Exploring magnetic coupling of solar atmosphere through frequency modulations of 3-min slow magnetoacoustic waves

TL;DR

This study investigates the magnetic coupling in the solar atmosphere by analyzing frequency modulations of 3-minute slow magnetoacoustic waves propagating along fan loops, revealing their driven origin from photospheric oscillations.

Contribution

It introduces the analysis of frequency modulation of 3-minute waves from photosphere to corona, demonstrating their connection and magnetic coupling in the solar atmosphere.

Findings

3-minute waves are periodically modulated with 14-20 min and 24-35 min ranges.

3-minute waves in the corona are driven by photospheric 3-minute oscillations.

Evidence of magnetic coupling through wave propagation along fan loops.

Abstract

Coronal fan loops rooted in sunspot umbra show outward propagating waves with subsonic phase speed and period around 3-min. However, their source region in the lower atmosphere is still ambiguous. We performed multi-wavelength observations of a clean fan loop system rooted in sunspot observed by Interface Region Imaging Spectrograph (IRIS) and Solar Dynamics Observatory (SDO). We utilised less explored property of frequency modulation of these 3-min waves from the photosphere to corona, and found them to be periodic with the ranges in 14-20 min, and 24-35 min. Based on our findings, we interpret that 3-min slow waves observed in the coronal fan loops are driven by 3-min oscillations observed at the photospheric footpoints of these fan loops in the umbral region. We also explored any connection between 3-min and 5-min oscillations observed at the photosphere, and found them to be poorly understood. Results provide clear evidence of magnetic coupling of the solar umbral atmosphere through propagation of 3-min waves along the fan loops at different atmospheric heights.