HR: 0800h
AN: SH41A-1120    [Abstracts]
TI: Characteristics of the Sun's polar magnetic flux from 1996-2005 using SOHO/MDI observations
AU: * Benevolenskaya, E E
SH41A-1120 AF: Stanford University, W.W. Hansen Experimental Physics Laboratory, Stanford, CA 94305 United States
AU: Hoeksema, J T
SH41A-1120 AF: Stanford University, W.W. Hansen Experimental Physics Laboratory, Stanford, CA 94305 United States
AU: Liu, Y
SH41A-1120 AF: Stanford University, W.W. Hansen Experimental Physics Laboratory, Stanford, CA 94305 United States
AU: Zhao, X
SH41A-1120 AF: Stanford University, W.W. Hansen Experimental Physics Laboratory, Stanford, CA 94305 United States
AU: Scherrer, P H
SH41A-1120 AF: Stanford University, W.W. Hansen Experimental Physics Laboratory, Stanford, CA 94305 United States
AB: We have studied the Sun's polar magnetic field using nearly 10 years of full-disk SOHO/MDI data. We have estimated the time of the polar magnetic field reversals above 78 degrees. The net flux in the southern cap changed polarity in CR 1979 (August, 2001), five rotations later than the north (CR 1974; April, 2001). These are just a little earlier than the times identified by Durrant and Wilson (2003): CR 1981 in the south and CR 1975 in the north. We also investigate apparent solar cycle changes in the total magnetic flux observed in the polar caps. The total flux determination is highly sensitive to changes in random noise due to the different MDI observing modes, to systematic errors in the instrument, and to the exact method of processing the data (e.g. spatial and temporal averaging). This is because nearly all of the flux measurements are near the noise level due to the extreme reduction in the line-of-sight component due to projection effects near the limb. In recent years the SOHO spacecraft has periodically been rotated and this allows us to better characterize the systematic errors. Using observations taken when the inclination of the solar equator provides the best viewing of each pole, we correct for all known errors to provide the best estimate of the solar polar flux with time.
DE: 2162 Solar cycle variations (7536)
DE: 7524 Magnetic fields
DE: 7529 Photosphere
DE: 7536 Solar activity cycle (2162)
SC: SPA-Solar and Heliospheric Physics [SH]
MN: Fall Meeting 2005