Abstract
In recent years, quantitative analysis of the magnetosphere-ionosphere coupling and electrodynamics of the polar ionosphere received much attention. Though remarkable progress has been made in this field by using a variety of magnetogram inversion techniques in order to infer the global ionospheric current distribution, there is still a need for modeling ionospheric currents locally, over a certain region, for comparison with other geophysical ground-based and satellite observations. This paper presents a simple method for estimating equivalent ionospheric currents using magnetic field observations along a meridian chain of ground-based vector magnetometers. The method can be applied in an automatic fashion to any available magnetometer chain data, for example, from the DMI Greenland west coast chain. We first describe how we separate contributions to the observed geomagnetic variations from external (ionospheric) and internal (induced) sources. We then model the ionospheric electrojet by a sequence of narrow current strips and apply the Biot-Savart law to formulate an inversion problem. Using a regularization technique, we find a stable distribution of the equivalent ionospheric currents crossing the magnetometer chain in eastward and westward direction. Simulation tests and a case study (20 March 1999) are discussed in order to illustrate properties of the solution to the inverse problem and to present a practical tool, which is accessible through the DMI World Wide Web site.
