Power spectra of velocities and magnetic fields on the solar surface and their dependence on the unsigned magnetic flux density

TL;DR

This study analyzes the power spectra of velocities, magnetic fields, and temperatures on the solar surface, revealing how their distributions depend on magnetic flux density and differ between network and internetwork regions.

Contribution

It provides a detailed spectral analysis of solar surface data, highlighting the relationship between magnetic flux density and the spectral slopes of various physical parameters.

Findings

Magnetic power spectra are broadly distributed with weak peaks at granular and supergranular scales.

Thermal and kinetic spectra are steeper than magnetic spectra at sub-granular scales in internetwork regions.

Spectral slopes of all parameters become similar at high magnetic flux densities (>200 Mx/cm^2).

Abstract

We have performed power spectral analysis of surface temperatures, velocities, and magnetic fields, using spectro-polarimetric data taken with the Hinode Solar Optical Telescope. When we make power spectra in a field-of-view covering the super-granular scale, kinetic and thermal power spectra have a prominent peak at the granular scale while the magnetic power spectra have a broadly distributed power over various spatial scales with weak peaks at both the granular and supergranular scales. To study the power spectra separately in internetwork and network regions, power spectra are derived in small sub-regions extracted from the field-of-view. We examine slopes of the power spectra using power-law indices, and compare them with the unsigned magnetic flux density averaged in the sub-regions. The thermal and kinetic spectra are steeper than the magnetic ones at the sub-granular scale in the internetwork regions, and the power-law indices differ by about 2. The power-law indices of the magnetic power spectra are close to or smaller than -1 at that scale, which suggests the total magnetic energy mainly comes from either the granular scale magnetic structures or both the granular scale and smaller ones contributing evenly. The slopes of the thermal and kinetic power spectra become less steep with increasing unsigned flux density in the network regions. The power-law indices of all the thermal, kinetic, and magnetic power spectra become similar when the unsigned flux density is larger than 200 Mx cm^-2.