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J. L. Kohl S. Fineschi R. Esser A. Ciaravella S. R. Cranmer L. D. Gardner R. Suleiman G. Noci A. Modigliani 《Space Science Reviews》1999,87(1-2):233-236
Ultraviolet emission line profiles have been measured on 15-29 September 1997 for H I 1216 Å, O VI 1032, 1037 Å and Mg X 625 Å in a polar coronal hole, at heliographic heights ? (in solar radii) between 1.34 and 2.0. Observations of H I 1216 Å and the O VI doublet from January 1997 for ? = 1.5 to 3.0 are provided for comparison. Mg X 625 Å is observed to have a narrow component at ? = 1.34 which accounts for only a small fraction of the observed spectral radiance, and a broad component that exists at all observed heights. The widths of O VI broad components are only slightly larger than those for H I at ? = 1.34, but are significantly larger at ? = 1.5 and much larger for ? > 1.75. In contrast, the Mg X values are less than those of H I up to 1.75 and then increase rapidly up to at least ? = 2.0, but never reach the values of O VI. 相似文献
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John C. Raymond Raid Suleiman John L. Kohl Giancarlo Noci 《Space Science Reviews》1998,85(1-2):283-289
A great deal of evidence for elemental abundance variations among different structures in the solar corona has accumulated
over the years. Many of the observations show changes in the relative abundances of high- and low-First Ionization Potential
elements, but relatively few show the absolute elemental abundances. Recent observations from the SOHO satellite give absolute
abundances in coronal streamers. Along the streamer edges, and at low heights in the streamer, they show roughly photospheric
abundances for the low-FIP elements, and a factor of 3 depletion of high-FIP elements. In the streamer core at 1.5 R·, both
high- and low-FIP elements are depleted by an additional factor of 3, which appears to result from gravitational settling.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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R. M. Suleiman J.L. Kohl A. V. Panasyuk A. Ciaravella S.R. Cranmer L.D. Gardner R. Frazin R. Hauck P.L. Smith G. Noci 《Space Science Reviews》1999,87(1-2):327-330
The Ultraviolet Coronagraph Spectrometer (UVCS) on the Solar and Heliospheric Observatory (SOHO) has been used to measure
spectral line profiles for H I Lyα in the south polar coronal hole at projected heliocentric heights 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 Lyα profile is the only one observable with UVCS above 3.5 R⊙ in coronal holes. Within this region the outflowing coronal plasma becomes nearly collisionless and the ionization balance
is believed to become frozen.
In this paper, the 1/e half widths of the coronal velocity distributions are 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 interplanetary H I Lyα. The half widths were found to increase with projected heliographic
height from 1.5 to 2.5 R⊙ and decrease with height from 3.5 to 5 R⊙.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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