HEMISPHERICAL AND LATITUDINAL DIFFERENCES IN THE RESPONSE OF GEOMAGNETIC-ACTIVITY TO RECURRENT SOLAR-WIND STREAMS

The data-adaptive technique of Singular Spectrum Analysis isolates sig nificant signal components from background noise in a time series. Thi s methodology is adopted for analysis of indices of geomagnetic activi ty, interplanetary magnetic field (IMF) and solar wind parameters duri ng an interval in 1974 marked by strong recurrent solar wind streams t o bring out the latitudinal dependence and differences in the geomagne tic response between the northern and the southern hemispheres. The ge oeffectiveness of the azimuthal component of IMF in the observed 28-da y periodicity at low latitudes can be attributed to the seasonally dep endent IMF polarity influence through the Russell-McPherron mechanism. In respect of the 14-day oscillation, the solar wind velocity, the va riability and density which characterize the recurrent streams appear significant in their efficacy at subauroral and auroral latitudes as a lso in generating North-South asymmetry in the geomagnetic response. A clear difference in the response to recurrent solar wind streams, bet ween the two hemispheres, is brought out with the southern (northern) hemisphere showing greater activity with similar to 14-d (similar to 2 8-d) periodicity. The observed responses can be interpreted in terms o f the geomagnetic changes associated with the sector structure and sec tor boundary of IMF through the Russell-McPherron (R-M) effect. (C) 19 98 Elsevier Science Ltd. All rights reserved.