Particle energization near an <i>X</i> line in the magnetotail based on global MHD fields

Joyce, G.; Chen, J.; Slinker, S. P.; Holland, D. L.; Harold, J. B.

doi:10.1029/95ja00963

Cited by 19 publications

(9 citation statements)

References 33 publications

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“…Doxas et al [1994] showed that abrupt density and temperature changes should occur near the neutral line. Joyce et al [1995] found that low-and high-energy ion populations coexist in the reconnection region, the relative importance of which depends upon elevation in the field reversal.…”

Section: Introductionmentioning

confidence: 99%

Structure of electron and ion distribution functions near a reconnection line

Smets¹,

Delcourt²,

Fontaine³

et al. 1996

J. Geophys. Res.

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We examine the transport of electrons and ions in the vicinity of an X line in the magnetotail, using single‐particle trajectory codes. It is shown that the particle distribution functions downstream of the reconnection region exhibit two distinct density domains separated by a narrow channel of enhanced densities. This narrow structure, which was first reported for ions by Martin and Speiser [1988] and referred to as a ridge, is due to particles which are essentially E × B convected from the lobes and experience large energy gains upon interaction with the neutral line. This structure weakly depends upon the characteristics of the inflowing population. As for the density domains on either side, they result from mixing of the particle populations during the reconnection process, high and low densities corresponding to particles originating earthward and tailward from the neutral line, respectively. The simulations also reveal fine low‐density structures embedded in the overall pattern. It is shown that these fine structures result from prominent gradient drift effects upon approach of the field reversal. It is demonstrated that, at a given observation point downstream of the reconnection region, the computed distribution functions strongly depend upon the azimuthal direction of view. An analytical estimate is proposed for the ridge location, which provides information on the neutral line characteristics.

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Section: Introductionmentioning

confidence: 99%

Structure of electron and ion distribution functions near a reconnection line

Smets¹,

Delcourt²,

Fontaine³

et al. 1996

J. Geophys. Res.

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“…The type of field models used generally fall into two separate classes: (1) macroscale models of the whole magnetosphere such as the Tsyganenko model [ Tsyganenko , 1989, 2002] or global MHD simulations or (2) simple models of mesoscale structures such as X‐lines and current sheets. For example, Joyce et al [1995] used self‐consistent electric field and magnetic field from a global MHD simulation to examine the effects of an X‐line on particle motion and found the distribution function contains two main components: a low‐energy component similar to the input distribution and a high‐energy population that has been accelerated near the midplane. Ashour‐Abdalla et al [1996, 1997] used test particle codes in conjunction with the Tsyganenko magnetic field model and found ion distribution functions in good qualitative agreement with those measured by the Geotail Comprehensive Plasma Instrument (CPI).…”

Section: Introductionmentioning

confidence: 99%

Effects of magnetospheric activity on the current sheet energy resonance ion distribution function signature

2008

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[1] In this paper, we discuss the effects of magnetospheric activity (as measured by Kp) on an ion distribution function signature of nonlinear particle dynamics in current sheet-like magnetic fields. The signature manifests itself as a series of peaks in the ion distribution function whose separation depends on the fourth root of the energy and parameters that describe the current sheet structure. We have found that the signature is evident in Geotail CPI data for Kp 3+ and that the larger the value of Kp, the closer the peaks are together. We have also used the energy resonance signature in conjunction with measurements of the magnetic field to determine a lower bound on the current sheet thickness and have found that this lower bound decreases for increasing levels of magnetospheric activity. For values of Kp > 4À, there are frequently peaks in the ion distribution function; however, their separations do not follow a simple rule.Citation: Holland, D. L., C. J. Bush, and W. R. Paterson (2008), Effects of magnetospheric activity on the current sheet energy resonance ion distribution function signature,

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“…The simulations produced phase-bunched, "cup-shaped" outgoing distributions. Two-dimensional test particle models have also been used to study particle dynamics in static, large-scale magnetospheric fields [Curran et al, 1987;Kaufmann et al, 1993; Ashour-Abdalla et al, , 1994Joyce et al, 1995]. Using a 2-D reduction of the Tsyganenko [1989] magnetic field model in conjunction with an imposed uniform cross tail electric field Er, Ashour-Abdalla et al [ 1991,1993] reported both large-and small-scale structures in the resulting distribution functions.…”

Section: Introductionmentioning

confidence: 99%

“…That is, the flux of energy and momentum-the Poynting vector-is determined by E x B and is self-consistent with the state of the global configuration. The computed properties of particle distributions are critically affected by the field models [Joyce et al, 1995]. To address the second issue, we consider simple analytic fields that allow us to more carefully analyze the sources and dependencies of these structures.…”

Section: Introductionmentioning

confidence: 99%

Resonance‐generated particle distributions in magnetotail x line configurations

Harold¹,

Chen²,

Joyce³

1998

J. Geophys. Res.

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Abstract. We present the results of a series of test particle simulations that model particle acceleration both in self-consistent magnetospheric fields obtained by magnetohydrodynamic (MHD) simulations and in simple x line fields. In particular, we investigate the physical mechanisms responsible for the formation of beam-like features ("beamlets") in the accelerated outgoing particle distributions reported by previous authors. We find that in our simulations these effects arise from the x line, where the field gradients are strong; despite this finding they can be readily explained by using a simple analysis based on the phase space partitioning and resonances in one-dimensional current sheets, consistent with the conclusions of previous authors. We confirm the expected scaling using both two-and one-dimensional models of the x line with imposed uniform electric field. However, we find that the formation of these features is critically dependent on both the field geometry and the electric field imposed at the x line. In particular, use of an MHD-generated nonuniform electric field model eliminates the energized particle population, while use of current sheets with a self-consistent width blurs the features until they are no longer easily discernible. This finding calls into question the degree to which the beamlet structures (those that depend on magnetic field gradients along the tail with a uniform electric field) can be observed in physical systems. It is believed that the magnetotail stores magnetic energy that can be released (via reconnection, current disruption, or other mechanisms) to cause large-scale disruptions in the geomagnetic environment. The magnetotail, in turn, is determined by and controls the particle populations that pass through it. Since these particle distributions can be measured directly by spacecraft, an understanding of the particle dynamics in the field-reversed region of the magnetotail can provide a means of relating local plasma measurements to the condition and history of the magnetosphere as a whole.The dynamics of particles moving through one-dimensional where f/is defined by

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Particle energization near an X line in the magnetotail based on global MHD fields

Cited by 19 publications

References 33 publications

Structure of electron and ion distribution functions near a reconnection line

Structure of electron and ion distribution functions near a reconnection line

Effects of magnetospheric activity on the current sheet energy resonance ion distribution function signature

Resonance‐generated particle distributions in magnetotail x line configurations

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