http://arxiv.org/abs/1804.10321
The relation between magnetic and velocity fields in the solar atmosphere is a topic that can now be addressed quantitatively at the statistical level. Here we analyze kinetic energy and cross helicity spectra along with magnetic energy and helicity spectra in two solar active regions using vector magnetograms and Dopplergrams of NOAA~11158 and 12266. Within these active regions, we find similar slopes for kinetic and magnetic energy spectra at intermediate wavenumbers, where the contribution from the granulation velocity has been removed. At wavenumbers around $0.3\Mm^{-1}$, the magnetic helicity is found to be close to its maximal value. The cross helicity spectra are found to be within about 10\% of the maximum possible value. We also develop a two-scale method for cross helicity spectra, which allows us to take the cancellation from the bipolarity of active regions into account. In the quiet Sun, by comparison, the cross helicity spectrum is found to be small.
H. Zhang and A. Brandenburg
Mon, 30 Apr 18
43/63
Comments: 5 pages, 4 figures
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