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| Paper: |
Comparison of SPARTAN and UVCS/SOHO Observations |
| Volume: |
154, Cool Stars, Stellar Systems and the Sun: Tenth Cambridge Workshop |
| Page: |
607 |
| Authors: |
Dobrzycka, D.; Strachan, L.; Miralles, M. P.; Kohl, J. L.; Gardner, L. D.; Smith, P. L.; Cranmer, S. R.; Guhathakurta, M.; Fisher, R. |
| Abstract: |
We present a comparison of the H 1 Lyalpha Spartan Ultraviolet Coronal Spectrometer observations of the north and south polar coronal holes in 1993-1995 with SOHO Ultraviolet Coronograph Spectrometer data obtained near solar minimum. These data span several years of the declining phase of the current solar cycle. Detailed analysis of the data revealed that the average H 1 Lyalpha intensities at similar heights decreased towards solar minimum in both polar coronal hole regions. In 1993 we observed a 15% - 40% scatter in the intensities measured at the same height but different position angles within the same coronal hole. Towards solar minimum the scatter was clearly reduced. Also the shape of the Lyalpha profile changed over the last four years. The narrow component present in 1993 data being attributed to the contribution from streamers along the line-of-sight disappeared in 1996/97. We interpret these effects as mainly due to a decrease in the number of high latitude streamers. At solar minimum streamers occupy mostly the equatorial region and do not contribute to the line-of-sight intensity as much as in 1993. |
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