Magnetosphere-ionosphere coupling through<i>E</i>region turbulence: 1. Energy budget

Dimant, Y. S.; Oppenheim, M. M.

doi:10.1029/2011ja016648

Cited by 15 publications

(42 citation statements)

References 71 publications

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“…Achieving improved quantitative agreement is therefore likely to require a nonlinear conductance representation representing the various sources of ionization and conductance [cf. Ridley et al ., ] and the effects of small‐scale turbulence and electron heating in the ionosphere responsible for anomalous conductivity [ Dimant and Oppenheim , , ]. Finally, we note that inductive and altitude‐dependent processes in the ionosphere that cannot be represented in terms of electrostatic solutions using height‐integrated conductivities may also need to be considered [cf.…”

Section: Discussionmentioning

confidence: 99%

Comparison of predictive estimates of high‐latitude electrodynamics with observations of global‐scale Birkeland currents

et al. 2017

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Two of the geomagnetic storms for the Space Weather Prediction Center Geospace Environment Modeling challenge occurred after data were first acquired by the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE). We compare Birkeland currents from AMPERE with predictions from four models for the 4–5 April 2010 and 5–6 August 2011 storms. The four models are the Weimer (2005b) field‐aligned current statistical model, the Lyon‐Fedder‐Mobarry magnetohydrodynamic (MHD) simulation, the Open Global Geospace Circulation Model MHD simulation, and the Space Weather Modeling Framework MHD simulation. The MHD simulations were run as described in Pulkkinen et al. (2013) and the results obtained from the Community Coordinated Modeling Center. The total radial Birkeland current, ITotal, and the distribution of radial current density, Jr, for all models are compared with AMPERE results. While the total currents are well correlated, the quantitative agreement varies considerably. The Jr distributions reveal discrepancies between the models and observations related to the latitude distribution, morphologies, and lack of nightside current systems in the models. The results motivate enhancing the simulations first by increasing the simulation resolution and then by examining the relative merits of implementing more sophisticated ionospheric conductance models, including ionospheric outflows or other omitted physical processes. Some aspects of the system, including substorm timing and location, may remain challenging to simulate, implying a continuing need for real‐time specification.

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Section: Discussionmentioning

confidence: 99%

Comparison of predictive estimates of high‐latitude electrodynamics with observations of global‐scale Birkeland currents

et al. 2017

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“…Various plasma instabilities produce FAI in the auroral E region. The most well‐known affecting the energetics of the auroral ionosphere [ Dimant and Oppenheim , , ] is the Farley‐Buneman instability [ Farley , ; Buneman , ]. The generated waves have been held responsible for electron heating [ Schlegel and St.‐Maurice , ; St.‐Maurice et al , ; Foster and Erickson , ; Bahcivan , ] with the electron temperatures rising from 300 K to as high as 4000 K as the background electric field increases.…”

Section: Introductionmentioning

confidence: 99%

Magnetic aspect sensitivity of high‐latitude E region irregularities measured by the RAX‐2 CubeSat

et al. 2014

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The second Radio Aurora Explorer (RAX‐2) satellite has completed more than 30 conjunction experiments with the Advanced Modular Incoherent Scatter Radar chain of incoherent scatter radars in Alaska and Resolute Bay, Canada. Coherent radar echoing occurred during four of the passes: three when E region electron drifts exceeded the ion acoustic speed threshold and one during HF heating of the ionosphere by the High Frequency Active Auroral Research Program heater. In this paper, we present the results for the first three passes associated with backscatter from natural irregularities. We analyze, in detail, the largest drift case because the plasma turbulence was the most intense and because the corresponding ground‐to‐space bistatic scattering geometry was the most favorable for magnetic aspect sensitivity analysis. A set of data analysis procedures including interference removal, autocorrelation analysis, and the application of a radar beam deconvolution algorithm mapped the distribution of E region backscatter with 3 km resolution in altitude and ∼0.1° in magnetic aspect angle. To our knowledge, these are the highest resolution altitude‐resolved magnetic aspect sensitivity measurements made at UHF frequencies in the auroral region. In this paper, we show that despite the large electron drift speed of ∼1500 m/s, the magnetic aspect sensitivity of submeter scale irregularities is much higher than previously reported. The root‐mean‐square of the aspect angle distribution varied monotonically between 0.5° and 0.1° for the altitude range 100–110 km. Findings from this single but compelling event suggest that submeter scale waves propagating at larger angles from the main E×B flow direction (secondary waves) have parallel electric fields that are too small to contribute to E region electron heating. It is possible that anomalous electron heating in the auroral electrojet can be explained by (a) the dynamics of those submeter scale waves propagating in the E×B direction (primary waves) or (b) the dynamics of longer wavelengths.

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“…Also, low‐frequency turbulence in the compressible ionospheric plasma can directly modify local ionospheric conductivities via a wave‐induced nonlinear current (NC) associated with plasma density irregularities [ Rogister and Jamin , 1975; Oppenheim , 1997; Buchert et al , 2006]. The physical nature of NC has been explained in the companion paper [ Dimant and Oppenheim , 2011]. While the RMS turbulent field 〈 δ 2 〉 1/2 is comparable to E 0 (the angular brackets denote spatial and temporal averaging), the NC is proportional to the density perturbations that, in saturated Farley‐Buneman (FB) turbulence, may reach tens percent at most.…”

Section: Introductionmentioning

confidence: 99%

Magnetosphere-ionosphere coupling throughEregion turbulence: 2. Anomalous conductivities and frictional heating

Dimant

Oppenheim

2011

J. Geophys. Res.

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[1] Global magnetospheric MHD codes using ionospheric conductances based on laminar models systematically overestimate the cross-polar cap potential during storm time by up to a factor of 2. At these times, strong DC electric fields penetrate to the E region and drive plasma instabilities that create turbulence. This plasma density turbulence induces nonlinear currents, while associated electrostatic field fluctuations result in strong anomalous electron heating. These two effects will increase the global ionospheric conductance. On the basis of the theory of nonlinear currents developed by Dimant and Oppenheim [2011], this paper derives the correction factors describing turbulent conductivities and calculates turbulent frictional heating rates. Estimates show that during strong geomagnetic storms the inclusion of anomalous conductivity can double the total Pedersen conductance. This may help explain the overestimation of the cross-polar cap potentials by existing MHD codes. The turbulent conductivities and frictional heating presented in this paper should be included in global magnetospheric codes developed for predictive modeling of space weather.Citation: Dimant, Y. S., and M. M. Oppenheim (2011), Magnetosphere-ionosphere coupling through E region turbulence: 2. Anomalous conductivities and frictional heating,

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Magnetosphere-ionosphere coupling throughEregion turbulence: 1. Energy budget

Cited by 15 publications

References 71 publications

Comparison of predictive estimates of high‐latitude electrodynamics with observations of global‐scale Birkeland currents

Comparison of predictive estimates of high‐latitude electrodynamics with observations of global‐scale Birkeland currents

Magnetic aspect sensitivity of high‐latitude E region irregularities measured by the RAX‐2 CubeSat

Magnetosphere-ionosphere coupling throughEregion turbulence: 2. Anomalous conductivities and frictional heating

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