Global ena Image Simulations

Fok, M.‐C.; Moore, T. E.; Wilson, G.R.; Perez, J. D.; Zhang, X.X.; Brandt, P. C.; Mitchell, D. G.; Roelof, E. C.; Jahn, J.; Pollock, C. J.; Wolf, R. A.

doi:10.1023/b:spac.0000007514.56380.fd

Cited by 111 publications

(150 citation statements)

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“…Finally, a modification of the ionospheric conductivity could also lead to a new distribution of the current closure, thus affecting the resulting electric field (Fok et al, 2001). This can lead to twisted paths of particles (Fok et al, 2003), and thus to the appearance of split nose structures in that sector.…”

Section: Statisticsmentioning

confidence: 99%

“…It has to be noted that, since the electric field depends on the closure of the partial ring current through the ionosphere, a change in the ionospheric conductivity can modify the electric field pattern and thus drive to a twisted drift path of the particle in the ring current region (Fok et al, 2003). Considering that our simulations do not use a self consistent electric field model (i.e.…”

Section: Multi-nose Not Reproduced By the Modelmentioning

confidence: 99%

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Ion multi-nose structures observed by Cluster in the inner Magnetosphere

Vallat

Ganushkina

Dandouras³

et al. 2007

Ann. Geophys.

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Abstract. During the last 30 years, several magnetospheric missions have recorded the presence of narrow proton structures in the ring current region. These structures have been referred as "nose-like" structures, due to their appearance when represented in energy-time spectrograms, characterized by a flux value increase for a narrow energy range.Cluster's polar orbit, with a 4 R E perigee, samples the ring current region. The ion distribution functions obtained in-situ by the CIS experiment (for energies of ∼ 5 eV/q to 40 keV/q) reveal the simultaneous presence of several (up to 3) narrow nose-like structures. A statistical study (over one year and a half of CIS data) reveals that double nose structures are preferentially observed in the post-midnight sector. Also, the characteristic energy of the nose (the one observed at the lower energy range when several noses occur simultaneously) reveals a clear MLT dependence during quiet events (K p <2): a sharp transition in the energy range occurs in the pre-noon sector. Moreover, the multi-nose structures (up to 3 simultaneous noses) appear regardless of the magnetospheric activity level and/or the MLT sector crossed by the spacecraft.Numerical simulations of particles trajectories, using large-scale electric and magnetic field models are also presented. Most of the features have been accurately reproduced (namely the single and double noses), but the triple noses cannot be produced under these conditions and require to consider a more complex electric field model.

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Section: Statisticsmentioning

confidence: 99%

Section: Multi-nose Not Reproduced By the Modelmentioning

confidence: 99%

Ion multi-nose structures observed by Cluster in the inner Magnetosphere

Vallat

Ganushkina

Dandouras³

et al. 2007

Ann. Geophys.

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“…The most extensively used are the modifications of RAM (Ring current-Atmosphere interactions Model) developed initially by Fok et al (1993) and Jordanova et al (1996). There are now, at least, 5 variations of this model currently in use for the magnetospheric physics studies (e.g., Fok et al, 2003;Jordanova et al, 2006;Khazanov et al, 2004;Zheng et al, 2006;Liemohn et al, 2006), and every version has been developed in its own way during the last 20 years. These models solve the gyration and bounce averaged kinetic equation for the main hot particle species (H + , O + , He + , and electrons) in the keV energy range.…”

Section: Introductionmentioning

confidence: 99%

Storm-time ring current: model-dependent results

2012

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Abstract. The main point of the paper is to investigate how much the modeled ring current depends on the representations of magnetic and electric fields and boundary conditions used in simulations. Two storm events, one moderate (SymH minimum of −120 nT) on 6-7 November 1997 and one intense (SymH minimum of −230 nT) on 21-22 October 1999, are modeled. A rather simple ring current model is employed, namely, the Inner Magnetosphere Particle Transport and Acceleration model (IMPTAM), in order to make the results most evident. Four different magnetic field and two electric field representations and four boundary conditions are used. We find that different combinations of the magnetic and electric field configurations and boundary conditions result in very different modeled ring current, and, therefore, the physical conclusions based on simulation results can differ significantly. A time-dependent boundary outside of 6.6 R E gives a possibility to take into account the particles in the transition region (between dipole and stretched field lines) forming partial ring current and near-Earth tail current in that region. Calculating the model SymH* by Biot-Savart's law instead of the widely used Dessler-Parker-Sckopke (DPS) relation gives larger and more realistic values, since the currents are calculated in the regions with nondipolar magnetic field. Therefore, the boundary location and the method of SymH* calculation are of key importance for ring current data-model comparisons to be correctly interpreted.

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“…These newly injected plasmas tend to shield the inner magnetosphere from the external convection field through establishing field aligned currents that connect the ring current region and the subauroral ionosphere [Wolf, 1983;Fok et al, 2003;Ebihara and Fok, 2004]. Figure 6 plots the simulated potential drop at the ionosphere during the storm at the CRCM polar boundary and at 3 magnetic latitudes (mlat) equatorward to the boundary.…”

Section: Crcm Simulation Of the 20-21 November 2003 Stormmentioning

confidence: 99%

Modeling the superstorm in November 2003

et al. 2011

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[1] The superstorm on 20-21 November 2003 was the largest geomagnetic storm in solar cycle 23 as measured by Dst, which attained a minimum value of −422 nT. We have simulated this storm to understand how particles originating from the solar wind and ionosphere get access to the magnetosphere and how the subsequent transport and energization processes contribute to the buildup of the ring current. The global electromagnetic configuration and the solar wind H + distribution are specified by the Lyon-Fedder-Mobarry (LFM) magnetohydrodynamics model. The outflow of H + and O + ions from the ionosphere are also considered. Their trajectories in the magnetosphere are followed by a test-particle code. The particle distributions at the inner plasma sheet established by the LFM model and test-particle calculations are then used as boundary conditions for a ring current model. Our simulations reproduce the rapid decrease of Dst during the storm main phase and the fast initial phase of recovery. Shielding in the inner magnetosphere is established at early main phase. This shielding field lasts several hours and then breaks down at late main phase. At the peak of the storm, strong penetration of ions earthward to L shell of 1.5 is revealed in the simulation. It is surprising that O + is significant but not the dominant species in the ring current in our calculation for this major storm. It is very likely that substorm effects are not well represented in the models and O + energization is underestimated. Ring current simulation with O + energy density at the boundary set comparable to Geotail observations produces excellent agreement with the observed symH. As expected in superstorms, ring current O + is the dominant species over H + during the main to midrecovery phase of the storm.

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Global ena Image Simulations

Cited by 111 publications

References 0 publications

Ion multi-nose structures observed by Cluster in the inner Magnetosphere

Ion multi-nose structures observed by Cluster in the inner Magnetosphere

Storm-time ring current: model-dependent results

Modeling the superstorm in November 2003

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