The Relative Umbral Area in Spot Groups as an Index of Cyclic Variation of Solar Activity
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- 作者：N. G. Bludova (1)
V. N. Obridko (1)
O. G. Badalyan (1) - 关键词：Sunspots ; Sunspot group structure ; Relative umbral area ; Cyclic variation of activity
- 刊名：Solar Physics
- 出版年：2014
- 出版时间：March 2014
- 年：2014
- 卷：289
- 期：3
- 页码：1013-1028
- 全文大小：
- 作者单位：N. G. Bludova (1)
V. N. Obridko (1)
O. G. Badalyan (1)
1. Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Russian Academy of Sciences, 142190, Troitsk, Russia - ISSN：1573-093X
文摘
The Greenwich series of data was used to study the ratio [q] of the total umbra area to the total area of the sunspot group (for brevity elative umbral area for the period 18741976. It was revealed that the annual mean value of q varied in time from 0.15 to 0.28 and reached its maximum in the early 1930s. The dependence of q on the sunspot group area [S] was considered to show that the smallest groups, of area less than 100m.v.h. (millionths of the visible hemisphere), contributed most significantly to the temporal variation of q. In contrast to the earlier results, the dependence obtained proved to be rather complicated. The coefficients of the linear expansion q(S) are themselves dependent on the sunspot-group area and time [t]; i.e. the relation of q to both S and t is nonlinear. Only in sunspot groups with a large area does dependence disappear, and q becomes constant, equal to 0.18. This is the value given in textbooks. The relations obtained show that the relive umbral area and the relative number of small groups are important parameters of the secular variation of solar activity. In particular, they may account for variations in the mean magnetic field in active regions, the complexity of a group according to the magnetic classification, the flare activity of a sunspot group, and its geophysical impact. It is conjectured that the parameter q describes the time-varying relative contribution from the interior and subsurface dynamo mechanisms.