| タイトル | Areas of Polar Coronal Holes from 1996 Through 2010 |
| 本文（外部サイト） | http://hdl.handle.net/2060/20150007896 |
| 著者（英） | Kirk, M. S.; Webber, Hess S. A.; Pesnell, W. D.; Karna, N. |
| 著者所属（英） | NASA Goddard Space Flight Center |
| 発行日 | 2014-07-04 |
| 言語 | eng |
| 内容記述 | Polar coronal holes (PCHs) trace the magnetic variability of the Sun throughout the solar cycle. Their size and evolution have been studied as proxies for the global magnetic field. We present measurements of the PCH areas from 1996 through 2010, derived from an updated perimeter-tracing method and two synoptic-map methods. The perimeter tracing method detects PCH boundaries along the solar limb, using full-disk images from the SOlar and Heliospheric Observatory/Extreme ultraviolet Imaging Telescope (SOHO/EIT). One synoptic-map method uses the line-of-sight magnetic field from the SOHO/Michelson Doppler Imager (MDI) to determine the unipolarity boundaries near the poles. The other method applies thresholding techniques to synoptic maps created from EUV image data from EIT. The results from all three methods suggest that the solar maxima and minima of the two hemispheres are out of phase. The maximum PCH area, averaged over the methods in each hemisphere, is approximately 6 % during both solar minima spanned by the data (between Solar Cycles 22/23 and 23/24). The northern PCH area began a declining trend in 2010, suggesting a downturn toward the maximum of Solar Cycle 24 in that hemisphere, while the southern hole remained large throughout 2010. |
| NASA分類 | Solar Physics |
| レポートNO | GSFC-E-DAA-TN22860 |
| 権利 | Copyright, Distribution as joint owner in the copyright |
|
