Physics of auroral phenomena : proceedings of the 34th Annual seminar, Apatity, 01 - 04 March, 2011 / [ed.: A. G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2011. - 231 с. : ил.

SEA SO NA L V AR IA T IO N S OF DOM INATING ARR IV A L DIRECTIONS OF R EG IST ER ED L IGH T IN G S IG N A L S A S AN INDICATOR OF ANNUAL MOTION OF WORLD THUNDERSTORM CENTER S V.V. Pchelkin1, E.N. Yakushenkov2 1 Polar Geophysical Institute RAS, 26a, Academgorodok St., Apatity, Murmansk region, 184200, Russia 2 Kola department o f Petrozavodsk State University, Apatity, Murmansk region, 184200, Russia Abstract Using measurements of magnetometers in Lovozero observatory (Kola peninsula) for 2006-2009 years, dominant arrival directions of lighting signals were calculated. The average azimuth distributions of registered lighting signals for each season were constructed. Systematic changes in the dominant arrival directions of lighting signals depending on season were found. Estimations of seasonal variability of the activity of the world thunderstorm centers are made. Introduction Irregular spacing of thunderstorm activity centers on the Earth surface (Bliokh et a l, 1980; Rossi et a l, 2001) results in an anisotropy of arrival directions of noise signals in the 6-11 Hz frequency range (near the first Shuman resonance). It might be supposed that variability of position of the thunderstorm centers (and their activity) would be accompanied by seasonal changes of dominant arrival directions of registered lighting signals (Rossi et al, 2007/ The main objective of the given work is the testing of this assumption. Interest of such problem, first of all, consists in check of possibilities of large-scale high-altitude monitoring o f global thunderstorm activity in the given range of frequencies. On the one hand, similar monitoring has not a great accuracy, and it isn’t allowed to calculate the location of an individual lightning (Fullekrug et a l, 1996, 1999; Kemp, 1971; Bliokh et al, 1980;). Many factors bring an essential error in determination of a true bearing on sources of signals (influence of a coastal line, anisotropic conductivity in the ionosphere, magnetic field of the Earth etc.). For example, according with estimations in the paper Fullekrug et al. (1999), the lightning flash bearing (Hollister, California and Silberbom, Germany) exhibits a rotational dependence ~12°, associated with the conductivity contrast between the Earth’s crust and the nearby Pacific Ocean. The bearing deviation exhibit ~11° is attributed to the anisotropic conductivity in the ionosphere during day-and nighttime conditions. Given results demand accuracy of the conclusions and force to base, first of all, on observations of relative variations of the parameters, which were made in approximately identical conditions of wave propagation. On the other hand, existing system o f satellite observations (and ground based observations in VLF region) still do not give the full information about the global distribution of lightning flashes on all Earth surface with the satisfactory time resolution too (Rodger et a l, 2004; Christian et al, 2003). The on-line control of global thunderstorm activity is absent now. Let's notice, that high-latitudes observations are practically free from influence of near thunder-storms. It considerably improves possibilities of large-scale monitoring o f the thunderstorm centers, which grouped mainly in equatorial latitudes. The small number of stations enough removed from each other will allow to execute the parameters fitting of large-scale model of location of lightning flashes on Earth surface. This method demands inexpensive means (in comparison with a satellite observations or VLF lightning location network). In summary we will notice, that feature of monitoring in high latitudes is the proximity to sources of magnetosphere waves. It dictates the necessity of a very careful selection of days without magnetosphere disturbances. Measurements and data processing The data from the regular measurements of the horizontal component of the noise magnetic field at the frequency range of the first Schumann resonance, held at the high-latitude Lovozero observatory for the period 2006-2009, were used. The brief description of the accepting - measuring equipment is contained in papers Roldugin et al. (2003), Beloglazov et al. (2009). The days with the observed disturbances of magnetosphere and technogenic noises, as well as the days with incomplete records were excluded from the experimental data. Thus 300 days (from 3 years) were selected for the analysis. During the processing by the methods of digital filtering the frequency band was narrowed to about the range of 6-11 HZ. Physics o fAuroral Phenomena ", Proc. XXXIV Annual Seminar, Apatity, pp. 193 -196 2011 ^ 7 T \ Po,ar © Kola Science Centre, Russian Academy of Science, 2011 Ш лЩ Geophysical V l / y Institute 193