NDLI: Active region magnetic fields

Content Provider	Springer Nature Link
Author	Howard, Robert F.
Copyright Year	2000
Abstract	The tilt angles of sunspot groups are defined, using the Mount Wilson data set. It is shown that groups with tilt angles greater than or less than the average value (≈ 5 deg) show different latitude dependences. This effect is also seen in synoptic magnetic field data defining plages. The fraction of the total sunspot group area that is found in the leading spots is discussed as a parameter that can be useful in studying the dynamics of sunspot groups. This parameter is larger for low tilt angles, and small for extreme tilt angles in either direction. The daily variations of sunspot group tilt angles are discussed. The result that sunspot tilt angles tend to rotate toward the average value is reviewed. It is suggested that at some depth, perhaps 50 Mm, there is a flow relative to the surface that results from a rotation rate faster than the surface rate by about 60 m/sec and a meridional drift that is slower than the surface rate by about 5 m/sec. This results in a slanted relative flow at that depth that is in the direction of the average tilt angle and may be responsible for the tendency for sunspot groups (and plages) to rotate their magnetic axes in the direction of the average tilt angle.
Starting Page	119
Ending Page	125
Page Count	7
File Format	PDF
ISSN	02506335
Journal	Journal of Astrophysics and Astronomy
Volume Number	21
Issue Number	3-4
e-ISSN	09737758
Language	English
Publisher	Springer India
Publisher Date	2000-01-01
Publisher Institution	Indian Academy of Sciences
Publisher Place	New Delhi
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	Active regions sunspot groups group tilt angles Astronomy Astrophysics
Content Type	Text
Resource Type	Article
Subject	Astronomy and Astrophysics Space and Planetary Science

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Nature of Tilt Angles of Sunspot Groups During the 22nd Solar Cycle

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