http://arxiv.org/abs/1802.02323
We intend to analyse the intermittency spectra of current helicity in solar active regions. We made a pixel-by-pixel comparison of current helicity maps derived from three different instruments, namely by Helioseismic and Magnetc Imager on board the Solar Dynamics Observatory (SDO/HMI), Spectro-Polarimeter on board the Hinode, and Solar Magnetic Field Telescope at the Huairou Solar Observing Station, China (HSOS/SMFT). The comparison showed an excellent correlation between the maps derived from the spaceborne instruments and moderate correlation between the maps derived from SDO/HMI and HSOS/SMFT vector magnetograms. The results suggest that the obtained maps characterize real spatial distribution of current helicity over an active region. To analyse the multifractality and intermittency of current helicity, we traditionally use the high-order structure function and flatness function approach. The slope of a flatness function within some range of scales – the flatness exponent – is a measure of the degree of intermittency. We used SDO/HMI vector magnetograms to calculate the flatness exponent variations of current helicity of three active regions: NOAA 11158, 12494, and 12673. The flatness exponents were determined within the scale range of 2-10 Mm. All three regions exhibited emergence of a new magnetic flux during the observational interval. Interestingly, the flatness exponent increased rapidly 12-20 hours before the emergence of a new flux and restored its previous value by the beginning of the emergence. We suppose that this behaviour can be explained by subphotospheric fragmentation or distortion of the existed current system by emerging magnetic flux. During the imperturbable development of active region, the flatness exponent of current helicity remains relatively low and the intermittency range shifts toward higher values up to 20-40 Mm.
A. Kutsenko, V. Abramenko, K. Kuzanyan, et. al.
Thu, 8 Feb 18
7/43
Comments: N/A