Contribution of Birkeland Currents to the Earth’s distant magnetic field

Abstract

Birkeland Currents are sheet-like electric currents flowing into the auroral zone and out of it; their circuit appears to be". closed far from Earth either by near-equatorial currents on the night side or by currents in or beyond the boundary with the solar wind. Because of the intricate configuration of those currents, their contribution to the distant magnetic field is unknown. Yet it is of great interest, for modeling the global magnetic field and for understanding effects claimed for such currents, on the position of the noon magnetopause ("erosion") and on that of the polar cusps. An initial effort to derive such a field will be described, assuming relatively weak currents on the background of a dipole field. The method uses Euler potentials (tt,P) (Stern, 1970), which satisfy B= Vtt x Vp, and it assumes the currents flow in thin sheets. Results of applying the Biot-Savart formula to this configuration will be described.