Computing magnetospheric equilibria with anisotropic pressures

Wu, Li‐Tzy; Toffoletto, F.; Wolf, R. A.; Lemon, C.

doi:10.1029/2008ja013556

Cited by 6 publications

(6 citation statements)

References 43 publications

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“…Zaharia et al [] fed their 3‐D equilibrium code with anisotropic pressure in the equatorial plane from the UNH‐RAM ring current model [ Jordanova et al , ] and analyzed the computed magnetic fields and electric fields during a geomagnetic storm. Wu et al [] extended another equilibrium code RCM‐E, which has already coupled with the RCM, to include anisotropic pressure. They also proposed the possibility of coupling the equilibrium code with the CRCM.…”

Section: Introductionmentioning

confidence: 99%

Pressure anisotropy in global magnetospheric simulations: Coupling with ring current models

et al. 2013

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[1] We have recently extended the global magnetohydrodynamic (MHD) model BATS-R-US to account for pressure anisotropy. Since the inner magnetosphere dynamics cannot be fully described even by anisotropic MHD, we coupled our anisotropic MHD model with two inner magnetospheric models: the Rice Convection Model (RCM) and the Comprehensive Ring Current Model (CRCM). The coupled models provide better representations of the near-Earth plasma, especially during geomagnetic storms. In this paper, we present the two-way coupling algorithms with both ring current models. The major difference between these two couplings is that the RCM assumes isotropic and constant pressures along closed field lines, while the CRCM resolves pitch angle anisotropy. For model validation, we report global magnetosphere simulations performed by the coupled models. The simulation results are compared to the results given by the coupled isotropic MHD and ring current models. We find that in the global MHD simulations coupled with ring current models, pressure anisotropy results in a thinner magnetosheath, a shorter tail, a much smaller Earthward plasma jet from the tail reconnection site, and is also important in controlling the magnetic field configuration. The comparisons with satellite data for the magnetospheric event simulations show improvements on reproducing the measured tail magnetic field and inner magnetospheric flow velocity when including pressure anisotropy in the ring current model coupled global MHD model.

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Section: Introductionmentioning

confidence: 99%

Pressure anisotropy in global magnetospheric simulations: Coupling with ring current models

et al. 2013

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“…Zaharia et al [2004] computed 3-D force-balanced magnetospheric configurations with their 3-D equilibrium code and applied to magnetic storm simulations. Wu et al [2009] extended a friction code equilibrium solver to include pressure anisotropy. These studies provide very interesting insight of how anisotropic pressures modify the magnetic field and current configuration in the inner magnetosphere.…”

Section: Introductionmentioning

confidence: 99%

Pressure anisotropy in global magnetospheric simulations: A magnetohydrodynamics model

et al. 2012

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[1] In order to better describe the space plasmas where pressure anisotropy has prominent effects, we extend the BATS-R-US magnetohydrodynamics (MHD) model to include anisotropic pressure. We implement the anisotropic MHD equations under the double adiabatic approximation with an additional pressure relaxation term into BATS-R-US and perform global magnetospheric simulations. The results from idealized magnetospheric simulations confirm previous studies: pressure anisotropy widens the magnetosheath, increases the density depletion in the vicinity of the magnetopause, enhances the nightside plasma pressure, and introduces an eastward ring current. In addition, we find that the flow speed in the magnetotail is significantly reduced by including pressure anisotropy in MHD simulations. Our model is validated through comparing the simulations to the THEMIS data on both the dayside and nightside of the magnetosphere during quiet times. The comparison to the results from isotropic MHD simulations implies that although anisotropic MHD is comparable to isotropic MHD in matching the measurement, it improves the simulated plasma velocity in some cases.

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“…The coupled MHD‐RCM code showed significantly higher inner magnetospheric particle pressures and strong region 2 Birkeland currents, as well as partial shielding of the inner magnetosphere from the main force of the convection electric field [ De Zeeuw et al , 2004]. Preliminary results from RCM‐E that was modified to include the effect of anisotropic pressures were presented by Wu et al [2009]. Using one‐dimensional empirical fits to observed plasma pressure anisotropies [ Lui et al , 1994], it was found that the magnetic field may increase in the anisotropic case as much as 30% near the equatorial plane in the transition region between the inner magnetosphere and the magnetotail.…”

Section: Introductionmentioning

confidence: 99%

Comparative study of ring current development using empirical, dipolar, and self‐consistent magnetic field simulations

2010

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[1] The effects of nondipolar magnetic field configuration and the feedback of a self-consistently computed magnetic field on ring current dynamics are investigated during a double-dip storm with minima SYM-H = −90 nT at ∼2000 UT, 20 November, and SYM-H = −127 nT at ∼1000 UT, 21 November 2002. We use our kinetic ring current-atmosphere interactions model with self-consistent magnetic field (RAM-SCB) to study the redistribution of plasma in the inner magnetosphere after its fresh injection from the plasma sheet. The kinetic model is fully extended to nondipolar magnetic (B) field geometry and two-way coupled with an Euler-potential-based equilibrium model that calculates self-consistently the three-dimensional magnetic field in force balance with the anisotropic ring current distributions. The ring current source population is inferred from LANL geosynchronous satellite data; a superdense plasma sheet observed during the second storm main phase contributes significantly to ring current buildup. We find that the bounce-averaged velocities increase while the bounce-averaged geocoronal hydrogen densities decrease on the nightside when a nondipolar B field is used. A depression of the ring current fluxes and a confinement of the ring current close to Earth are thus observed on the nightside as geomagnetic activity increases. In contrast to the dipolar case, the proton anisotropy increases considerably in the postnoon sector, and the nondipolar simulations predict the excitation of intense EMIC waves at large L shells. The total ring current energy and |Dst| index calculated with the self-consistent B field are in best agreement with observations, being smaller compared to the dipolar calculations but larger than the empirical B field predictions.Citation: Jordanova, V. K., S. Zaharia, and D. T. Welling (2010), Comparative study of ring current development using empirical, dipolar, and self-consistent magnetic field simulations,

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Computing magnetospheric equilibria with anisotropic pressures

Cited by 6 publications

References 43 publications

Pressure anisotropy in global magnetospheric simulations: Coupling with ring current models

Pressure anisotropy in global magnetospheric simulations: Coupling with ring current models

Pressure anisotropy in global magnetospheric simulations: A magnetohydrodynamics model

Comparative study of ring current development using empirical, dipolar, and self‐consistent magnetic field simulations

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