Origin and dynamics of thin auroral arcs
Abstract
Thin auroral structures are discussed from the side of observations, basic auroral arc theory and the non-linear response of the topside ionosphere. The reported structures of widths down to ~ 100 m are likely to be embedded in broader luminous regions. Determination of their width depends sensitively on the imaging contrast. The basic theory of auroral arcs, which attributes the energy carried by the primary electrons to the conversion of electromagnetic energy via field-aligned potential drops above the topside ionosphere, is incapable of reconciling the observed energies and current densities with narrow widths. The lowest values it allows for lie near 5 km. It is suggested that cool plasma, eroded at the boundaries of propagating auroral acceleration regions, creates upwelling ion tongues of narrow widths which are the sites of additional potentials drops, energy conversion and shear flows. They may well underlie the formation of thin auroral substructures.
- Publication:
-
Advances in Space Research
- Pub Date:
- January 1999
- DOI:
- 10.1016/S0273-1177(99)00374-9
- Bibcode:
- 1999AdSpR..23.1637H