Recent improvements in the numerical scheme of estimating field-aligned current systems from ground magnetometer records

The capability of ground-based magnetometer data of estimating field-aligned current system is discussed. Starting with some basic equations governing electrodynamic parameters in the ionosphere, the author describes both the advantages and limitations of the algorithms known as magnetogram-inversion techniques. It is pointed out that the proposed numerical scheme has been considerably improved so that simultaneous measurements of electric fields, conductivities, and field-aligned currents by satellites and radars can be incorporated in a consistent manner. One of the advantages of the magnetogram-inversion technique is that, since the technique deduces the global distribution of various electrodynamic quantities in the ionosphere with a time resolution of several minutes, it is possible to compare their spatial distributions with each other, especially for the auroral region. Results on important characteristics of auroral electrojets are presented