Physics of auroral phenomena : proceedings of the 36th Annual seminar, Apatity, 26 February – 01 March, 2013 / [ed. board: A. G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2013. - 215 с. : ил., табл.

IDENTIFICATION OF LONG-PERIOD MHD FLUCTUATIONS IN THE MAGNETOSPHERE AS PRECURSORS OF FLARES BYMETHODS OF WAVELET AND SKELETON ANALYSIS S.E. Revunov, D.V. Shadrukov, N.V. Kosolapova (Nizhniy Novgorod State Pedagogical University, Nizhniy Novgorod, Russia) 1. Introduction It was observed earlier [Bystrov et al, 1979] that a few days before the expansion of a Solar flare can be observed long-period (20 minutes or more) geomagnetic pulsations in the components of the geomagnetic field o f ground- based observatories. In [Smirnova, 2010] showed that indeed for 2-3 days before the Solar flare enhancement of long-period pulsations of H-component of the geomagnetic field in comparison with quiet periods is observed. There is also pointed out that the correlation coefficient of the spectral density o f X-ray radiation and the horizontal component of the magnetic field can reach 93%. This allowed the claim on the effect of the spectral composition of ionizing radiation from the Sun to pre-flare spectrum of growing geomagnetic fluctuations. Unfortunately, this conclusion on the consideration of a narrow range of oscillation periods for one event o f extreme flare is based. In addition calculated the correlation coefficient is not accurately set moments of synchronization of processes on terrestrial observatories. A major factor limiting consideration of direct communication fluctuations o f Solar ionizing radiation and geomagnetic pulsations is the inertia of the ionosphere [Barkhatov et al., 2004] is observed. In our study using large experimental data, which includes data from 20 extreme X-ray flares is performed by wavelet analysis of geomagnetic pulsations at different scales within a five-day interval before each flare. Feature of the data is the use of wavelet-skeleton technology allows maximum eliminate uncertainty in the interpretation of results. The study aims to establish the possibility o f using evidence obtained synchronization skeletons as precursors of a powerful Solar flares. It is necessary to test the hypothesis o f the electromagnetic impact of Solar radiation on the physical processes in the Earth's magnetosphere. The study was performed with minute data for the horizontal component of the geomagnetic field of six observatories Leirvogur, Valentia, Kanoya, Hatizyo, Kakioka, Memambetsu in a wide range of coordinates (latitude geom. 31°-64°) derived from the resource http://wdc.kugi.kyoto-u.ac.jp. Were analyzed in simultaneous minute data about the power of X-rays and the data on the Solar wind - the flow velocity, density, the magnitude o f the IMF granted resource http://spidr.ngdc.noaa.gov/spidr. The study of each case included a flare interval of observations containing 4.5 days (6480 min) before register the flare and 0.3 days (500 minutes) after register. Thus, each analyzed interval contains 6980 minutes of simultaneous observations of the geomagnetic field, parameters of the solar wind and the power of X-rays. The main criteria for the selection of such events was magnetically quiet environment for the entire five-day observation period (|Dst|<20nT) and analyzed all flares have been attributed to the extreme power class X (W> 10-4 W/m2). According to these criteria, 20 flares were analyzed according to the catalog http://vso.nso.edu/cgi/catalogui. The date of the analyzed flares o f class X: 07.09.2005, 16.07.2004, 02.11.2003, 28.10.2003, 19.10.2001, 23.07.2002, 13.12.2001, 17.03.2003, 26.02.2004, 07.11.2004, 24.09.2001, 03.08.2002, 06.04.2001, 28.12.2001, 21.04.2002, 31.10.2002, 09.06.2003, 15.06.2003,13.08.2004, 30.10.2004. 2. Selection tool for spectral analysis The task of registering pulsations at a certain frequency in the horizontal component of the geomagnetic field can generally be reduced to the construction of the dynamic amplitude and frequency of the Fourier spectrum of the magnetogram with each participating in the experiment observatory. However, this approach does not allow to say exactly at what point in time there was of interest to us harmonica in the analyzed signal. This is due to the fact that the Fourier transformation algorithm operates with infinite harmonic functions, which leads the result of using, or to a good localization of the wide frequency band in time or for good specificity narrow bandwidth indefinitely in a wide time interval. As a result of the registration of interest to us, the harmonics can be determined with great inaccuracy. In addition, we have set our task need to check the fact of registration of the same type of long-period harmonics on all the analyzed stations at a specific time in the presence of a quantitative objective calculation of the consistency of the spectra obtained. Such study may be performed under an alternative approach to the spectral signal processing - wavelet transform. Its advantage in the first definition of the basis decomposition of the analyzed signal in the form of a finite function which selected for a specific numerical experiment is provided. Secondly, wavelet analysis allows to obtain the spectrum at a specific frequency band at a particular time interval, which makes it possible to limit the search features of the original signal. Third, the use of post-processing technique results of wavelet analysis to *Physics o fAuroral Phenomena”, Proc. XXXVI Annual Seminar, Apatity, pp. 55 - 58, 2013 © Kola Science Centre, Russian Academy of Science, 2013 55 Polar Geophysical Institute