NDLI: Relative Velocities and Linewidths in a Coronal Hole and Outside

Content Provider	Springer Nature Link
Author	Raju, K. P.
Copyright Year	2009
Abstract	Relative Doppler velocities and spectral linewidths in a coronal hole and in the quiet Sun region outside have been obtained from Solar and Heliospheric Observatory (SOHO)/Coronal Diagnostic Spectrometer (CDS) observations. Five strong emission lines in the CDS wavelength range (namely, O iii 599 Å, O v 630 Å, Ne vi 562.8 Å, He ii 304 Å, and Mg ix 368 Å), whose formation temperatures represent different heights in the solar atmosphere from the lower transition region to the inner corona, have been used in the study. As reported earlier, relative velocities in the coronal hole are generally blueshifted with respect to the quiet Sun, and the magnitude of the blueshifts increases with height. It has been found that the polar coronal hole has larger relative velocities than the equatorial extension in the inner corona. Several localized velocity contours have been found mainly on network brightenings and in the vicinity of the coronal hole boundary. The presence of velocity contours on the network may represent network outflows whereas the latter could be due to localized jets probably arising from magnetic reconnection at the boundary. All spectral lines have larger widths in the coronal hole than in the quiet Sun. In O v 630 Å an extended low-linewidth region is seen in the coronal hole – quiet Sun boundary, which may indicate fresh mass transfer across the boundary. Also polar coronal holes have larger linewidths in comparison with the equatorial extension. Together with larger relative velocities, this suggests that the solar wind emanating from polar hole regions is faster than that from equatorial hole regions.
Starting Page	119
Ending Page	129
Page Count	11
File Format	PDF
ISSN	00380938
Journal	Solar Physics
Volume Number	255
Issue Number	1
e-ISSN	1573093X
Language	English
Publisher	Springer Netherlands
Publisher Date	2009-01-23
Publisher Place	Dordrecht
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	Coronal holes Spectrum, ultraviolet Transition region Extraterrestrial Physics, Space Sciences Meteorology/Climatology Astrophysics
Content Type	Text
Resource Type	Article
Subject	Astronomy and Astrophysics Space and Planetary Science

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