Long-period oscillations of sunspots and small-scale magnetic structures
Introduction Solar oscillatory phenomenon has been observed in different solar structures (sunspots, pores (photosphere), coronal loops, faculae) by ground-based and cosmic instruments (for example, see: Kobrin et al. 1976, Ofman 2000, Loukitcheva et al. 2005, Dorotovic et al. 2008, Foullon et al. 2004, 2009, Yuan et al. 2011). A significant number of reports have been devoted to short-period oscillations (3-5 minutes) of sunspots. These oscillations are interpreted as the propagation of acoustic, slow or fast MHD waves (Nakariakov 2007, Bogdan 2000, Bogdan et al. 2003, Parchevsky & Kosovichev 2009, Felipe et al. 2010, Zhugzhda 2008). Long quasi-periodic oscillations (30 minutes - several hours) of sunspots have been studied considerably less than the 3-5 minutes oscillations (Efremov et al., 2015). The mechanism responsible for the generation of such long periods in sunspots is under discussion. Long quasi-periodic oscillations with periods of 20-40, 60-100 minutes, were also detected above sunspots at radio waves (microwave range, Gelfreikh et al. 2006, Chorley et al. 2010, 2011; Abramov-Maximov et al. 2013, 2018, 2019). The question is: what is the nature of long-period components in the oscillatory spectrum of sunspots (and radio source above sunspots)? Introduction More interesting – long quasi-periodic oscillations of small-scale solar magnetic structures (facular knots). Recently proposed by Kolotkov et al. 2017 and Riehokainen et al. 2019. Periods: 80-250 minutes. No analytical interpretation. This study represents the results of: 1. the investigation of long quasi-periodic oscillations of sunspots using observational data obtained at radio waves (ground-based observations at 37 GHz) and data obtained from the observations of the line-of-sight component of the magnetic field (Solar Dynamics Observatory (SDO) spacecraft); 2. the investigation of long quasi-periodic oscillations of facular knots by using magnetic field data, UV lines, continuum (SDO).
