V. Botvinovsky $^{a}$, S. Starchenko $^{b}$
$^{a}$ Institute of Geophysics, Novosibirsk, Russia $^{b}$ Geophysical Observatory "Borok", Borok, Yaroslavl's region, Russia
It can be expected that the azimutal dynamo-currents are concentrated near the boundaries of liquid core of the Earth. A density of current $\bf{J}=\sigma\Bigl{[}\bf{v}\tim\bf{B}\Bigr{]}$ must be close to zero in the most part of liquid core because the magnetic lines are frozen to liquid conductor. Exceptions are the regions near the inner core and mantle where the magnetic lines can not be frozen and have a significant radial component. An estimation of the current density near the core-mantle boundary (CMB) gives $J\approx10^{-1} A m^{-2}$ ($J=\sigma vB$, where $\sigma\approx4\tim10^{5} ohm^{-1} m^{-1}$, $v\approx3\tim10^{-4} m sec^{-1}$, $B\approx8\tim10^{-4} T$ near the CMB). In order to create the real Earth’s magnetic moment a cross section of azimutal currents may be an insignificant part of cross section of liquid core. Similar situation has to take place near the inner core boundary (ICB) except the induction of magnetic field (and current density) must be much more than near the CMB. By methods of optimization built were axis-symmetrical current loop’s models of source of the geomagnetic field. A first type of models consists of two pairs of the loops located at the inner and outer boundaries of liquid core. It’s shown that the currents located near inner core and directed from East to West must create the dominant part of the geomagnetic moment. An unexpected result is that the reverse currents (from West to East) must flow near mantle boundary by two belts located at the latitudes about 30 degrees at the north and south. A second type of models consists of one current loop located at the inner core equator and 21 loops distributed along the mantle boundary. The outer current has the minimums and maximums distributed on the latitude. There are two maximums located at the $\pm30^{o}$. These maximums confirm the necessity of existence of the above reverse currents.