Interhemispheric Asymmetry Due To IMF By Within the Cusp Spherical Elementary Currents

Observations of interhemispheric asymmetry in the cusp region due to the interplanetary magnetic field (IMF) By component have been performed for years, but those observations typically are not simultaneous in both hemispheres and represent an average picture. Simultaneous instantaneous observations in both hemispheres are rare. We have combined four sets of magnetometers in Antarctica to produce equivalent ionospheric currents and current amplitudes at 10 s resolution using the spherical elementary current systems technique. These Antarctica spherical elementary currents are roughly conjugate to the northern hemisphere spherical elementary currents derived over Greenland and North America. We examined five intervals with large interplanetary magnetic field By positive and negative and demonstrate that the equivalent current pattern in opposite hemispheres are asymmetric with respect to one another during IMF By positive with the cusp throat opening towards the dusk in the northern hemisphere and towards the dawn in the southern hemisphere. This configuration reverses for interplanetary magnetic field By negative. In one of these events we examine the rotation of the equivalent currents in real time in the northern hemisphere. We also compare these results with virtual magnetometer predictions from the Space Weather Modeling Framework. Simultaneous spherical elementary currents observations in both hemispheres are important because they allow us to observe the evolution of the cusp throat during changing solar wind and interplanetary magnetic field conditions. Key Points We show the instantaneous equivalent ionospheric current orientation in the cusp for positive and negative IMF By We demonstrate that this pattern is reversed in opposite hemispheres Magnetically conjugate spherical elementary currents provide an opportunity to observe the high temporal variation in the cusp region