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Helicity Observation of Weak and Strong Fields View all abstracts by submitter

Mei Zhang   Submitted: 2006-06-09 07:38

We report in this letter our analysis of a large sample of photospheric vector magnetic field measurements. Our sample consists of 17200 vector magnetograms obtained from January 1997 to August 2004 by Huairou Solar Observing Station of the Chinese National Astronomical Observatory. Two physical quantities, α and current helicity, are calculated and their signs and amplitudes are studied in a search for solar cycle variations. Different from other studies of the same type, we calculate these quantities for weak (100G<|B_z|<500G) and strong (|B_z|>1000G) fields separately. For weak fields, we find that the signs of both α and current helicity are consistent with the established hemispheric rule during most years of the solar cycle and their magnitudes show a rough tendency of decreasing with the development of solar cycle. Analysis of strong fields gives an interesting result: Both α and current helicity present a sign opposite to that of weak fields. Implications of these observations on dynamo theory and helicity production are also briefly discussed.

Authors: Mei Zhang
Projects: None

Publication Status: accepted for publication in ApJ Letter
Last Modified: 2006-09-18 17:53
Go to main E-Print page  Photospheric Magnetic Field Properties of Flaring Versus Flare-Quiet Active Regions. III. Magnetic Charge Topology Models  MHD waves in magnetically twisted flux tubes in twisted magnetic environment  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

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