Magneto-acoustic oscillations observed in a solar plage region

TL;DR

This study identifies magneto-acoustic oscillations in a solar plage region, revealing their properties, phase relationships, and potential role in solar atmospheric heating and helioseismology.

Contribution

It provides observational evidence and a theoretical explanation for magneto-acoustic oscillations driven by p-modes in the solar photosphere.

Findings

Magnetic perturbations are associated with 5-minute oscillations.

Perturbation amplitudes correlate with magnetic field strength.

Magnetic perturbations lag Doppler velocity by a quarter cycle.

Abstract

We gave an extensive study for the quasi-periodic perturbations on the time profiles of the line of sight (LOS) magnetic field in 10x10 sub-areas in a solar plage region (corresponds to a facula on the photosphere). The perturbations are found to be associated with enhancement of He I 10830 A absorption in a moss region, which is connected to loops with million-degree plasma. FFT analysis to the perturbations gives a kind of spectrum similar to that of Doppler velocity: a number of discrete periods around 5 minutes. The amplitudes of the magnetic perturbations are found to be proportional to magnetic field strength over these sub-areas. In addition, magnetic perturbations lag behind a quarter of cycle in phase with respect to the p-mode Doppler velocity. We show that the relationships can be well explained with an MHD solution for the magneto-acoustic oscillations in high-\b{eta} plasma. Observational analysis also shows that, for the two regions with the stronger and weaker magnetic field, the perturbations are always anti-phased. All findings show that the magnetic perturbations are actually magneto-acoustic oscillations on the solar surface, the photosphere, powered by p-mode oscillations. The findings may provide a new diagnostic tool for exploring the relationship between magneto-acoustic oscillations and the heating of solar upper atmosphere, as well as their role in helioseismology.