Open AccessComparison of photospheric current helicity and subsurface kinetic helicity
Author(s) -
Gao Yu,
Zhang Hongqi,
Zhao Junwei
Publication year - 2009
Publication title -
monthly notices of the royal astronomical society: letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.067
H-Index - 122
eISSN - 1745-3933
pISSN - 1745-3925
DOI - 10.1111/j.1745-3933.2008.00615.x
Subject(s) - helicity , sign (mathematics) , kinetic energy , physics , current (fluid) , surface (topology) , amplitude , geometry , optics , particle physics , classical mechanics , mathematics , thermodynamics , mathematical analysis
We make a comparison between photospheric current helicity and subsurface kinetic helicity in solar active regions. Four parameters are employed: average value of vertical component of current helicity density 〈 B z · (∇× B ) z 〉 (〈 H c 〉 ), average force‐free field factor and mean subsurface kinetic helicity 〈 v · (∇× v )/| v | 2 〉 (α v ), which is denoted as two different parameters, 〈α v 1 〉 and 〈α v 2 〉 , according to different depths beneath the solar surface. A total of 38 active regions are investigated. The results show that the signs of 〈 H c 〉 and α ave have a typical hemispheric distribution feature. In contrast, the sign of 〈α v 1 〉 presents the opposite feature to the above two parameters. For 〈α v 2 〉 , there is no obvious preponderance of the sign in each hemisphere as with the other three parameters. Although there is an opposite hemispheric preponderance between the signs of current helicity and that of kinetic helicity at 0–3 Mm beneath the solar surface, the uncertain correlations between 〈 H c 〉 and 〈α v 1 〉, α ave and 〈α v 1 〉, 〈 H c 〉 and 〈α v 2 〉, and α ave and 〈α v 2 〉 (the correlation coefficients are −0.095, 0.118, −0.102 and −0.179, respectively) do not support that the photospheric current helicity has a cause and effect relation with the kinetic helicity at 0–12 Mm beneath the solar surface.