Three-minute oscillations above sunspot umbra observed with SDO/AIA and NoRH

TL;DR

This study analyzes three-minute oscillations in sunspot umbrae using simultaneous UV/EUV and radio observations, revealing spatial variations linked to magnetic field inclination.

Contribution

It provides the first detailed analysis of spectral and spatial variations of oscillations across sunspot umbrae using combined high-resolution UV/EUV and radio data.

Findings

Higher frequency oscillations are concentrated near the umbra's center.

Lower frequencies are more prominent at the umbra's periphery.

Variation in oscillation spectrum correlates with magnetic field inclination.

Abstract

Three-minute oscillations over sunspot's umbra in AR 11131 were observed simultaneously in UV/EUV emission by SDO/AIA and in radio emission by Nobeyama Radioheliograph (NoRH). We use 24-hours series of SDO and 8-hours series of NoRH observations to study spectral, spatial and temporal variations of pulsations in the 5-9 mHz frequency range at different layers of the solar atmosphere. High spatial and temporal resolution of SDO/AIA in combination with long-duration observations allowed us to trace the variations of the cut-off frequency and spectrum of oscillations across the umbra. We found that higher frequency oscillations are more pronounced closer to the umbra's center, while the lower frequencies concentrate to the peripheral parts. We interpreted this discovery as a manifestation of variation of the magnetic field inclination across the umbra at the level of temperature-minimum. Possible implications of this interpretation for the diagnostics of sunspot atmospheres is discussed.