Solar EUV and UV Emission Line Observations Above a Polar Coronal Hole

The roll manoeuvre of SOHO on September 3, 1997 provided the opportunity to study the northern coronal hole with SUMER slits in east-west orientation, so that polar plumes and inter-plume lanes could be observed simultaneously. A preliminary analysis of the observations shows that lines emitted by i...

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Bibliographic Details
Published inSpace science reviews Vol. 85; no. 1-2; pp. 371 - 378
Main Authors Wilhelm, K, Bodmer, R
Format Journal Article
LanguageEnglish
Published Dordrecht Springer Nature B.V 01.01.1998
Subjects
Corona
Ionization
Magnesium
Neon
Plumes
Solar physics
Studies
Ultraviolet radiation
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Summary:The roll manoeuvre of SOHO on September 3, 1997 provided the opportunity to study the northern coronal hole with SUMER slits in east-west orientation, so that polar plumes and inter-plume lanes could be observed simultaneously. A preliminary analysis of the observations shows that lines emitted by ions with the lowest formation temperatures (with the exceptions of Ne^sup 7+^ and Ar^sup 7+^) have the largest ratios of plume to lane radiances at heights between 35 000 km and 70 000 km above the photosphere. All lines have narrower widths inside plumes than outside. Electron densities have been deduced in plumes and lanes from Si VIII and Mg VIII line radiance ratios. The Mg IX pair was used to determine the corresponding electron temperatures. Neon (with a high first-ionization potential) is found to be less abundant relative to magnesium (with low FIP) in a plume compared to an inter-plume lane, but the variation is smaller than previously determined Ne/Mg abundance ratios in a plume relative to the photosphere.[PUBLICATION ABSTRACT]
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ISSN:0038-6308
1572-9672
DOI:10.1023/A:1005187509676