Simulation study on fundamental properties of the storm‐time ring current

Ebihara, Yusuke; Ejiri, Masaki

doi:10.1029/1999ja900493

Cited by 190 publications

(225 citation statements)

References 84 publications

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“…As a result of gradient-curvature-drift effects the extra-hot ions are prevented from convecting deep into the dipole where their pressure can be amplified (e.g. Ebihara and Ejiri, 2000;Liemohn et al, 2001;Kozyra and Liemohn, 2003). This likely contributes to the fact that high-speed-stream-driven storms (typically storms following coronal interaction regions in the solar wind), with extended periods of fast solar wind and an enhanced hot ion plasma sheet, tend to have poor D st signatures (e.g.…”

Section: Resultsmentioning

confidence: 99%

Solar wind dependence of ion parameters in the Earth's magnetospheric region calculated from CLUSTER observations

Denton

Taylor

2008

Ann. Geophys.

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Abstract. Moments calculated from the ion distributions (∼0-40 keV) measured by the Cluster Ion Spectrometry (CIS) instrument are combined with data from the Cluster Flux Gate Magnetometer (FGM) instrument and used to characterise the bulk properties of the plasma in the nearEarth magnetosphere over five years (2001)(2002)(2003)(2004)(2005). Results are presented in the form of 2-D xy, xz and yz GSM cuts through the magnetosphere using data obtained from the Cluster Science Data System (CSDS) and the Cluster Active Archive (CAA). Analysis reveals the distribution of ∼0-40 keV ions in the inner magnetosphere is highly ordered and highly responsive to changes in solar wind velocity. Specifically, elevations in temperature are found to occur across the entire nightside plasma sheet region during times of fast solar wind. We demonstrate that the nightside plasma sheet ion temperature at a downtail distance of ∼12 to 19 Earth radii increases by a factor of ∼2 during periods of fast solar wind (500-1000 km s −1 ) compared to periods of slow solar wind (100-400 km s −1 ). The spatial extent of these increases are shown in the xy, xz and yz GSM planes. The results from the study have implications for modelling studies and simulations of solar-wind/magnetosphere coupling, which ultimately rely on in situ observations of the plasma sheet properties for input/boundary conditions.

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Section: Resultsmentioning

confidence: 99%

Solar wind dependence of ion parameters in the Earth's magnetospheric region calculated from CLUSTER observations

Denton

Taylor

2008

Ann. Geophys.

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“…Many storms have been simulated based on the convection paradigm (Lee et al, 1983;Takahashi et al, 1990;Kozyra et al, 1998;Ebihara and Ejiri, 2000;Jordanova et al, 2001;Liemohn et al, 2001). In these calculations the magnetic field was in most cases a dipole, and the electric field was taken to be the Volland-Stern or other empirical convection electric field model.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

“…The influence of changing the initial conditions is shown in Fig. 5d, where we computed the plasma sheet number density from the solar wind number density as N ps =0.025 N sw +0.395 (Ebihara and Ejiri, 2000). The temperature was held constant at 5 keV.…”

Section: Particle Tracing In the Large-scale Time-varying Fieldsmentioning

confidence: 99%

Role of substorm-associated impulsive electric fields in the ring current development during storms

2005

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Abstract.Particles with different energies produce varying contributions to the total ring current energy density as the storm progresses. Ring current energy densities and total ring current energies were obtained using particle data from the Polar CAMMICE/MICS instrument during several storms observed during the years 1996-1998. Four different energy ranges for particles are considered: total (1-200 keV), low (1-20 keV), medium (20-80 keV) and high (80-200 keV). Evolution of contributions from particles with different energy ranges to the total energy density of the ring current during all storm phases is followed. To model this evolution we trace protons with arbitrary pitch angles numerically in the drift approximation. Tracing is performed in the large-scale and small-scale stationary and time-dependent magnetic and electric field models. Small-scale time-dependent electric field is given by a Gaussian electric field pulse with an azimuthal field component propagating inward with a velocity dependent on radial distance. We model particle inward motion and energization by a series of electric field pulses representing substorm activations during storm events. We demonstrate that such fluctuating fields in the form of localized electromagnetic pulses can effectively energize the plasma sheet particles to higher energies (>80 keV) and transport them inward to closed drift shells. The contribution from these high energy particles dominates the total ring current energy during storm recovery phase. We analyse the model contributions from particles with different energy ranges to the total energy density of the ring current during all storm phases. By comparing these results with observations we show that the formation of the ring current is a combination of large-scale convection and pulsed inward shift and consequent energization of the ring current particles.

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“…Ebihara and Ejiri (2000) conducted a parametric study of the influence of the near-Earth plasma sheet temperature on the ring current, determining that, for a given convection strength, there is an ideal temperature that will yield the maximum magnetic perturbation. For their computational setup, this temperature was around 5 keV.…”

Section: Ring Current Inputmentioning

confidence: 99%

Ring Current Energy Input and Decay

Kozyra

Liemohn

2003

Space Science Reviews

122

104

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Abstract.A new view of the ring current as an active element in the geospace system has emerged in which the ring current responds not only to changing convection electric fields imposed by solar wind interactions but to internal dynamics of the magnetosphere-ionosphere-atmosphere (geospace) system. Variations in the plasma sheet density, temperature and composition, saturation of the polar cap potential drop (and presumably the cross-tail potential drop), modifications to the imposed convection potential in the inner magnetosphere due to ring current shielding effects, the presence of a pre-existing ring current population, storm-substorm coupling, and strong convection with and without accompanying substorm activity all have an impact on the ring current strength, formation and loss. All of these internal processes imply that the geoeffectiveness of a solar wind driver cannot be predicted on the basis of the characteristics of the driver alone but must reflect key aspects of the dynamically changing geospace environment, itself. This review gives a summary of new information on ring current input and decay processes focusing on implications for the global geospace response to solar wind drivers during magnetic storms and on open questions that can be addressed with new ENA imaging techniques.

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Simulation study on fundamental properties of the storm‐time ring current

Cited by 190 publications

References 84 publications

Solar wind dependence of ion parameters in the Earth's magnetospheric region calculated from CLUSTER observations

Solar wind dependence of ion parameters in the Earth's magnetospheric region calculated from CLUSTER observations

Role of substorm-associated impulsive electric fields in the ring current development during storms

Ring Current Energy Input and Decay

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