Journal Article

A new dynamo pattern revealed by solar helical magnetic fields

Hongqi Zhang, T. Sakurai, A. Pevtsov, Yu Gao, Haiqing Xu, D. D. Sokoloff and K. Kuzanyan

in Monthly Notices of the Royal Astronomical Society: Letters

Published on behalf of The Royal Astronomical Society

Volume 402, issue 1, pages L30-L33
Published in print February 2010 |
Published online February 2010 | e-ISSN: 1745-3933 | DOI: http://dx.doi.org/10.1111/j.1745-3933.2009.00793.x

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Abstract

A previously unobservable mirror asymmetry of the solar magnetic field – a key ingredient of the dynamo mechanism which is believed to drive the 11-year activity cycle – has recently been measured. This was achieved through systematic monitoring of solar active regions carried out for more than 20 years at observatories in Mees, Huairou and Mitaka. In this Letter we report on detailed analysis of vector magnetic field data, obtained at Huairou Solar Observing Station in China. Electric current helicity (the product of current and magnetic field components in the same direction) was estimated from the data and a latitude–time plot of solar helicity during the last two solar cycles has been produced. We find that like sunspots helicity patterns propagate equatorwards, but unlike sunspot polarity helicity in each solar hemisphere does not change sign from cycle to cycle, thus confirming the theory. There are, however, two significant time–latitudinal domains in each cycle when the sign briefly inverts. Our findings shed new light on stellar and planetary dynamos and are yet to be included in the theory.

Keywords: Sun: activity; Sun: magnetic fields

Journal Article.  2881 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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