UVCS/SOHO observations of HI Lyman alpha line profiles in coronal holes atheliocentric heights above 3.0 R-circle dot

Citation
Rm. Suleiman et al., UVCS/SOHO observations of HI Lyman alpha line profiles in coronal holes atheliocentric heights above 3.0 R-circle dot, SPACE SCI R, 87(1-2), 1999, pp. 327-330
Citations number
11
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Space Sciences
Journal title
SPACE SCIENCE REVIEWS
ISSN journal
0038-6308 → ACNP
Volume
87
Issue
1-2
Year of publication
1999
Pages
327 - 330
Database
ISI
SICI code
0038-6308(1999)87:1-2<327:UOOHLA>2.0.ZU;2-3
Abstract
The Ultraviolet Coronagraph Spectrometer (UVCS) on the Solar and Heliospher ic Observatory (SOHO) has been used to measure spectral line profiles for H I Ly alpha in the south polar coronal hole at projected heliocentric heigh ts from 3.5 to 6.0 R. during 1998 January 5-11. Observations from 1.5 to 2. 5 R. were made for comparison. The H I Ly alpha profile is the only one obs ervable with UVCS above 3.5 Ro in coronal holes. Within this region the out flowing coronal plasma becomes nearly collisionless and the ionization bala nce is believed to become frozen. In this paper, the 1/e half widths of the coronal velocity distributions ar e provided for the observed heights. The velocity distributions include all motions contributing to the velocities along the line of sight (LOS). The observations have been corrected for instrumental effects and interplanetar y H I Ly alpha. The half widths were found to increase with projected helio graphic height from 1.5 to 2.5 R. and decrease with height from 3.5 to 5 R. .