Pioneers of Electric Currents in Geospace

Abstract:

Abstract

This presentation will give an overview of the development of our understanding of the electric currents in geospace. Traditionally it has been accepted that the German British scientist Alfred Lothar Schuster in 1908 was the first to introduce a conducting layer in the upper atmosphere in order to explain the tidal motions of the Earth’s magnetic field by electric currents on a global scale. Since then the technique to invert magnetic field data to patterns og global current systems have been greatly improved by the introduction of models of the height integrated conductivities.

The auroral zone ionosphere plays an important role in the electrodynamic coupling between geospace and the upper polar atmosphere. The Norwegian Physicist Kristian Birkeland introduced in 1908 a theory where he proposed that charged particle rays from the Sun, when approaching the Earth, are forced by the magnetic field to carry currents along the field lines toward the poles, and that these currents are closed in a horizontal current along the auroral arc. This theory was not well appreciated by his contemporary colleagues and was not fully accepted until the Space Age when satellite observations confirmed the presence of field aligned currents at high latitudes.

Based on incoherent scatter radar experiments during the last 35 years, it has been possible to show that by combining observed electric fields and winds together with the height integrated conductivities, the magnetic fluctuations simultaneously observed on ground are the result of the height integrated currents in the ionosphere.