Penetrating Convection Electric Field, Plasma Injection and Plasmasphere Disturbances

Akasofu, S.‐I.

doi:10.1007/978-94-010-1164-8_9

Astrophysics and Space Science Library

1977

DOI: 10.1007/978-94-010-1164-8_9

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Penetrating Convection Electric Field, Plasma Injection and Plasmasphere Disturbances

S.‐I. Akasofu¹

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1987

2019

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Cited by 2 publications

References 260 publications

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Spatial Gradients in Geomagnetic Storm Time Currents Observed by Swarm Multispacecraft Mission

et al. 2019

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This paper presents a comprehensive study of geomagnetic storm time currents using magnetic field recorded by multispacecraft polar‐orbiting mission, Swarm. During geomagnetic storm period, the magnetic field variations obtained after removing the internal geomagnetic field and quiet time contributions can be considered as a proxy for storm time currents and are found to follow the temporal profile of Dst index very closely. These variations at the equatorial crossings recorded by multiple‐spacecraft are used to estimate the Dst values and are found to have a good match with the ground‐based Dst index. The average deviation between these two is around 4–13%. We have estimated the asymmetry by taking the difference between the magnetic field variations at two local time sectors separated by 12 hr. The estimated asymmetry shows a good match with the AsyH‐index, especially when satellite traverses in the dawn‐dusk sector. In general, the magnetic field variations are stronger in the night‐to‐dusk sector than day‐to‐dawn sector, which could be due to the larger pressure‐gradients near night‐to‐dusk caused by ion movements. The important advantage of Swarm mission is that it provides an opportunity to investigate the longitudinal gradients in the storm time magnetic fields. It is observed that in general, the gradients are stronger during the main phase of the storm, centered near the equator with a latitudinal width of ~20–30° in both the hemispheres, and are supportive to the scenario of particle‐injection from the magnetotail. The stronger gradients are observed at higher latitudes (~40°) during the episodes of substorms and might be associated with the ionospheric/field‐aligned currents.

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Spatial Gradients in Geomagnetic Storm Time Currents Observed by Swarm Multispacecraft Mission

et al. 2019

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Evolution of the ring current during two geomagnetic storms

Lui¹,

McEntire²,

Krimigis³

1987

J. Geophys. Res.

229

176

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The progressive developments in the radial profiles of the particle pressure, plasma beta, and electric currents of the storm time ring current are investigated with data from the medium energy particle analyzer on the AMPTE Charged Particle Explorer spacecraft. Measurements of ions from 25 keV to 1 MeV, which carry 70–85% of the energy density of the entire ring current population, are used in this work. Two geomagnetic storms in September of 1984 are selected and four traversals of the equatorial ring current region during the course of each storm are studied. It is shown that enhancements in the particle pressure occur initially in the outer region and reach the inner region in the late phase of the storm. Structures suggestive of multiple particle injections are seen in the pressure profile. The leading and trailing edges of the particle injection structures are associated, respectively, with the depressions and enhancements of the westward current densities of the ring current. Plasma beta occasionally increases to values of the order of 1 in some regions of the ring current from prestorm values of the order of 0.1 or less. It is also found that the location of the maximum ring current particle pressure can be several earth radii from where the most intense westward ring current flows. This is a consequence of the dominance of pressure gradient current over the current associated with the magnetic field line curvature and particle anisotropy.

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Penetrating Convection Electric Field, Plasma Injection and Plasmasphere Disturbances

Cited by 2 publications

References 260 publications

Spatial Gradients in Geomagnetic Storm Time Currents Observed by Swarm Multispacecraft Mission

Spatial Gradients in Geomagnetic Storm Time Currents Observed by Swarm Multispacecraft Mission

Evolution of the ring current during two geomagnetic storms

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