Deformation method for electromagnetic magnetospheric fields: 2. Application to the Earth's magnetosphere

摘要

A new magnetospheric magnetic field model given globally in terms of the Euler potentials is constructed. It complements the preexisting model magnetic fields with a possibility of straightforward inclusion of electric fields, especially those arising from temporal variations of the model magnetic field. The model is based on the deformation method, and a short review of the method is given. The model is parameterized with geometrical input parameters, for example such as location of the subsolar point, colatitudes of the cusp and nightside poleward boundary of the auroral oval, and radius of the tail. These primary parameters can be used to vary the overall geometry of the model in response to geomagnetic conditions. In addition, several secondary parameters can be varied to fit the model to the geometric constraints set by the primary parameters. The model is constructed by applying five consecutive deformations to an initial magnetic field configuration of a dipole field. Such a model construction is convenient if local perturbations to the model are considered: Perturbations can be first introduced as deformations to the dipole field using its fairly simple analytic nature and then embedded in a realistic field configuration by applying the presented deformations to the perturbed dipole field. The resulting magnetic field model compares well to a preexisting empirical model, and in addition, the current systems of the model are realistic including the major magnetospheric current systems: the dayside magnetopause current, ring current, and the cross-tail current.