Height distribution of the power of 3-min oscillations over sunspots

TL;DR

This study examines the height distribution of 3-minute oscillations over sunspots and finds that the height inversion effect is common, likely related to magnetic field topology and photospheric level changes.

Contribution

It demonstrates that the height inversion of oscillation power is a widespread feature in sunspots, expanding understanding of their oscillatory behavior.

Findings

Height inversion observed in 9 of 11 sunspots analyzed.

The effect is linked to magnetic field topology.

Possible connection to photospheric level decrease in umbrae.

Abstract

Context. The height structure of 3-min oscillations over sunspots is studied in the context of the recently discovered effect of height inversion: over the umbra, the spatial location of the maximum of chromospheric 3-min oscillation power corresponds to the relative decrease in the power of photospheric oscillations. Aims. We investigate whether the height inversion of the power of 3-min oscillations is a common feature of the spatial structure of the oscillations for the majority of sunspots. Methods. Spectrogram sequences of H-alpha 6563{\AA} and FeI 6569{\AA} over sunspots, acquired with very high cadency (about 2 s or better) are obtained. The distribution of the oscillation power of the line-of-sight velocity signal is studied by using methods of wavelet frequency filtration and Fourier analysis. Results. The effect of the height inversion is found in 9 of 11 analyzed active regions. The interpretation of this effect is possibly connected to both the decrease in the level of photosphere in sunspot umbrae and the magnetic field topology.