Long quasi-periodic oscillations of sunspots and nearby magnetic structures

¹ University of Turku, 20014 Turku, Finland
e-mail: vvsvid.smirnova@yandex.ru
² Central (Pulkovo) Astronomical Observatory, Russian Academy of Sciences, 196140 Saint Petersburg, Russia
³ Sobolev Astronomical Institute, Saint Petersburg State University, 198504 Saint Petersburg, Russia
⁴ Aalto University, Metsähovi Radio Observatory, 02540 Kylmälä, Finland
⁵ Bauman Moscow State Technical University, 105005 Moscow, Russia

Received: 15 May 2012
Accepted: 8 February 2013

Abstract

Aims. Simultaneous study of long quasi-periodic oscillations in sunspots (using line-of-sight magnetic field data) and nearby magnetic structures located above them (using radio emission data at 37 GHz) was the basic aim of this work.

Methods. Data from the ground-based radio-telescope (Metsähovi Radio Observatory, Aalto University, Finland) and the Helioseismic and Magnetic Imager instrument on-board the Solar Dynamics Observatory spacecraft were obtained and analyzed. We used the wavelet (Morlet) analysis and the fast Fourier transform (FFT) method to obtain the oscillation periods.

Results. Long-period oscillations in intervals of 200–400 min were found both in radio and in magnetic field data. The interpretation of these oscillations and their propagation to higher levels of the solar atmosphere are discussed in the context of a “shallow sunspot” model.