Helicity Injections in Regions of Various Magnetic Fluxes
T.Yamamoto, K.Kusano, T.Yokoyama, and T.Sakurai
In this study, we investigate the amount of magnetic helicity injection
(hereafter, helicity flux)
among active region of various sizes
(having different magnetic fluxes).
We analyzed 78 active regions (more than 600 magnetograms),
using the vector magnetograms obtained with
the Solar Flare Telescope of NAOJ and
SOHO/MDI magnetograms with the method proposed by Kusano et al. (2002).
Ten active regions are tracked for several days,
while other regions are studied based on single-day observation.
The time cadence of data is 96 minutes.
The magnetic flux of these regions ranges from 2.e+12 Wb to 4.e+14 Wb,
and the absolute values of the helicity flux are
from 1.e+17 Wb^2/s to 2.e+22 Wb^2/s.
>From a scatter plot of magnetic flux and helicity flux,
we found that the helicity flux has an upper limit for a given value
of the magnetic flux,
and the upper limit is nealy proportional to the magnetic flux.
We can interpret these results with the model of
helicity injection due to helical turbulence
(Sigma-Effect; Longcope et al. 1998).
Correspondence
Tetsuya Yamamoto (yamamoto@solar.mtk.nao.ac.jp),
Department of Astronomy, Graduate School of Science,
The University of Tokyo
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