NEAR-EARTH EFFECTS OF THE INTERPLANETARY MAGNETIC FIELD
V. I. Odintsov (1), A. N. Zaitzev (1)
(1) Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Russian Academy of Sciences, Troitsk, Moscow region, 142190, Russia
The questions related to the action of the interplanetary magnetic field (IMF) sector structure changes on the ground-level geomagnetic field variations are discussed in this paper. In the sixties Svalgaard and Mansurov discovered that the shape of diurnal variations of a magnetic field in high latitudes depend on the sign of IMF sector structure. Later this dependence was named as Svalgaard-Mansurov effect. We use the technique based on the Svalgaard-Mansurov effect for the sector structure sign definition. For that we use the data of Vostok Antarctic Station (Russia) and Resolute Bay Observatory (Canada) placed in southern and northern hemispheres accordingly. It allows us to avoid the seasonal effect that handicaps the definition of the sector structure sign in equinox and summer seasons. Now we have continued the computation of the sector structure signs interrupted about ten years ago. The table of IMF sector signs for last decade is presented in the report. A comparison of sector signs obtained from ground-level observations with the direct satellite measurements of IMF has shown their rather good coincidence. It is especially important, that the direct satellite measurements of an interplanetary magnetic field have begun much later than ground-level measurements. The discussed method allows us to fill the missing data in the direct satellite measurements and to prolong the series of observations of an interplanetary magnetic field to those years, when the direct measurements were not yet conducted. The attempt was done to compare the spectral features of geomagnetic variations with IMF sector signs changes. On the charts of spectral - time responses of geomagnetic variations it is possible to infer rather evident the moments of transition of the Earth from the one sign of sector structure to the another. We have developed a method of an adaptive filtration that has allowed us to determine the boundaries of transition between sectors as the result of processing data for both middle- and low-latitude observatories. The results of definition of IMF sector structure according the geomagnetic field measurements for more than 40-year's period are presented in the Internet http://www.izmiran.rssi.ru.
The work is supported by the Russian Fund of Basic Researches, RFBR grant 00-07-90206.