Effects of Non-radial Geomagnetic Field Lines on Evaluating Ionospheric Fields and Three-dimensional Current System from Ground Magnetic Data

Some improvements are made to the method developed by Kamide (KRM method) in evaluating ionospheric electric field, current and field-aligned currents from ground variations. Taking into account the effects of non-radial geomagnetic field lines on the ionospheric conductivity, a second-order partial differential equation for electric potential is rederived, which will come back to the original form of Kamide's equation when inclination equals to 90°.To show the effects of this improvement, an example is given and the results show a considerable effect of the non-radial field lines even in high latitude auroral regions. At magnetic latitude 67°, the correction by the improvement can be up to 21% for ionospheric current, and up to 10% (4kV) for electric potential. Finally, in this example, the rate of convergence in the iterative procedure increases, too, from 300 times to only 202 times.