Scattering of the f-mode by small magnetic flux elements from observations and numerical simulations

TL;DR

This study combines numerical simulations and observations to analyze how small magnetic flux elements scatter f-modes in the solar atmosphere, revealing the dependence of scattering characteristics on magnetic flux and flux tube properties.

Contribution

It introduces detailed 3D simulations of f-mode scattering by magnetic flux tubes and compares results with high-resolution solar observations, enhancing understanding of wave-magnetic interactions.

Findings

Scattered wave amplitude scales with magnetic flux.

Jacket modes carry 40% of energy compared to tube modes.

Simulated phase shifts match observed dependence on wavenumber.

Abstract

The scattering of f-modes by magnetic tubes is analyzed using three-dimensional numerical simulations. An f-mode wave packet is propagated through a solar atmosphere embedded with three different flux tube models which differ in radius and total magnetic flux. A quiet Sun simulation without a tube present is also performed as a reference. Waves are excited inside the flux tube and propagate along the field lines, and jacket modes are generated in the surroundings of the flux tube, carrying 40% as much energy as the tube modes. The resulting scattered wave is mainly an f-mode composed of a mixture of m=0 and m=+/-1 modes. The amplitude of the scattered wave approximately scales with the magnetic flux. A small amount of power is scattered into the p_1-mode. We have evaluated the absorption and phase shift from a Fourier-Hankel decomposition of the photospheric vertical velocities. They are compared with the results obtained from the emsemble average of 3400 small magnetic elements observed in high-resolution MDI Doppler datacubes. The comparison shows that the observed dependence of the phase shift with wavenumber can be matched reasonably well with the simulated flux tube model. The observed variation of the phase-shifts with the azimuthal order $m$ appears to depend on details of the ensemble averaging, including possible motions of the magnetic elements and asymmetrically shaped elements.