Oscillations in the Flaring Active Region NOAA 11272

TL;DR

This study analyzes standing EUV waves during a solar flare in Active Region NOAA 11272, identifying wave periods, magnetic structures, and plasma parameters to understand wave behavior and their relation to magnetic and atmospheric conditions.

Contribution

It provides the first detailed analysis of standing EUV waves in NOAA 11272, combining magnetic field extrapolation and plasma modeling to interpret wave characteristics.

Findings

Identified standing waves with 9- and 19-minute periods in EUV wavelengths.

Mapped the magnetic loops where waves are observed and their disturbed neighbors.

Found that atmospheric densities need to be higher to match observed wave periods.

Abstract

We studied waves seen during the class C1.9 flare that occurred in Active Region NOAA 11272 on SOL2011-08-17. We found standing waves with periods in the 9- and 19-minute band in six extreme ultraviolet (EUV) wavelengths of the SDO/AIA instrument. We succeeded in identifying the magnetic arc where the flare started and two neighbour loops that were disturbed in sequence. The analysed standing waves spatially coincide with these observed EUV loops. To study the wave characteristics along the loops, we extrapolated field lines from the line-of-sight magnetograms using the force-free approximation in the linear regime. We used atmosphere models to determine the mass density and temperature at each height of the loop. Then, we calculated the sound and Alfv{\'e}n speeds using densities $10^8 \lesssim n_i \lesssim 10^{17}$ cm$^{-3}$ and temperatures $10^3 \lesssim T \lesssim 10^7$ K. The brightness asymmetry in the observed standing waves resembles the Alfv{\'e}n speed distribution along the loops, but the atmospheric model we used needs higher densities to explain the observed periods.