Large scale coherent magnetohydrodynamic oscillations in a sunspot

Area of Science:

• Solar physics
• Plasma astrophysics
• Heliophysics

Background:

• Solar magnetic flux tubes, like harmonic oscillators, theoretically support multiple resonant modes.
• Simultaneous excitation of several resonant modes has not been previously observed in sunspots, especially large ones.

Purpose of the Study:

• To report the detection of the largest-scale coherent oscillations observed in a sunspot.
• To characterize the spectral properties of these oscillations and compare them to global solar acoustic oscillations.
• To investigate the excitation of coherent oscillations in large-scale magnetic structures in the solar atmosphere.

Main Methods:

• Observational astronomy: Detection of large-scale coherent oscillations in a sunspot.
• Spectral analysis: Characterization of oscillation modes and comparison with solar acoustic oscillations.
• Magnetohydrodynamic (MHD) numerical modeling: Validation of observational findings.

Main Results:

• Detection of the largest-scale coherent oscillations observed in a sunspot to date.
• The observed spectrum is significantly different from the Sun's global acoustic oscillations, indicating a superposition of many resonant wave modes.
• Magnetohydrodynamic numerical modeling results agree with the observational data.

Conclusions:

• Demonstrates the excitation of coherent oscillations over spatial scales of 30-40 Mm in extreme magnetic flux regions of the solar atmosphere.
• The findings challenge previous observations and theoretical expectations regarding resonant modes in large sunspots.
• Paves the way for diagnostic applications of these oscillations in solar physics and other astrophysical contexts.