A COMBINED STUDY OF PHOTOSPHERIC MAGNETIC AND CURRENT HELICITIES AND SUBSURFACE KINETIC HELICITIES OF SOLAR ACTIVE REGIONS DURING 2006-2013

We compare the average photospheric current helicity H sub(c), photospheric twist parameter alpha (a well-known proxy for the full relative magnetic helicity), and subsurface kinetic helicity H sub(k) for 194 active regions observed between 2006-2013. We use 2440 Hinode photospheric vector magnetogr...

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Bibliographic Details
Published in:The Astrophysical journal 2014-11, Vol.795 (2), p.1-13
Main Authors: Seligman, D, Petrie, G J D, Komm, R
Format: Article
Language:English
Subjects:
APPROXIMATIONS
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
Bias
COMPARATIVE EVALUATIONS
Correlation
CORRELATIONS
Fluid dynamics
Fluid flow
Fluids
HELICITY
MAGNETIC FIELDS
Mathematical analysis
NORTHERN HEMISPHERE
PHOTOSPHERE
SOUTHERN HEMISPHERE
SUN
SURFACES
VARIATIONS
VELOCITY
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Summary:We compare the average photospheric current helicity H sub(c), photospheric twist parameter alpha (a well-known proxy for the full relative magnetic helicity), and subsurface kinetic helicity H sub(k) for 194 active regions observed between 2006-2013. We use 2440 Hinode photospheric vector magnetograms, and the corresponding subsurface fluid velocity data derived from GONG (2006-2012) and Helioseismic and Magnetic Imager (2010-2013) dopplergrams. We find a significant hemispheric bias in all three parameters. The subsurface kinetic helicity is preferentially positive in the southern hemisphere and negative in the northern hemisphere. The photospheric current helicity and the alpha parameter have the same bias for strong fields (|B| > 1000 G) and no significant bias for weak fields (100 G < |B| < 500 G). We find no significant region-by-region correlation between the subsurface kinetic helicity and either the strong-field current helicity or alpha . Subsurface fluid motions of a given handedness correspond to photospheric helicities of both signs in approximately equal numbers. However, common variations appear in annual averages of these quantities over all regions. Furthermore, in a subset of 77 regions, we find significant correlations between the temporal profiles of the subsurface and photospheric helicities. In these cases, the sign of the linear correlation coefficient matches the sign relationship between the helicities, indicating that the photospheric magnetic field twist is sensitive to the twisting motions below the surface.
ISSN:1538-4357
0004-637X
1538-4357
DOI:10.1088/0004-637X/795/2/113