Magnetosphere-Ionosphere Coupling Effects in the High Latitude Dayside Ionosphere

Abstract:

The high latitude dayside ionosphere both images and influences the characteristics and interactions of the overlying magnetosphere. In this region, magnetic field lines map to the high-altitude cusp and magnetic merging. Ionospheric densities, structure, and dynamics are shaped by the magnetosphere-ionosphere (M-I) coupling processes associated with particle precipitation and outflow, currents, and plasma flow. Distributed ground-based Global Positioning System (GPS) observations of total electron content (TEC) are used to characterize the high latitude dayside ionosphere. These TEC observations map directly to cold plasma structure in the magnetosphere, providing a geospace system perspective.

During disturbed conditions, M-I coupling processes at the plasmasphere boundary layer (PBL) and in the dayside magnetosphere drive a large-scale redistribution of cold ionospheric/plasmaspheric plasma through the geospace system. For cold plasmas of ionospheric origin, ExB redistribution entrains both low altitude ions (O⁺ in the ionospheric F region) and high altitude ions (plasmaspheric and topside H⁺ and He⁺) on the same geomagnetic flux tube. In this way, sunward plasma fluxes in an active plume occur at all altitudes from the ionosphere to the apex of the field lines in the convection-defined drift shell. These plasmas convect together to the ionospheric cusp at low altitudes and at high altitude from the outer plasmasphere in the dusk sector to the magnetopause on the dayside (see Figure). There the cold dense plasmaspheric plume can substantially impact the energy coupling in the dayside reconnection region. At lower altitudes, the effects of dayside merging carry this large-scale plasma redistribution poleward away from the cusp into the polar cap where an enhanced TEC tongue of ionization results, extending anti-sunward across polar latitudes to the midnight sector auroral oval. Individual polar cap patches are seen to be segmented from the tongue of ionization reflecting the effect of pulsed dayside magnetopause reconnection.

We combine ground and space-based observations to provide an overview of M-I coupling effects in the dayside high latitude ionosphere.