Observed Effect of Magnetic Fields on the Propagation of Magnetoacoustic Waves in the Lower Solar Atmosphere

TL;DR

This study analyzes how magnetic fields influence magnetoacoustic wave propagation in the lower solar atmosphere using Hinode observations, revealing magnetic suppression of oscillations and changes in wave delay and coherence.

Contribution

It provides new insights into the effects of magnetic fields on wave dynamics and phase relationships in the solar atmosphere based on high-resolution observational data.

Findings

Magnetic fields suppress oscillatory power in the 3-7 mHz band.

Delay time between H-line and G-band decreases with magnetic influence.

A second coherence peak appears in magnetic regions, indicating complex wave behavior.

Abstract

We study Hinode/SOT-FG observations of intensity fluctuations in Ca II H-line and G-band image sequences and their relation to simultaneous and co-spatial magnetic field measurements. We explore the G-band and H-line intensity oscillation spectra both separately and comparatively via their relative phase differences, time delays and cross-coherences. In the non-magnetic situations, both sets of fluctuations show strong oscillatory power in the 3 - 7 mHz band centered at 4.5 mHz, but this is suppressed as magnetic field increases. A relative phase analysis gives a time delay of H-line after G-band of 20\pm1 s in non-magnetic situations implying a mean effective height difference of 140 km. The maximum coherence is at 4 - 7 mHz. Under strong magnetic influence the measured delay time shrinks to 11 s with the peak coherence near 4 mHz. A second coherence maximum appears between 7.5 - 10 mHz. Investigation of the locations of this doubled-frequency coherence locates it in diffuse rings outside photospheric magnetic structures. Some possible interpretations of these results are offered.