High-latitude particle traps and related phenomena

Antonova, A.E.

doi:10.1016/1350-4487(96)00016-9

Cited by 19 publications

(12 citation statements)

References 2 publications

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“…During this event, many test particles with large equatorial crossing points underwent so‐called Shabansky orbits [ Shabansky , 1971]. As warm ions drift into the dayside magnetosphere, those at high‐ L encounter regions where the plane of minimum field strength bifurcates, shifting from the equatorial region to high latitudes near the cusp [ Antonova , 1996]. This leads to the confinement of some particles to high latitudes on the dayside.…”

Section: Resultsmentioning

confidence: 99%

Physical mechanisms of compressional EMIC wave growth

et al. 2010

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electromagnetic ion cyclotron (EMIC) waves were observed on the ground by the Canadian Array for Realtime Investigations of Magnetic Activity (CARISMA) network of magnetometers between L = 4 and L = 6 in response to a significant magnetospheric compression. Here a new MHD/particle method for studying EMIC wave growth in the magnetosphere is used to provide a detailed study of the compression event. We compare equatorial field line crossings of NASA's Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft and CARISMA observation sites to frequency-integrated wave growth rates from the MHD/particle method. Simulated temperatures were constant in time, suggesting an absence of energizing processes during this event. Many particles experienced so-called Shabansky orbits during this event, in which their drift motion was confined to high latitudes in the dayside magnetosphere. We propose a new nonenergizing process, driven by ions undergoing Shabansky orbits, for generating ion temperature anisotropies. In addition, the fundamental role of the plasmasphere in generating EMIC waves from the free energy of warm ion temperature anisotropies is discussed.

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Section: Resultsmentioning

confidence: 99%

Physical mechanisms of compressional EMIC wave growth

et al. 2010

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“…Antonova and Shabansky (1968) and Shabansky (1968) noted that, with a minimum magnetic field existing off the equator in the outer cusp region (Figure 8), charged particles would not drift but rather branch off towards the magnetic field minimum at high latitudes. Shabansky (1971), Antonova and Shabansky (1975) and Antonova (1996) provided observational evidence for the trapping of energetic particles (of several tens of keV, up to a few hundreds of keV) in the high latitude region. Sheldon et al (1998) pointed out that an energetic electron will drift on a closed path around the front of the magnetosphere, and found that electrons could be trapped in the outer cusp.…”

Section: Energetic Electrons and Ions Trapped In The Cuspmentioning

confidence: 96%

Energetic Electrons as a Field Line Topology Tracer in the High Latitude Boundary/CUSP Region: Cluster Rapid Observations

et al. 2005

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Abstract. Energetic electrons (e.g., 50 keV) travel along field lines with a high speed of around 20 R E s )1 . These swift electrons trace out field lines in the magnetosphere in a rather short time, and therefore can provide nearly instantaneous information about the changes in the field configuration in regions of geospace. The energetic electrons in the high latitude boundary regions (including the cusp) have been examined in detail by using Cluster/RAPID data for four consecutive high latitude/cusp crossings between 16 March and 19 March 2001. Energetic electrons with high and stable fluxes were observed in the time interval when the IMF had a predominately positive B z component. These electrons appeared to be associated with a lower plasma density exhibiting no obvious tailward plasma flow (<20 keV). On the other hand, no electrons or only spike-like electron events have been observed in the cusp region during southward IMF. At that time, the plasma density was as high as that in the magnetosheath and was associated with a clear tailward flow. The fact that no stable energetic electron fluxes were observed during southward IMF indicates that the cusp has an open field line geometry. The observations indicate that both the South and North high latitude magnetospheric boundary regions (including both North and South cusp) can be energetic particle trapping regions. The energetic electron observations provide new ways to investigate the dynamic cusp processes. Finally, trajectory tracing of test particles has been performed using the Tsyganenko 96 model; this demonstrates that energetic particles (both ions and electrons) may be indeed trapped in the high latitude magnetosphere.

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“…Shabansky orbits have been studied previously in the context of trapped energetic particle dynamics [e.g., Antonova and Shabansky , 1968; Shao et al , 2005; Öztürk and Wolf , 2007] as well as cusp dynamics [e.g., Delcourt et al , 1992; Antonova , 1996; Sheldon et al , 1998; Delcourt and Sauvaud , 1998, 1999] but not in the context of warm plasma temperature anisotropy generation. Particles undergo Shabansky orbits in response to bifurcation of the B min ‐plane on the dayside of a compressed magnetosphere.…”

Section: Introductionmentioning

confidence: 99%

The role of Shabansky orbits in compression‐related electromagnetic ion cyclotron wave growth

2012

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[1] Electromagnetic ion cyclotron waves at high L values near local noon are often found to be related to magnetospheric compression events. These waves arise from temperature anisotropies in trapped warm plasma populations. There are several possible mechanisms that can generate these temperature anisotropies, including both energizing and nonenergizing processes. In this work we investigate a nonenergizing process arising from dayside bifurcated magnetic field minima. There are two kinds of behavior particles undergo in the presence of bifurcated minima: particles with high initial equatorial pitch angles (EPAs) are forced to execute so-called Shabansky orbits and mirror at high latitudes without passing through the equator, while those with lower initial EPAs will pass through the equator with higher EPAs than before; as a result, perpendicular energies near the equator increase at the cost of parallel energies. By using a 3-D particle tracing code in a tunable analytic compressed-dipole field, we explore the effects of Shabansky orbits on the anisotropy of the warm plasma and contrast with the anisotropy resulting from drift shell splitting. We show that Shabansky orbits are an independent source of temperature anisotropy for warm dayside ions.

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High-latitude particle traps and related phenomena

Cited by 19 publications

References 2 publications

Physical mechanisms of compressional EMIC wave growth

Physical mechanisms of compressional EMIC wave growth

Energetic Electrons as a Field Line Topology Tracer in the High Latitude Boundary/CUSP Region: Cluster Rapid Observations

The role of Shabansky orbits in compression‐related electromagnetic ion cyclotron wave growth

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