Hemispherical and latitudinal differences in the response of geomagnetic activity to recurrent solar wind streams

Abstract

The data-adaptive technique of Singular Spectrum Analysis isolates significant signal components from background noise in a time series. This methodology is adopted for analysis of indices of geomagnetic activity, interplanetary magnetic field (IMF) and solar wind parameters during an interval in 1974 marked by strong recurrent solar wind streams to bring out the latitudinal dependence and differences in the geomagnetic response between the northern and the southern hemispheres. The geoeffectiveness of the azimuthal component of IMF in the observed 28-day periodicity at low latitudes can be attributed to the seasonally dependent IMF polarity influence through the Russell–McPherron mechanism. In respect of the 14-day oscillation, the solar wind velocity, the variability and density which characterize the recurrent streams appear significant in their efficacy at subauroral and auroral latitudes as also in generating North–South asymmetry in the geomagnetic response. A clear difference in the response to recurrent solar wind streams, between the two hemispheres, is brought out with the southern (northern) hemisphere showing greater activity with ∼14-d (∼28-d) periodicity. The observed responses can be interpreted in terms of the geomagnetic changes associated with the sector structure and sector boundary of IMF through the Russell–McPherron (R–M) effect.