An empirical model of the substorm current wedge

Tsyganenko, N. A.

doi:10.1029/97ja01904

Cited by 20 publications

(19 citation statements)

References 19 publications

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“…In the subsequent expansion phase, the field collapses to a more dipole‐like configuration, which may be associated with the development of a substorm current wedge as suggested by McPherron et al [1973]. Tsyganenko [1997] developed an empirical model to describe the magnetic field produced by the current wedge.…”

Section: Introductionmentioning

confidence: 99%

Rice Convection Model simulation of the 18 April 2002 sawtooth event and evidence for interchange instability

et al. 2008

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[1] We present the results of a Rice Convection Model (RCM) simulation of the 18 April 2002 sawtooth event. This event occurred as a series of quasi-periodic substorms during fairly stable solar wind conditions. It is modeled by (1) prescribing a solar-wind-driven magnetic field model (T01_s) augmented by additional current loops representing the magnetic effects of the substorm current wedge and (2) by carefully specifying a substorm-phase-dependent plasma distribution at the RCM outer boundary at 8 R e such that a hot and attenuated plasma distribution is used after every substorm onset. The set of input parameters was adjusted to make the simulation results agree with the primary signatures of the sawtooth event, specifically the sequence of magnetic field stretching and dipolarization observed by the GOES spacecraft and the associated sharp increases and gradual decreases in the flux of energetic protons measured by the LANL/Synchronous Orbit Plasma Analyzer (SOPA) instruments on other geosynchronous spacecrafts. The results suggest the important role that higher temperature and lower density plasma-sheet plasma plays in producing flux enhancements at geosynchronous orbit. The results also confirm that induction electric fields associated with magnetic field collapse after substorm onsets can serve as a likely mechanism for the energization of particles up to 25 keV. Synthetic high-energy neutral atom images are compared with IMAGE/HENA measurements for 10-60 keV hydrogen atoms. Magnetic field dipolarization over a large range of local time resulted in a dramatic reduction in the plasma entropy parameter PV 5/3 on the boundary. The simulation indicates that the ring current intensified 10-20 minutes after every onset, associated with the injection of low PV 5/3 flux tubes through the boundary. The low PV 5/3 plasma also produced an interchange convection in the inner magnetosphere, which drives Birkeland currents in a quasi-periodic upward-downward pattern with a lifetime of 40-60 minutes and spatial extent of 1.5-2.0 hours. The results suggest that the spatial quasi-periodic and nearly north-south-aligned auroral arcs observed by an IMAGE/FUV WIC detector might be caused by interchange instability.

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Section: Introductionmentioning

confidence: 99%

Rice Convection Model simulation of the 18 April 2002 sawtooth event and evidence for interchange instability

et al. 2008

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“…Using the vector potential makes it possible to conserve ∇ · B = 0 and regularize the integrand in Eq. (24) by introducing a finite transverse scale length D = D(s), so that the denominator takes the form (Tsyganenko, 1997(Tsyganenko, , 2000. To keep the currents field-aligned, it suffices to set D(s) ∼ B −1/2 0 , so that the magnetic flux inside the electric current flow tube remains constant.…”

Section: Modelling the Magnetic Field Associated With Large-scale Birmentioning

confidence: 99%

“…In terms of a vector potential, the problem to calculating (Tsyganenko, 1997(Tsyganenko, , 2000. approach was developed independently by Ontiveros et al (2006) in their model of the R2 FACs and the magnetopause currents.…”

Section: Geodipole Tilt Effectsmentioning

confidence: 99%

Data-based modelling of the Earth's dynamic magnetosphere: a review

Tsyganenko

2013

Ann. Geophys.

119

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Abstract. This paper reviews the main advances in the area of data-based modelling of the Earth's distant magnetic field achieved during the last two decades. The essence and the principal goal of the approach is to extract maximum information from available data, using physically realistic and flexible mathematical structures, parameterized by the most relevant and routinely accessible observables. Accordingly, the paper concentrates on three aspects of the modelling: (i) mathematical methods to develop a computational "skeleton" of a model, (ii) spacecraft databases, and (iii) parameterization of the magnetospheric models by the solar wind drivers and/or ground-based indices. The review is followed by a discussion of the main issues concerning further progress in the area, in particular, methods to assess the models' performance and the accuracy of the field line mapping. The material presented in the paper is organized along the lines of the author Julius-Bartels' Medal Lecture during the General Assembly 2013 of the European Geosciences Union.

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“…(The simple type of Grad-Shafranov solution described in Appendix B, which assumed a locally constant plasma sheet thickness, is less applicable to a dipolarized region.) The magnetic field of the SCW is calculated following a method originally presented by Tsyganenko [1997]. This scheme is based on simple, flexible analytic expressions that represent the magnetic field due to a combination of two fuzzy wires that are circular (before stretching) to represent rapid near-Earth field dipolarization during substorm expansion phase.…”

Section: Magnetic Field Model For the Expansion Phasementioning

confidence: 99%

Rice Convection Model simulation of the substorm‐associated injection of an observed bubble into the inner magnetosphere: 1. Magnetic field and other inputs

et al. 2009

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[1] The objective of this work is a realistic Rice Convection Model (RCM) simulation of a modest substorm that occurred on 22 July 1998 and was observed by the Geotail spacecraft in the inner plasma sheet. It represents the first time the RCM has been used for detailed modeling of an inner magnetospheric event using data from a spacecraft in the inner plasma sheet beyond geosynchronous orbit to drive the model's time-dependent boundary conditions. Since this represents a substantial departure from past practice, we present, in this paper, a detailed account of how model inputs are determined. An accompanying paper presents results and interpretations. Model inputs are adjusted to achieve approximate consistency between RCM-computed values and measurements by Geotail, which was within the RCM modeling region near X GSM = À9 R E , Y GSM = 0. To represent the magnetic field in the growth phase, we utilize a Tsyganenko (1989) statistical magnetic field model, adjusted to agree with Geotail-measured pressure and magnetic field in a new way using analytic solutions to the linear Grad-Shafranov equation. The magnetic field during the expansion phase is represented by adding a substorm current wedge using formulas developed by Tsyganenko. Induction electric fields play a central role in these simulations, because they are large in the vicinity of the substorm injection region. We provide a detailed description of how induction electric fields are included in the RCM as well as a prescription of the electromagnetic gauge condition used in the code.

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An empirical model of the substorm current wedge

Cited by 20 publications

References 19 publications

Rice Convection Model simulation of the 18 April 2002 sawtooth event and evidence for interchange instability

Rice Convection Model simulation of the 18 April 2002 sawtooth event and evidence for interchange instability

Data-based modelling of the Earth's dynamic magnetosphere: a review

Rice Convection Model simulation of the substorm‐associated injection of an observed bubble into the inner magnetosphere: 1. Magnetic field and other inputs

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