North-South Asymmetry of Sq Variations at Geomagnetically Conjugate Area

Asymmetry in the northern and southern hemispheres of Sq variations at the middle and low latitudes (within ±50°) is examined by analyzing observations from five pairs of geomagnetically conjugate stations of SuperMAG during quiet days. The results indicate that the asymmetries of the horizontal components of Sq variations (ASYM-X/Y) significantly vary with season and depend on latitude. First, ASYM-X of the three pairs of conjugate stations on the polar-side (44°) of and near (33° and 25°) the Sq focus are stronger from May through October than in the other seasons. ASYM-X of the two pairs of conjugate stations on the equatorial-side of focus (14° and 8°) is weak even in the June solstice. The intensity of ASYM-X on the polar-side is as strong as that of near focus from May through September and becomes as weak as that of the equatorial-side in other seasons. Second, the pattern of ASYM-Y on the polar-side is different from that at other latitudes, which basically consists of two parts. At other latitudes, ASYM-Y from April to October has a three-part pattern. The intensities of ASYM-Y in 06–10 LT and 14–18 LT decrease with increasing latitude from April to September. Finally, the north-south hemisphere asymmetry of the Sq variations is mainly caused by the asymmetry of the neutral winds. The seasonal and latitudinal variations of the asymmetry of the migrating tides, especially the zonal component, are essentially consistent with those of the Sq variations.