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.

DETECTION OF MAGNETOGRAVITY WAVES BY IONOSPHERIC F2 LAYER DATA AND MAGNETIC OBSERVATIONS DURING HIGH ENERGY GEOPHYSICAL EVENT O.M. Barkhatova ''2, N.V. Kosolapova 1,2 1Nizhny Novgorod State University o fArchitecture and Civil Engineering (NNGASU), Nizhny Novgorod, Russia Nizhniy Novgorod State Pedagogical University (Minin University), Nizhniy Novgorod, Russia Abstract The appearance o f magnetogravity waves (MGW) during development of two strong (over 6.5 on the Richter scale) earthquakes on the west coast of Indonesia and Turkey is revealed. For this aim the simultaneous disturbances of ionospheric layers F2, E, Es concentration and disturbances of geomagnetic field components are analyzed. The observed magnetogravitational activity was growing at two days before the earthquakes and two days after them. During the days o f earthquakes MGW were not observed but it was noted the passage of acoustic-gravity waves. The possibility o f MGW existence in the equatorial ionosphere has been confirmed by analysis of the corresponding dispersion relations. These relations were obtained on the base of magnetohydrodynamical equations for finite conductivity ionospheric space. Introduction The disturbances o f ionospheric layers ionization are often associated with wave phenomena accompanying high energy geophysical events (earthquakes, tsunamis , the instability of the auroral electrojet, etc.). In recent work the questions o f wave disturbances generation and transfer in the ionosphere are mainly restricted by the different spatial scales acoustic-gravity waves (AGW) [Носке et al., 1996; Vlasov et al., 2011]. However the existence of ionized component in the atmosphere creates the conditions for slow magnetohydrodynamic (MHD) waves propagation in this space which contains geomagnetic disturbances. The consideration of combined magnetic field and gravity influence causes to possibility of so-called magnetogravity waves (MGW) propagation in the ionosphere which velocities is higher than AGW but lower than MHD [Sorokin and Fedorovich, 1982; Barkhatova et al., 2009; Barkhatova et al, 2012]. The magnetic disturbance strengthening may be caused by Cherenkov electron flow radiation from the source of future earthquake. This flow creates magnetic disturbances on the way from the source to ionosphere. In this case the duration o f magnetic disturbances and their intensity determine the magnitude of a future earthquake [Akhundov et al., 2004; Guseinov et al., 2001]. Because of high conductivity of ionospheric plasma at F2 layer altitudes, such magnetic field disturbances associated with earthquake preparation can cause fluctuations of ionospheric plasma and in presence o f gravity excite magnetogravitational activity. In this paper the possibility o f MGW formation from high-energy source (earthquake) in the middle- and low- latitude ionosphere is studied. For this aim the search of MGW is revealed on the base of simultaneous observations of the layers F2, E and Es concentration variations and magnetic observations during two strong earthquakes on the west coast o f Indonesia and in Turkey with magnitude of at least 6.5 on the Richter scale. The possibility of MGW existence at height o f ionospheric layer F2 the equatorial region is analytically performed under the condition of perpendicular direction of gravity force and geomagnetic field. Obtained dispersion relations of MGW propagating modes allow us to determine their specific parameters and compare them with the experimental observations. The experimental data selection and processing The data o f ionospheric layers Es, E and F2 critical frequencies and geomagnetic field X, Y, Z components variations are analyzed in a period o f two underground earthquakes July 17, 2006 and January 8 , 2006. The time resolution o f used data was 15 minutes. Coordinates o f earthquake epicenter, time o f earthquake start and parameters o f selected stations are shown in Table 1. Epicentral distance to the stations did not exceed 1500 km. The MGW search was performed within a time interval containing 3 days before the event, the day of event, and 3 days after them. The level o f global geomagnetic activity during the study period was estimated from the planetary index Kp values. To avoid geomagnetic field disturbances which are not related to MGW propagation, the X, Y, Z component values for all considered stations have been cleared from the effects caused by ring current symmetric and asymmetric parts. To estimation of ionospheric disturbance level which is not related with periodic variations, Physics o f Auroral Phenomena”, Proc. XXXVI A nnual Seminar, Apatity, pp. 139 - 142, 2013 f 7 f \ P o la r © Kola Science Centre, Russian Academy of Science, 2013 u i / U j Geophysical \u_y Institute 139