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.