Latitudinal properties of the Lyman and O VI profiles in the extended solar corona
L. Zangrilli 1,2,
P. Nicolosi 1,2,
G. Poletto 3,
G. Noci 4,
M. Romoli 3 and
J.L. Kohl 5
Received 15 September 1998 / Accepted 9 November 1998
We have analysed the latitudinal properties of the profiles of the line at and of the doublet at and in the extended solar corona, between and . Observations have been performed with the UltraViolet Coronagraph Spectrometer (UVCS) on board the ESA-NASA solar satellite SOHO (SOlar and Heliospheric Observatory). The results show that these lines have quite a different behaviour with latitude: the line has larger full width at half maximum (FWHM) values in the streamer region and narrower ones towards polar latitudes, while the lines have a minimum FWHM at the center of the streamer, which almost steadily increases towards polar regions. The observations have been analysed looking also for an interpretation in terms of selective heating mechanisms. The implications of our results for coronal heating theories are also examined. In particular we discuss the possibility for the presence of the ion-cyclotron coronal heating mechanism. Moreover, we point out an interesting correlation between the intensity of the coronal lines and their widths, which may be relevant to the open question of the different morphological features visible in the and lines.
Key words: line: profiles Sun: corona Sun: solar wind Sun: UV radiation
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© European Southern Observatory (ESO) 1999
Online publication: February 22, 1999