A charge separation mechanism for the production of polar auroras and electrojets

Abstract

A mechanism for charge separation in the geomagnetically trapped radiation is described that may account for some observed phenomena associated with polar auroras and electrojet current systems. Surfaces of constant number density may be separated from surfaces of constant integral invariant within the trapped radiation as a result of distortion of the geomagnetic field by solar streams. Drift separation of protons and electrons will follow, and, for irregular distributions of plasma number density, electric fields will arise. A direct consequence of such polarization of the geomagnetically trapped radiation will be the polar-electrojet current systems. The polar auroras arise where energetic particles are discharged from regions of excess charge within the geomagnetically trapped radiation. A model for the discharge of such auroral particles is discussed. An interesting feature of the proposed mechanism is that the extreme thinness of auroral sheets appears to follow as the natural consequence of charge separation. This is shown analytically for a simple two-dimensional model of a trapped plasma.