Origin of the Tunguska-1908 Phenomenon B. R. German Institute of Physics of the Ukrainian Academy of Sciences, Donetsk, Ukraine (german@mail.fti.ac.donetsk.ua) Abstract It is generally accepted that the Tunguska explosion resulted from the disruption of cosmic body. Never- theless all data favors a tectonic nature of the event. 1. Introduction On June 30, 1908 a powerful explosion occurred in the Kulik-caldera in Siberia. The blast felled trees in an area over 2150 km 2 . Barometric/seismic dis- turbances and airglows were detected worldwide. 2. Reasons of the Tunguska Event Linisolar tides related to the earthquakes because the important changes in tectonic eruptive behavior occurred usually close to the solstice and equinox periods. First airglows of the Tunguska event began in Europe on 22 June, 1908 and the explosion oc- curred just 8 days after summer solstice. Lunisolar tides have been increased due to the solar eclipse on 28 June, 1908 [1]. It has been proved that a new index M of the solar rotation, defined by integrating the angular momentum density over the whole solar surface, reached a maximum at solar cycle 14: 1901.7-1913.6 (a next maximum at cycle 21 had a relatively small amplitude) [13]. The vortex struc- tures observed on the Sun during the years 1907- 1908 [1] probably reflect an acceleration of surface layers during transport of angular momentum from/ into deeper layers (due to a radial gradient because an equatorial gradient reached a minimum at cycle 14). For the first time solar vortex structures were observed in 1857. On May 5, 1907 the same struc- tures were registered again. A. Stentzel has paid at- tention to a 50-yr period. The inversion of speeds for polarization’s points Arago/Babinet has been noted since 10 May, 1907. Increasing of the angular distance of neutral polarization points, which has begun in May, 1907 proceeded till the end of June, 1908. Exactly after the Tunguska explosion the ma- ximum relative increase of the polarization for the whole period from 1905 till 1910 was recorded [3]. Obviously, this effect could correlate with above mentioned vortex structures. For one day before the Tunguska explosion F. Bush at Arnsberg registered the displacement of polarization minima [3]. It can be explained by the changing in critical frequencies of ionospheric layers Е and F at twilight (pulsations of electric vector of the geofield directed in parallel to a plane of scattering of light reaches a night max- imum earlier, than the stronger perpendicular vec- tor). That is, the nature of depolarization can de- pend on changes in intensity of a geoelectric field. Recently it was proven that the interplanetary mag- netic field (IMF) interacts with the geomagnetic field and causes it to oscillate in resonance with the characteristic of solar g-modes waves [9]. As the Earth moves to the solar rhythm the changes of the geomagnetic field produce small detectable pulsa- tions. It is known that the tangential component of IMF has no compensation, as IMF possesses daily variations with a local peak of intensity nearby 18 h local time. This time coincides with the time of the beginning of pulsations with the period of 3 min registrated by Weber at Kiel on 27-30 June, 1908 [12] (furthermore, although a period of p-mode oscillations of the solar corona is equal to 5 min, a period of pulsations of high layers of the photos- phere is equal to 3 min). Now the data of the Sun- IMF-Earth’s magnetosphere-ionosphere-lithosphere chain are using to predict tectonic events. Because 3-days pulsations at Kiel began before explosion in Siberia and ended in 15 minutes after it we suppose the solar influence as one of the reasons of Tun- guska-earthquake on 30 June, 1908. During the last 100 years an excursions of geomagnetic poles that are possibly connected with processes on the Sun is observed. The assumption about a superimposition of a quadruple field on a main dipole field in the Earth’s core, provides an explanation of the rever- sals of the geomagnetic field [8]. A pole of the Earth’s quadruple momentum is located near Tun- guska area [7]. In Eastern Siberia an agonic (zero declination) line has an anomaly: western declina- tion is observed instead of the eastern one. This line turned clockwise towards the sublatitude orienta- tions from 1900 to 1920. The largest changes were EPSC Abstracts Vol. 5, EPSC2010-430, 2010 European Planetary Science Congress 2010 c  Author(s) 2010