Study of Waveguides and Resonant Cavities over Sunspot Volumes Using Multichannel Solar Dynamics Observatory Observations

Abstract For the first time, we have determined the spatial distribution of magnetic waveguides and resonant cavities at different heights of sunspot atmosphere. We analyzed the time series of EUV/UV images observed by the Solar Dynamics Observatory in the different temperature channels. We have decomposed these images into narrowband oscillating components, interpreted as wave sources. The methods of pixelized wavelet filtering and oscillation mode decomposition were used. For all studied sunspots, the presence of selected bands in the spectra was shown. Each band corresponds to oscillations forming spatial waveguides in the volume of the sunspot atmosphere. The formation of waveguide bundles in the height from photospheric to coronal levels is shown. The regions of the waveguides with maximum oscillating power, where resonant cavities are formed, are identified. Their detection is an experimental proof of the theory of resonant layers, previously proposed to explain the presence of significant harmonics in the oscillation spectrum. The different shapes of the cavities reflect the structure of the magnetic tubes along which the waves propagate. The distribution of sources in the height layers indicates the influence of the wave cutoff frequency caused by the inclinations of the magnetic field lines. We discuss the possibility of upward wave transport due to periodic amplification of the oscillating power in the detected cavities.