HR: 1340h
AN: SH13A-1110    [Abstracts]
TI: Testing a possible scenario for delta-spot formation
AU: * MacDonald, R
EM: rkdm@u.washington.edu
AF: University of Washington, University of Washington, Seattle, WA 98195, United States
AU: Fisher, G H
EM: fisher@ssl.berkeley.edu
AF: UC Berkeley, Space Sciences Laboratory # 7450 7 Gauss Way University of California, Berkeley, CA 94720-7450, United States
AU: Leka, K
EM: leka@cora.nwra.com
AF: Northwest Research Associates Colorado Research Associates Division, 3380 Mitchell Ln., Boulder, CO 80301, United States
AB: δ-spot active regions are frequently interpreted as loops of magnetic flux which are strongly twisted. Could these twisted active-region field configurations arise from flux loops that originate from regions of the tachocline (the interface layer between the convection zone and radiative zone) that are strongly sheared by differential rotation? Helioseismic rotation inversions show that the tachocline displays a strong radial shear in the rotation rate at latitudes significantly less than 30 degrees. In addition, they show that the surface variation of differential rotation with latitude persists throughout the convection zone and into the tachocline. In many recent solar cycle dynamo models, most of the magnetic flux participating in the dynamo lies in the tachocline near the base of the solar convection zone. In some of these models, amplification of solar magnetic field from the poloidal (N-S) directions into the toroidal component (E-W direction) occurs primarily from the variation of the solar rotation rate with solar latitude, rather than with depth. In any case, the combination of radial and latitude dependent rotation rate results in shearing motions which may not only stretch magnetic field lines in the tachocline, but may shear them as well, especially at low latitudes. This shearing motion is a potential candidate for generating twisted magnetic field configurations that rise to the photosphere. This leads us to ask the question: Is there a preference for the formation of δ-spot active regions at low latitude? In this poster, we investigate this question observationally, by comparing the latitude distribution of δ-spot active regions with the the distribution of all active regions, most of which do not display strong twist. We show the butterfly diagram of all active regions, just δ-spot regions, and compare and contrast the distribution of the two active region samples with time and latitude. We will use these data to test the hypothesis that δ-spot regions form preferentially at low latitudes, compared to the sample of all active regions.
DE: 7524 Magnetic fields
DE: 7529 Photosphere
DE: 7536 Solar activity cycle (2162)
DE: 7544 Stellar interiors and dynamo theory
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2007 Fall Meeting