"Interplanetary Magnetic Field and the Auroral Zones:"

J. W. Dungey, Phys. Rev. Let., 6, 47-49, 1961

This is a brief summary of "Interplanetary Magnetic Field and the Auroral Zones" by J. W. Dungey. This paper was one of the references in C. T. Russell's "The Structure of the Magnetopause," which I am attempting to summarize.

Summary

This is one of the earliest papers discussing the role of reconnection in creating and defining magnetospheric structure and behavior. This paper was inspired by Pioneer V's discovery that the IMF is fairly steady in behavior, allowing several predictions to be made based on IMF direction. Dungey concerns himself primarily with southward IMF, which results in reconnection in the equatorial plane.

When a steady flow around the earth is assumed (Dungey admits that this may not be a reliable approximation), the electric field found from the cross product of the flow vector and the earth's magnetic field exhibits equipotentials which coincide with observed current lines. The primary auroral acceleration, in this case, would take place at the neutral points, the current lines being the auroral field lines. Dungey predicts proton auroras before midnight and electron auroras after midnight, in accordance with the model's electric field directions.

In reading papers written way before my birth, I find it difficult to place the discussion in the proper context. Dungey states that if the IMF was northward, the topology of the magnetosphere-solar wind system would not allow open field lines, and hence the IMF points southward. So when did the physical community become aware that the IMF fluctuates in direction? I found it interesting and exciting that a single paper could contain such a large volume of relevant and vital information, even though he failed to notice the potential for reconnection during northward IMF. Indeed, the theory for northward IMF reconnection was probably worked out 6-12 months after the discovery of a steady northward IMF.

Return to "The Structure of the Magnetosphere" by C. T. Russell.