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Test of the Hemisphere Rule of Magnetic Twist in Solar Active Regions Using the Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Data View all abstracts by submitter

Yang Liu   Submitted: 2014-01-25 12:01

Magnetic twist in solar active regions has been found to have a hemispheric preference in sign (hemisphere rule): negative in the northern hemisphere and positive in the southern. The preference reported in previous studies ranges greatly, from sim 58% to 82%. In this study, we examine this hemispheric preference using vector magnetic field data taken by HMI and find that 75% pm 7% of 151 active regions studied obey the hemisphere rule, well within the preference range in previous studies. If the sample is divided into two groups,-,active regions having magnetic twist and writhe of the same sign and having opposite signs,-,the strength of the hemispheric preference differs substantially: ( 64% pm 11% ) for the former group and ( 87% pm 8% ) for the latter. This difference becomes even more significant in a sub-sample of 82 active regions having a simple bipole magnetic configuration: ( 56% pm 16% ) for the active regions having the same signs of twist and writhe, and 93% with lower and upper confidence bounds of 80% and 98% for the active regions having the opposite signs. The error reported here is a 95% confidence interval. This may suggest that, prior to emergence of magnetic tubes, either the sign of twist does not have a hemispheric preference or the twist is relatively weak.

Authors: Y. Liu, J. T. Hoeksema, X. Sun
Projects: SDO-HMI

Publication Status: ApJL accepted
Last Modified: 2014-01-28 12:39
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