Reply to comment by J.‐P. St.‐Maurice on “Nonlinear electron heating by resonant shear Alfvén waves in the ionosphere”

Lu, J. Y.; Rankin, R.; Marchand, R.; Tikhonchuk, V. T.

doi:10.1029/2005gl023149

Cited by 3 publications

(3 citation statements)

References 9 publications

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“…Finally, it should be mentioned that this work is limited to small current amplitude systems. For large currents (>10 μ A/m 2 ), the situation could be much more complicated: (1) associated density perturbation could significantly affect the behavior of the plasma; and (2) ionospheric electrons can be heated by shear Alfvén waves through Joule dissipation, which may produce significant ionization and further feedback on the wave amplitude and structure [ Lu et al , 2005a, 2005b].…”

Section: Discussionmentioning

confidence: 99%

Electromagnetic waves generated by ionospheric feedback instability

Wang

Rankin

et al. 2008

J. Geophys. Res.

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[1] A new interactive M-I coupling model that describes the dynamic interaction between magnetospheric dispersive waves, compressional modes, and auroral electron precipitations is applied to investigate the geomagnetic electromagnetic pulsations observed in Earth's magnetosphere in terms of magnetospheric waves triggered by ionospheric feedback instability. Two new aspects of this work are that (1) we treat the full nonlinear MHD equations, i.e., include the full compressional modes and their coupling with shear Alfvén waves in the magnetosphere; and (2) the height-integrated Pedersen conductivity is treated as a dynamic parameter by electrodynamically coupling the 2D finite element wave model ''TOPO'' to the ionospheric ionization model ''GLOW''. It is shown that the feedback instability can be triggered by a very small-scale, small amplitude density perturbation; and the small-scale electromagnetic oscillations and their associated density fluctuations observed in magnetosphere can be attributed to the feedback instability. We demonstrate that, unlike in a field line resonance where the ponderomotive force causes the plasma to move mainly along the field line, the plasma in the feedback instability is distributed either as a bump or a cavity along a field line and leads to a multibanded structure in the radial direction. The nonlinear feedback instability model can successfully explain the formation of plasma density and electromagnetic perturbations with the same frequency, which disagree with current FLR scenario.

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Section: Discussionmentioning

confidence: 99%

Electromagnetic waves generated by ionospheric feedback instability

Wang

Rankin

et al. 2008

J. Geophys. Res.

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“…It should be mentioned that this work is limited to small current amplitude systems. For large currents (>10 μ A/m 2 ), ionospheric electrons can be heated by resonant standing shear Alfvén waves through Joule dissipation, which may produce significant ionization and feedback on the FLR amplitude and structure [ Lu et al , 2005a, 2005b]. In future work, we plan to incorporate this effect into the interactive M‐I coupling model to investigate the feedback of ionospheric conductivity on the physics of M‐I coupling and diurnal, seasonal and solar cycle variations due to this feedback.…”

Section: Discussionmentioning

confidence: 99%

“…Precipitating electrons from the magnetosphere provide a direct source of ionization in the ionosphere [ Atkinson , 1970]. Heated electrons by Joule dissipation provide another possibility to produce additional ionizations for large amplitude current systems [ Lu et al , 2005a, 2005b]. When the ionospheric conductivity is allowed to vary in a background driving electric field, a so‐called feedback instability can be set up [ Atkinson , 1970; Sato , 1978].…”

Section: Introductionmentioning

confidence: 99%

Electrodynamics of magnetosphere‐ionosphere coupling and feedback on magnetospheric field line resonances

Rankin

Marchand

et al. 2007

J. Geophys. Res.

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[1] We present a new dynamic model that describes coupling between standing inertial or ion-acoustic-gyroradius-scale shear Alfvén waves, compressional modes, and auroral density disturbances. The model is applied to the excitation of field line resonances (FLRs) in dipolar and stretched geomagnetic fields in Earth's magnetosphere. Magnetosphereionosphere coupling is included by accounting for the closure of magnetospheric fieldaligned currents (FACs) through Pedersen currents in the ionosphere. A second new aspect is that the height-integrated Pedersen conductivity is treated as a dynamic parameter by electrodynamically coupling the two-dimensional finite element wave model ''Topo'' to the ionospheric ionization model ''Global Airglow Model (GLOW).'' We demonstrate that field line stretching brings the equatorial plasma b above unity, where the reduced MHD formulism for low-frequency plasma breaks down. As an application of our model, we study a specific FLR event observed on 31 January 1997, when the NASA FAST satellite was over the Canadian Auroral Network for the OPEN Program Unified Study (CANOPUS) Gillam station. Using geomagnetic fields computed from the T96 magnetic field model, we show that auroral electron precipitation produces strong Pedersen conductivity enhancements that control the final amplitude and width of the excited FLR, along with the amplitude of associated density fluctuations. The predictions of the model are generally consistent with observations of this event.

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Nonlinear dispersive scale Alfvén waves inmagnetosphere-ionosphere coupling: Physical processes and simulation results

Zhao

2012

Chin. Sci. Bull.

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Dispersive Alfvén waves (DAWs) have been demonstrated to play a significant role in auroral generation of the magnetosphereionosphere coupling system. Starting from a two fluid reduced MHD model, we summarize the frequency, temporal and spatial characteristics of magnetospheric DAWs. Then, the nonlinear kinetic and inertial scale Alfvén waves are studied, and we review some theoretical aspects and simulation results of dispersive Alfvén waves in Earth's magnetosphere. It is shown that dispersive standing Alfvén waves can generate the field-aligned currents which transport energy into the auroral ionosphere, where it is dissipated by Joule heating and energy lost due to electron precipitation. The Joule dissipation can heat the ionospheric electron and produce changes in the ionospheric Pedersen conductivity. As a feedback, the conducting ionosphere can also strongly affect the magnetospheric currents. The ponderomotive force can cause the plasma to move along the field line, and generate ionospheric density cavity. The nonlinear structuring can lead to a dispersive scale to accelerate auroral particle, and the Alfvén waves can be trapped within the density cavity. Finally, we show the nonlinear decay of dispersive Alfvén waves related to two anti-propagating electron fluxes observed in the auroral zone. dispersive Alfvén wave, magnetosphere ionosphere coupling, auroral zone

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Reply to comment by J.‐P. St.‐Maurice on “Nonlinear electron heating by resonant shear Alfvén waves in the ionosphere”

Cited by 3 publications

References 9 publications

Electromagnetic waves generated by ionospheric feedback instability

Electromagnetic waves generated by ionospheric feedback instability

Electrodynamics of magnetosphere‐ionosphere coupling and feedback on magnetospheric field line resonances

Nonlinear dispersive scale Alfvén waves inmagnetosphere-ionosphere coupling: Physical processes and simulation results

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