Impact of North-South Asymmetry of the Sun on the Solar Wind and Geomagnetic Activity

We study the possible impact of the north-south (N-S) asymmetry of the sun (known from excess of sunspot number - SSN - in one hemisphere over the other) on geomagnetic activity. It has been shown (Osherovich et al., 1984) that the quadrupole term in the solar global magnetic field B enhances B at one pole and decreases it at the other, thus changing the relative size of the two polar coronal holes and creating a N-S asymmetry in the solar wind outflow speed v. Can the N-S asymmetry of the sun modify the solar wind in the northern and southern hemispheres to the extent that this modulation produces a sizeable variation of geomagnetic indices reflecting the difference between the two hemispheres? We divide hourly data (NSSDC) of the space age into two data sets: northern and southern, depending on when the Earth is in each hemisphere, respectively. First, we study how the N-S asymmetry of SSN affects the solar wind quasi-invariant defined as the ratio of magnetic energy density to the ram pressure of the solar wind (Osherovich et al. 1999). Second, we explore how the N-S asymmetry of the solar wind (asymmetry of QI and its components) contributes to the N-S asymmetry of geomagnetic indices using new coupling functions (coupling between the solar wind and the magnetosphere). References: Osherovich, V., I. Tzur and E.B. Gliner, Theoretical model of solar corona during sunspot minimum I, Astrophys. J., 284, 412-428, 1984. Osherovich, V., J. Fainberg and R.G. Stone, Solar wind quasi-invariant as a new index of solar activity, Geophys. Res. Lett., 26(3), 401, 1999.