1. LONGPERIODICAL OSCILLATIONS OF SOLAR MICROWAVE RADIO EMISSION K.G.Kislyakova 1,2, V.V.Zaitsev 2, A.Riehokainen 3, S.Urpo 3 1 Lobachevsky State University of Nizhni Novgorod 2 Institute of Applied Physics, Russian Academy of Sciences 3 Metsähovi Radio Research Station, Finland Puschino, 2010

2. Main tasks and methods of data processing ● Main tasks of the work: Studying processes in the solar photosphrere, chromosphere and corona, investigation of solar longperiodical microwave emission at 11.7 GHz. We suggest the possible origins explanations of modulations with periods 3-80 min. All data were recorded in 2001 during the Sun observations at 11.7 GHz in Mets ä hovi observatory, Finland ● Data processing methods: Averaging time profile over the 5- 10s interval; Preliminary spectral analysis (PSA) based on the Sliding Window Fourier (SWF) algorithm; ”Cleaning” PSA results: removing trends, noise and spectral components of instrumental origin; Separation of oscillations with periods 3-80 min.

3. Parametric resonance in the Solar Corona ● Frequency of forced oscillations: appr.3 mHz (pumping by the global 5- min oscillations of the photosphere) ● PR can serve as an effective mechanism of coronal plasma heating ● Spectral peculiarities: typical frequencies for PR (pumping frequency, subharmonic, and the first upper frequency), distinctive correlation between intensity and emergence frequency of individual harmonics

4. Sun in UV (304 nm, left panel) and optical (H- alpha) wavelenghts (March 18 2001): (Quit Sun)

5. Initial realisation and spectrum of solar event on March 18 2001 (@11.7GHz)

6. Sun in UV (304 nm, left panel) and optical (H- alpha) wavelenghts (March 29 2001): (Active Sun)

7. Initial realisation and spectrum of solar event on March 29 2001 (@11.7 GHz)

8. Table I

9. Histogram – oscillation occurrence rates This slide illustrates dependence between oscillation occurence rates from its period.

10. A „depthless“ sunspot model ● Sunspot is a sharp coupler of magnetic field, where the gas temperature and pressure are considerably decreased in comparison with surrounding photosphere values. In considered model sunspot is a depthless formation near surface, going into the photosphere till the depth 3-4 thousands km, formed from emerged quasivertical magnetic tube. B – magnetic field,  - Vilson depression, L – depth of bottom magnetic border. Photosphere level is shown by the bold line.

11. Oscillation modes and their characteristic periods Longperiodical oscillations (periods 3-90 min): Twisting mode ( -mode) – returnable rotary motions of the sunspot as a whole object or separate parts of its structure. Radial (r –mode) - quasiperiodic changes of sunspot area or radial distance between its fragments. Daily oscillations (periods from one till some days): Width ( -mode) or Longitude ( -mode) quasiperiodic changes of sunspot absolute geographical coordinates (as a whole object), its width and longitude (connected with active region evolution)

12. Main conclusions: More than 40 events were analyzed, the low-frequency modulation with the periond 3-80 min is discovered in all cases. As a rule, simultaneous modulation of emission with various frequencies is observed. We suggest parametric resonance as one of the possible mechanisms explaining relatively short periodical modulations with the periods about 3, 5 and 10 minutes. The global 5-min oscillations of the solar photosphere play the role of the pumping frequency. The most intensive longperiodical modulations with the periods 20-80 min could be explained as sunspots oscillations, what is in a good coordination with the optical data. The brightness temperature of the flares was determined. Evidences of parametric resonance were discovered not only in the emission from certain ARs, but also in the integral emission of the whole solar disc. The article “Longperiodical oscillations of solar microwave radioemission” representing the results of the work is accepted to the “Astronomicheskij zhurnal”

13. Basic papers: Parametric Resonance in the Solar Corona. Cosmic Research, 2008, Vol. 46, No. 4, pp. 301–308. © Pleiades Publishing, Ltd., 2008. Original Russian Text © V.V. Zaitsev, A.G. Kislyakov, K.G. Kislyakova, 2008, published in Kosmicheskie Issledovaniya, 2008, Vol. 46, No. 4, pp. 310–317. Longperiodical oscillations in the solar active regions: observational evedences. Nagovitsyn Yu.A., Nagovitsyna E.Yu. Proceedings of XIIth International solar physics conference “Solar and Solar-Earth Physics - 2008”, Pulkovo. Quasiperiodical sunspot oscillations on the time scales of decades and hundreds of munites.Nagovitsyn Yu.A., Nagovitsyna E.Yu. Proceedings of XIIth International solar physics conference “Solar and Solar-Earth Physics - 2008”, Pulkovo. Sunspot as a separate structure. A.A. Soloviev, E.A. Kiritsek. Astrophys.bulletin, 2008, band 63, №2, p. 180–192. Gelfreikh G.B., Shibasaki K., Nagovitsyna E.Yu., and Nagovitsyn Yu.A., in Proceedings of IAU Symposium No. 223 Multi-Wavelength Investigations of Solar Activity (St. Petersburg, 2004), p. 525.