POWER SPECTRA OF SOLAR NETWORK AND NON-NETWORK FIELDS

Abstract

We report new properties of solar magnetic fields in a quiet region as found from their magnetic power spectra. The power spectra of network and intranetwork fields (non-network fields) are separately calculated from a Big Bear magnetogram obtained with moderately high spatial resolution of 1.5 arc sec and a high sensitivity reaching 2 Mx cm^-2. The effect of seeing on the power spectrum has been corrected using Fried's (1966) Modulation Transfer Function with the seeing parameter determined in our previous analysis of the magnetogram. As a result, it is found that the two-dimensional power spectra of network and non-network fields appear in a form: Γ($k_0$ ≲ $k$ ≲ $k$ ₁) ∼ $k$ ^-1 and Γ( $k$ ≳ $k$ ₁) ∼ $k$ ^-3.5. Here $k$ ₀ ≈ 0.47 Mm^-1 for network fields and $k$ ₀ ≈ 0.69 Mm^-1 for non-network fields, the latter of which corresponds to the size of mesogranulation; $k$ ₁ ≈ 3.0 Mm^-1 for both, which is about the size of a large granule. The network field spectrum below $k$ ₀ appears nearly flat, whereas that of non-network fields instead decreases towards lower wave numbers as Γ( $k$ ) ∼ $k$ ^1.3. The turnover behavior of magnetic field spectra around $k$ ₁ coincides with that found for the velocity power spectrum, which may justify the kinetic approach taken in previous theoretical studies of the solar magnetic power spectra.