Intermittency spectra of current helicity in solar active regions
Abstract
We analyse the spatial distribution of current helicity in solar active regions. A comparison of current helicity maps derived from three different instruments (Helioseismic and Magnetic 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) is carried out. The comparison showed an excellent correlation between the maps derived from the space-borne 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 intermittency of current helicity, we traditionally use the high-order structure functions 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. SDO/HMI vector magnetograms for three active regions (NOAA 11158, 12494, and 12673) were used to calculate the flatness exponent time variations. All three active regions exhibited emergence of a new magnetic flux during the observational interval. The flatness exponent indicated the increase of intermittency 12-20 hours before the emergence of a new flux. We suppose that this behaviour can indicate subphotospheric fragmentation or distortion of the pre-existed electric current system by emerging magnetic flux.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- November 2018
- DOI:
- 10.1093/mnras/sty2109
- arXiv:
- arXiv:1802.02323
- Bibcode:
- 2018MNRAS.480.3780K
- Keywords:
-
- Sun: magnetic fields;
- Sun: photosphere;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- accepted by MNRAS