Vector magnetic fields, subsurface stresses and evolution of magnetic helicity |
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| Authors: | Richard Canfield Alexei Pevtsov |
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| Institution: | (1) Department of Physics, Montana State University, 59717-3840 Bozeman, Montana |
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| Abstract: | Observations of the strength and spatial distribution of vector magnetic fields in active regions have revealed several fundamental
properties of the twist of their magnetic fields. First, the handedness of this twist obeys a hemispheric rule: left-handed
in the northern hemisphere, right-handed in the southern. Second, the rule is weak; active regions often disobey it. It is
statistically valid only in a large ensemble. Third, the rule itself, and the amplitude of the scatter about the rule, are
quantitatively consistent with twisting of fields by turbulence as flux tubes buoy up through the convection zone. Fourth,
there is considerable spatial variation of twist within active regions. However, relaxation to a linear force-free state,
which has been documented amply in laboratory plasmas, is not observed. |
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| Keywords: | Magnetic fields currents magnetic helicity |
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