Interhemispheric magnetic conjugacy

Abstract

The concept of the inter-hemispheric magnetic conjugacy was investigated by comparing the conjugate points in the northern and southern hemispheres using the Tsyganenko T02 magnetic field model together with the International Geomagnetic Reference Field model for the internal magnetic field to follow the magnetic field lines. We studied the influence of the dipole tilt angle, solar wind (solar wind dynamic pressure and flow direction), and interplanetary magnetic field (IMF) parameters (IMF By and Bz) on the latitudinal and longitudinal differences between the foot points of magnetic field lines in both hemispheres. It was found that the dominant difference up to 30°is longitudinal, while latitudinal differences are about 2°. The largest differences are observed at dawn and dusk magnetic local times (MLTs) for large dipole tilt angles during high solar wind dynamic pressure (16-20 nPa) and large IMF By values (- 15 and 15 nT). The asymmetry of conjugate points is present due to nonzero values of IMF By, but there is no real dependence on the magnitude of IMF By. The influence of IMF Bz on the interhemispheric conjugacy depends on the sign of the IMF Bz but not much on the magnitude. The rotation of the tail current sheet from the Sun-Earth line by several degrees resulted in latitudinal differences of 1° and longitudinal differences of 15° at dawn and dusk MLTs for equinox. Testing the concept of magnetic conjugacy with previously reported auroral event observed at Tjörnes (Iceland) and Syowa (Antarctica) observatories confirmed the importance of taking into account the solar wind flow direction, especially when it deviates from radial by more than 2° Key Points magnetic conjugacy depends on dipole tilt angle and solar wind pressure magnetic conjugacy does not depend on IMF By value but depends on IMF Bz sign solar wind flow direction as shift of tail current sheet from Sun-Earth line ©2013. American Geophysical Union. All Rights Reserved.