Modelling magnetic helicity flux through solar photosphere from ASO-S/FMG

Magnetic helicity is a key geometrical parameter to describe the structure and evolution of
solar coronal magnetic fields. The accumulation of magnetic helicity is correlated with the
nonpotential magnetic field energy, which is released in the solar eruptions. Moreover, the
relative magnetic helicity fluxes can be estimated only relying on the line-of-sight magnetic
field (e.g. Démoulin and Berger 2003). The payload Full-disk MagnetoGraph (FMG) on the
Advanced Space-based Solar Observatory (ASO-S) currently has been supplying the con-
tinuous evolution of line-of-sight magnetograms for the solar active regions, which can be
used to estimate the magnetic helicity flux. In this study, we use eight-hour line-of-sight
magnetograms of NOAA 13273, at which the Sun–Earth direction speed of the satellite is
zero to avoid the oscillation of the magnetic field caused by the Doppler effect on polar-
ization measurements. We obtain the helicity flux by applying fast Fourier transform (FFT)
and local correlation tracking (LCT) methods to obtain the horizontal vector potential field
and the motions of the line-of-sight polarities. We also compare the helicity flux derived
using data from the Heliosesmic and Magnetic Imager (HMI) on board the Solar Dynamics
Observatory (SDO) and the same method. It is found that the flux has the same sign and the
correlation between measurements is 0.98. The difference of the absolute magnetic helicity
normalized to the magnetic flux is less than 4%. This comparison demonstrates the reliabil-
ity of ASO-S/FMG data and that it can be reliably used in future studies.