Energy sources of field‐aligned currents: Auroral electron energization

Wright, Andrew N.

doi:10.1029/2004ja010609

Cited by 3 publications

(2 citation statements)

References 23 publications

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“…The currents close through the ionosphere via Pedersen currents, as ions move horizontally to preserve quasi‐neutrality. Typical current densities are readily sustained in the upward current channel, since the magnetosphere provides a large reservoir of electrons [ Wright et al , 2002; Wright , 2005]. In contrast, downward currents can rapidly suppress the ionospheric number density (on a time scale of ∼30 s) and can lead to the formation of a plasma density cavity in the E‐region [ Doe et al , 1995; Blixt and Brekke , 1996; Karlsson and Marklund , 1999; Marklund et al , 2001; Aikio et al , 2002, 2004].…”

Section: Introductionmentioning

confidence: 99%

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

2010

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[1] 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 k0 exceeds j c = an e 2 he/(1 + 1/b), where a is the recombination coefficient, n e is the equilibrium E-region number density in the absence of currents, h is the E-region thickness, and b = AE P0 =AE A is the initial ratio of Pedersen to magnetospheric Alfvén conductivities. If a plasma density cavity forms, its final width increases monotonically with W = 2B 0 /m 0 V A an e 2 he, where B 0 is the background magnetic field strength and V A 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/b. For typical ionospheric parameters and j k0 = 5 mAm −2 , the fine scale is comparable to or less than 6l e for b^2, where l e 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.Citation: Russell, A. J. B., A. N. Wright, and A. W. Hood (2010), Self-consistent ionospheric plasma density modifications by field-aligned currents: Steady state solutions,

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Section: Introductionmentioning

confidence: 99%

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

2010

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“…The occurrence of such potentials are known to exist in the auroral region even though Alfvén waves have been observed as probable accelerators of electrons as well (cf. Ergun et al, 1998;Wright, 2005;Wygant et al, 2000).…”

Section: Observationsmentioning

confidence: 99%

Polar and Cluster observations of a dayside inverted-V during conjunction

et al. 2007

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Abstract.We investigate particle and fields data during a conjunction of the Polar and Cluster spacecraft. This conjunction occurs near the dayside cusp boundary layer when a dayside inverted-V was observed in the particle data of both satellites. Electron, ion, electric field, and magnetic field data from each satellite confirm that the dayside inverted-V (DSIV) structure is present at the location of both satellites and the electric fields persist from the altitude of the Polar (lower) spacecraft to the altitude of the Cluster spacecraft. We observe accelerated, precipitating electrons and upward ions along the magnetic field. In addition, large amplitude electric fields perpendicular to the ambient magnetic field seen by Polar and by Cluster suggest significant parallel electric fields associated with these events. For similar DSIV events observed by the Polar spacecraft, plasma waves (identified as possible Alfvén waves) have been observed to propagate in both directions along the magnetic field line. Future conjunctions will be necessary to confirm that DSIVs are associated with reconnection sites.

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Global MHD eigenmodes of the outer magnetosphere

Wright

Mann

2006

Magnetospheric ULF Waves: Synthesis and New Directions

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The global scale time-dependent behavior of the magnetosphere is naturally described in terms of MHD waves. As these waves propagate they transport energy throughout the system, couple different regions together and form part of the magnetospheric current circuit. Theory and observations of ULF waves have a tradition of developing together and provide much insight and understanding of the magnetosphere. A historical review is given by Hughes [1994]. The origins of theory date back to Dungey's [1954; 1967] consideration of MHD waves in a cold axisymmetric magnetic field. In this case only the fast and Alfvén modes exist, and were shown to decouple when the

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Energy sources of field‐aligned currents: Auroral electron energization

Cited by 3 publications

References 23 publications

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

Polar and Cluster observations of a dayside inverted-V during conjunction

Global MHD eigenmodes of the outer magnetosphere

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