North-south asymmetry in the heliospheric current sheet and the IMF sector structure

Abstract

It is shown that in a heliomagnetic field the presence of a magnetic quadrupole in addition to a magnetic dipole introduces a north-south asymmetry in the heliospheric current sheet (HCS) about the heliographic equator. The dominant polarity of the interplanetary magnetic field (IMF) for the above type of current sheet reverses sign at a transition latitude θT, which lies in a heliohemisphere opposite to the one in which the HCS has more heliolatitudinal extension. The position of θT in the heliosphere and the north-south asymmetry introduced in the HCS change with the relative phase of the dipole and quadrupole components present in the solar magnetic field. The effect of the above type of asymmetric HCS in the IMF ‘mean sector width’ is evaluated and the results are in agreement with the observations during the minima of solar cycle 21.