Current helicity of the large-scale photospheric magnetic field

被引:46
作者
Pevtsov, AA
Latushko, SM
机构
[1] Department of Physics, Montana State University, Bozeman
[2] Inst. of Solar Terrestrial Physics, Irkutsk 664033
关键词
Sun : activity; Sun : magnetic fields;
D O I
10.1086/308227
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
This paper presents the first results of a study of current helicity of the large-scale magnetic field (LSMF) using full-disk longitudinal B-long magnetograms from the Michelson Doppler Imager on board the SOHO spacecraft. We employ a known technique to reconstruct the vector magnetic field under the assumption of relatively slow evolution of the LSMF and treat the variations of B-long, occurring during a defined period of time as the result of the changing projection angle only. We compute the synoptic maps of radial (B-r) and toroidal (B-lambda) magnetic fields and the latitudinal profile of current helicity density h(c) = B-r(del x B)(r). For eight solar rotations (1910-1917) that have been analyzed, h(c) shows significant variations within +/-40 degrees of solar latitude with no strong hemispheric sign asymmetry. Asymmetry is present, however, in high latitudes, where h(c) is negative/positive in the northern/southern hemisphere.
引用
收藏
页码:999 / 1003
页数:5
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