spectrometer on the Solar and Heliospheric Observatory, UVCS/SOHO, and the Ultraviolet Coronal Spectrometer on the Spartan 201 satellite, UVCS/Spartaa, have been used to measure H I 1215.67 A line profiles in polar coronal holes of the Sun at projected heliocentric heights between 1.5 and 3.0 R@,. UVCS/SOHO also measured line profiles for H I 1025.72 A, 0 1’1 1032/1037 A, and Mg X 625 A. The reported UVCS/SOH~ observations were made between 5 April and 21 June 1996 and the UVCS/Spartan observations were made between 11 and 12 April 1993. Both sets of measurements indicate that a significant fraction of the protons along the line of sight in coronal holes have velocities larger than those for a Maxwellian velocity distribution at the expected electron temperature. Most probable speeds for OS+ velocity distributions along the &es of sight are sma.ller than those of Ho at 1.5 &, are comparable at about 1.7 Rn and become significantly larger than the Ho velocities above 2 G. There is a tendency for the 05+ line of sight velocity distribution in concentrations of polar plumes to be more narrow than those in regions away from such concentrations. UVCS/SOHO has identified 31 spectral lines in the extended solar corona.
Measurements of H I and O VI velocity distributions in the extended solar corona with UVCS/SOHO and UVCS/Spartan 201
NICOLOSI, PIERGIORGIO;NALETTO, GIAMPIERO;
1997
Abstract
The Ultraviolet Coronagraph Spectrometer on the Solar and Heliospheric Observatory, UVCS/SOHO, and the Ultraviolet Coronal Spectrometer on the Spartan 201 satellite, UVCS/Spartaa, have been used to measure H I 1215.67 A line profiles in polar coronal holes of the Sun at projected heliocentric heights between 1.5 and 3.0 R@,. UVCS/SOHO also measured line profiles for H I 1025.72 A, 0 1’1 1032/1037 A, and Mg X 625 A. The reported UVCS/SOH~ observations were made between 5 April and 21 June 1996 and the UVCS/Spartan observations were made between 11 and 12 April 1993. Both sets of measurements indicate that a significant fraction of the protons along the line of sight in coronal holes have velocities larger than those for a Maxwellian velocity distribution at the expected electron temperature. Most probable speeds for OS+ velocity distributions along the &es of sight are sma.ller than those of Ho at 1.5 &, are comparable at about 1.7 Rn and become significantly larger than the Ho velocities above 2 G. There is a tendency for the 05+ line of sight velocity distribution in concentrations of polar plumes to be more narrow than those in regions away from such concentrations. UVCS/SOHO has identified 31 spectral lines in the extended solar corona.
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