Physics
Scientific paper
May 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agusm..sp41c06p&link_type=abstract
American Geophysical Union, Spring Meeting 2001, abstract #SP41C-06
Physics
7524 Magnetic Fields, 7529 Photosphere, 7544 Stellar Interiors And Dynamo Theory
Scientific paper
It has been recently suggested that there is two separate dynamo operating on the Sun. A subphotospheric (e.g. overshoot region) dynamo is responsible for strong magnetic fields of active regions, while the quiet Sun field is generated by the local (surface) dynamo driven by granular flows (Cattaneo 1999). Compelling observational evidence in support of the surface dynamo is still lacking. Because of the small characteristic size and lifetime of granular flows, the Coriolis force has no significant effect on them. Consequently the kinetic helicity of granules will not depend of hemisphere or vary with latitude; it will almost certainly average to zero. Magnetic field generated by such a (non-helical) dynamo should exhibit no hemispheric helicity rule either. In contrast, the sub-photospheric dynamo flows have non-zero kinetic helicity that changes sign across the solar equator. This dynamo will introduce hemispheric asymmetry in magnetic field's twist: positive helicity in southern hemisphere and negative in northern hemisphere. An observed hemispheric helicity rule for active region magnetic fields is well documented (e.g. Pevtsov et al 1995). Thus, the helicity approach can be used to distinguish between sub-photospheric (helical) and surface (non-helical) solar dynamos. Using vector magnetograms from the Advanced Stokes Polarimeter we measure current helicity density α z = Jz / Bz of photospheric field in the quiet Sun at few fixed latitudes. Our results indicate a weak hemispheric asymmetry in distribution of α z with a tendency for averaged helicity to be negative in the northern hemisphere and positive in the southern hemisphere. We interpret this asymmetry in a framework of the sub-photospheric origin of the photospheric field in the quiet Sun.
Longcope Dana Warfield
Pevtsov Alexander
No associations
LandOfFree
Where the Quiet Sun Magnetic Field Comes From? does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Where the Quiet Sun Magnetic Field Comes From?, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Where the Quiet Sun Magnetic Field Comes From? will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1279332