Abstract
Abstract. Based on a data pool of 79 yearly files of space magnetometer data by Polar, Cluster, Geotail, and THEMIS satellites between 1995 and 2013, we developed a new quantitative model of the global shape of the magnetospheric equatorial current sheet as a function of the Earth's dipole tilt angle, solar wind ram pressure, and interplanetary magnetic field (IMF). This work upgrades and generalizes an earlier model of Tsyganenko and Fairfield (2004) by extending the modeling region to all local times, including the dayside sector. In particular, an essential feature of the new model is the bowl-shaped tilt-related deformation of the equatorial surface of minimum magnetic field, similar to that observed at Saturn, whose existence in the Earth's magnetosphere has been demonstrated in our recent work (Tsyganenko and Andreeva, 2014).
Highlights
The global geometry of the Earth’s distant magnetic field is determined by the position and shape of principal boundaries or sheets, where most of the magnetospheric electric currents are concentrated
The large-scale configuration and magnitude of those currents is controlled by the external factors such as the solar wind ram pressure and the interplanetary magnetic field (IMF)
The most recent and detailed study in that area was done by Tsyganenko and Fairfield (2004; referred to as TF04), who developed a detailed empirical model of the tiltand IMF-related asymmetries in the observed shape of the tail current sheet, using magnetometer data of Geotail and Polar spacecraft taken during 1994–2002 and 1998–2002, respectively
Summary
The global geometry of the Earth’s distant magnetic field is determined by the position and shape of principal boundaries or sheets, where most of the magnetospheric electric currents are concentrated. Because the electric currents in equilibrium configurations tend to concentrate in the regions with the weakest magnetic field, we concluded that the bowl-shaped deformation is a natural result of the combination of two basic types of magnetospheric asymmetries: the day–night asymmetry due to the solar wind compression and the north–south asymmetry due to the planetary dipole tilt Based on this conjecture and using a large set of data from the Polar, Cluster, Geotail, and THEMIS satellites, we found that the bowl-like deformation is clearly present in the terrestrial magnetosphere and reveals itself in the shape of a best-fit surface, approximating the location of the near-equatorial region where the radial component of the magnetic field changes polarity
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