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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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 ...
متن کاملOn the Force-Freeness of Photospheric Magnetic Fields in Solar Active Regions: The Current Density Method
We introduce and apply a method to investigate the force-free character of the photospheric magnetic fields in solar active regions. The vertical current density, inferred from vector magnetograms, is decomposed into a helical (assumed field-aligned) component, and a component perpendicular to the magnetic field. Contrary to the classical method of calculating the integrated Lorentz forces, the...
متن کاملVertical Lorentz Force and Cross-field Currents in the Photospheric Magnetic Fields of Solar Active Regions
We demonstrate that the vertical Lorentz force and a corresponding lower limit of the cross-field electric current density can be calculated from vector magnetograms of solar active regions obtained at a single height in the solar atmosphere, provided that the vertical gradient of the magnetic field strength is known at this height. We use a predicted vertical magnetic field gradient derived fr...
متن کاملConsistent determination of quasi force-free magnetic fields from observations in solar active regions
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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ژورنال
عنوان ژورنال: Proceedings of the International Astronomical Union
سال: 2004
ISSN: 1743-9213,1743-9221
DOI: 10.1017/s1743921304005034