Northern-Southern Hemispheric Asymmetry of Solar Wind Energy Input Into the Polar Ionosphere During a Prolonged Interval of Radial Interplanetary Magnetic Field

Abstract:

We present characteristics of magnetic variations near the magnetic poles and plasma convection patterns in the northern and southern polar regions observed during a prolonged interval of radial interplanetary magnetic field (IMF) on 5 March 2015. The OMNI IMF data indicate that the nearly earthward IMF conditions impinge on near-Earth space at 07:20-11:40 UT. The polar cap indices derived from magnetic field observations near the northern and southern magnetic poles (PCN and PCS indices, respectively) show significant difference between them (up to 1.5 mV/m with -0.4 mV/m for PCN and 1.1 mV/m for PCS) at ~08:00-10:00 UT, although they are comparable (with differences up to 0.5 mV/m) for several hours before and after this two-hour period. Moreover, the ionospheric potential and plasma convection patterns in the polar regions determined from Super Dual Auroral Radar Network (SuperDARN) radar observations reveal the existence of the multi-cell convection pattern in the northern hemisphere (with sunward flows over the ground station for PCN), while clear two-cell convection pattern exists in the southern hemisphere (with antisunward flows over the ground station for PCS). Based on these results, we discuss the mechanisms for the northern-southern hemispheric asymmetry of the energy transfer from the solar wind to the high-latitude ionosphere in terms of the magnetic configuration associated with magnetic reconnections under radial IMF conditions.