On high-latitude convection field inhomogeneities, parallel electric fields and inverted-V precipitation events

Abstract

Assuming a certain horizontal distribution of the convection field at a certain altitude above the ionosphere, the associated electric field and current distributions in a vertical plane are calculated using a model with finite current-dependent conductivity along the magnetic field lines. It is seen that given the kind of horizontal distribution of E ‖ commonly observed by polar-orbiting satellites at inverted-V electron precipitation events, the calculated distribution of E ∥ is able to reproduce the basic spatial structure of the precipitation. It is also seen that the combined effect of a locally increased ionization within auroral forms and a large potential difference (Δ V) ∥ along the magnetic field lines at higher altitudes is a strong reduction of E ‖ within the auroral forms. From the basic features of the electric field, it is concluded that an interpretation of auroral precipitation in terms of a static E ∥ may require a mechanism that can support a large (Δ V) ∥ even at relatively weak current densities and at the same time allow local enhancements of the parallel conductivity within the region of non-zero E ∥. It is suggested that the magnetic mirroring combined with gyro-resonant wave-particle interactions may be a suitable mechanism.