Magnetic Helicity Generation Inside the Sun
Abstract
Magnetic helicity may be inferred from several types of observation including filament morphology and vector magnetograms of the photospheric magnetic fields. The latter of these which are the most quantitative clearly reveal an anti-correlation between solar latitude and active-region twist; field is preferentially left-handed in the North. A key feature of this hemispheric trend is that one-quarter to one-third of all regions violate it. Separate observations suggest that the helicity of an active region reflects to some degree the twist in the magnetic field below it. One mechanism by which rising magnetic flux tubes can become twisted the Sigma-effect predicts handedness amplitudes and levels of statistical variation consistent with observation. This mechanism does not generate helicity rather it produces twist and writhe of opposite signs of which only the twist is reflected in the coronal field. A separate model calculation predicts that during the emergence of an active region coronal twist will increase from zero over several days as helicity propagates along the flux tube. Recent observations by Pevtsov et al. corroborate this predicted time history lending support to the hypothesis that coronal helicity originates below the solar surface.
- Publication:
-
IAU Joint Discussion
- Pub Date:
- 2003
- Bibcode:
- 2003IAUJD...3E..26L