Self-consistent ionospheric plasma density modifications by field-aligned currents: Steady state solutions

Details Self-consistent ionospheric plasma density modifications by field-aligned currents: Steady state solutions Self-consistent ionospheric plasma density modifications by field-aligned currents: Steady state solutions

Apr 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010jgra..11504216r&link_type=abstract

Journal of Geophysical Research, Volume 115, Issue A4, CiteID A04216

Physics

3

Ionosphere: Ionosphere/Magnetosphere Interactions (2736), Magnetospheric Physics: Magnetosphere/Ionosphere Interactions (2431), Magnetospheric Physics: Field-Aligned Currents And Current Systems (2409), Ionosphere: Auroral Ionosphere (2704), Ionosphere: Current Systems (2721)

Scientific paper

The magnetosphere and ionosphere are coupled by field-aligned currents that remove or deposit E-region electrons. Changes in electron number density modify ionospheric reflectivity, hence altering the magnetospheric current. Thus, self-consistent solutions are nontrivial. In this paper, we present 1-D steady states that self-consistently model modifications of ionospheric plasma density by field-aligned currents. These are used to investigate the width broadening and minimum plasma density of E-region plasma density cavities and the origin of small-scale features observed in downward current channels. A plasma density cavity forms and broadens if the maximum initial current density j$\parallel$0 exceeds jc = αne2he/(1 + 1/β), where α is the recombination coefficient, ne is the equilibrium E-region number density in the absence of currents, h is the E-region thickness, and β = $\SigmaP0/\Sigma_{A is the initial ratio of Pedersen to magnetospheric Alfvén conductivities. If a plasma density cavity forms, its final width increases monotonically with $\cal{W = 2B0/μ0VAαne2he, where B0 is the background magnetic field strength and VA is the magnetospheric Alfvén speed. The minimum E-region number density, and the finest length scale present in the steady state, both scale as 1/β. For typical ionospheric parameters and j$\parallel$0 = 5 μAm-2, the fine scale is comparable to or less than 6λe for β $\gtrsim$ 2, where λe is the electron inertial length. This suggests that electron inertial effects may become significant and introduce small-scale features, following the production of a single fine scale by depletion and broadening.

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