Observations of Magnetic Field Changes in Active Regions
نویسندگان
چکیده
منابع مشابه
Helical Magnetic Fields in Solar Active Regions: Theory vs. Observations
The mean value of the normalized current helicity αp = B · (∇×B)/B 2 in solar active regions is on the order of 10 m, negative in the northern hemisphere, positive in the southern hemisphere. Observations indicate that this helicity has a subsurface origin. Possible mechanisms leading to a twist of this amplitude in magnetic flux tubes include the solar dynamo, convective buffeting of rising fl...
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Recent observational evidence for magnetic field direction effects on helioseismic signals in sunspot penumbrae is suggestive of magnetohydrodynamic (MHD) mode conversion occurring at lower levels. This possibility is explored using wave mechanical and ray theory in a model of the Sun’s surface layers permeated by uniform inclined magnetic field. It is found that fastto-slow conversion near the...
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Active regions can be used as a diagnostic of the sub-photo-spheric activity. In this review I will discuss how the physical conditions in the subsurface layers of the Sun form and modify the three dimensional complex of the active region. Many characteristics of active regions are related to the conditions under which magnetic ux tubes are generated and to their evolution as they rise in the s...
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The classical concept of extrapolating the photospheric magnetic field from line-of-sight measurements B` assuming a pure force-free field is revisited and a new procedure is proposed which is based on: 1) non-vanishing magnetic forces, 2) known horizontal forces from direct measurement of pressure or a related quantity (continuum brightness), 3) a small perturbation to the potential or linear ...
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The purpose of this letter is to address a blind-spot in our knowledge of solar active region statistics. To the best of our knowledge there are no published results showing the variation of the Mount Wilson magnetic classifications as a function of solar cycle based on modern observations. We show statistics for all active regions reported in the daily Solar Region Summary from 1992 January 1 ...
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ژورنال
عنوان ژورنال: Symposium - International Astronomical Union
سال: 1971
ISSN: 0074-1809
DOI: 10.1017/s0074180900022877