Observation of a structured auroral field-aligned current system

Casserly, R. T.

doi:10.1029/ja082i001p00155

Cited by 13 publications

(2 citation statements)

References 23 publications

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“…Subsequently, the magnetic effects of the gross field-aligned current configuration associated with the auroral oval were reported by Zmuda et al [1967], and their spatial structure and diurnal behavior were described by Zmuda et al [1970], Armstrong and Zmuda [1970], Armstrong [1974], Zmuda and Armstrong [1974a, b], Berko et al [1975], and Sugiura [1975]. At the same time it was realized that field-aligned currents flowed in the region of discrete auroral arcs, and detailed studies of these current systems were carried out by using rocket-borne detectors [e.g., Cloutier et al, 1970Cloutier et al, , 1973Choy et al, 1971;Park and Cloutier, 1971;Vondrak et al, 1971;Whalen and McDiarmid, 1972;Arnoldy and Choy, 1973;Bryant et al, 1973;Maehlum and Moestue, 1974;Bosqued et al, 1974: Anderson andCloutier, 1975;Et•ans et al, 1917;Carlson and Kelley, 1977;Casserly, 1977] and by using satellite detectors [e.g., Hoffman and Evans, 1968;Hultqt•ist et al, 1971;Aubry et al, 1972; In the past, unambiguous conclusions based on correlative studies involving satellite and ground-based data have been difficult to achieve. This stems from the fact that ground-based instrumentation evaluates parameters which are averaged over scale sizes of hundreds to thousands of kilometers, while satellite instrumentation often provides in situ measurements pertaining to conditions in the immediate vicinity of the spacecraft.…”

Section: Introductionmentioning

confidence: 99%

The spatial relationship of field-aligned currents and auroral electrojets to the distribution of nightside auroras

Kamide¹,

Rostoker

1977

J. Geophys. Res.

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In this paper, nearly simultaneous sets of ground-based magnetometer data, magnetic perturbations recorded at 800-km altitude by the polar-orbiting Triad satellite and auroral imagery and information on precipitating electr6ns in the energy range 200 eV < E < 20 keV obtained from the DMSP satellites are analyzed for intervals of moderate magnetospheric activity during which substorms were in progress. It is found that the boundaries of intense (>2 kR at 5577,4,) auroral features coincide with the boundaries of field-aligned current regions defined by the Triad data. In the morning sector the downward field-aligned current flows in the poleward portion of the auroral oval, and the intensity of this current appears not to be a function of the intensity of the related auroral features. These results suggest that the current is carried by upgoing thermal electrons from the ionosphere. On the equatorward side of the oval the region of the upward field-aligned current coincides with the bright aurora regime and is probably carried by precipitating energetic electrons. In the evening sector, regions of intense upward field-aligned currents are found to coincide with discrete auroral arcs and fluxes of precipitating electrons with energies peaked at several keV in the region immediately poleward of the eastward electrojet. This region is thought to coincide with the extension of the westward electrojet from the morning sector, and precipitating electrons in the bright auroral forms are thought to carry the upward field-aligned current in this region. In a narrow latitudinal area poleward of the upward current where no auroral luminosity is detected, downward field-aligned current is often observed, indicating the importance of ionospheric thermal electrons carrying the downward current. This current is thought to be connected to the equatorward Pedersen current of the equatorward electric field that is dominant in the westward electrojet region. In the equatorward half of the evening auroral oval the diffuse aurora is located in the region of the downward field-aligned current and, in general, collocated with the eastward electrojet. Paschmannet al., 1972; Berko, 1973; Fairfield, 1973]. The possible connection between the auroral electrojets and the field-aligned currents has also been discussed theoretically ]. Further detailed studies of the gross Birkeland current configuration have yielded important information on the character of the currents and their relationship to both auroral luminosity and auroral electrojet flow. Yasuhara et al. [1975], Sugiura and Potemra [1976], lijima and Potemra [1976], and Kamide and Akasofu [1976a] have reported that the current flow is often unbalanced in the morning and evening sectors, excess current flowing into the auroral oval in the morning sector and out of the oval in the evening ;ector. Kamide et al. [1976a] have shown that in the morning ;ector the field-aligned current region coincides with the region of the westward electrojet, while Armstrong et al. [1975] have presented e...

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Section: Introductionmentioning

confidence: 99%

The spatial relationship of field-aligned currents and auroral electrojets to the distribution of nightside auroras

Kamide¹,

Rostoker

1977

J. Geophys. Res.

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“…particle detectors (0.5<E<20keY) was only 17% of that inferred from the on boardd magnetometer data, suggesting that low energy electrons might play an important role as current carriers. In a subsequent paper, CASSERLY (1977) showed that the rocket magnetometer observations were best described by a double sheet current system with a poleward step to the east of the rocket ground track. SESIANO and CLOUTIER (1976) have studied magnetometer data from a rocket launched into a multiple arc system, and found evidence for three pairs of antiparallel current sheets associated with the dis- proposed by VoNDRAK (1975).…”

Section: Currents Into Ionospherementioning

confidence: 99%

Electric and magnetic fields in the ionosphere and magnetosphere.

Rostoker

1978

J. geomagn. geoelec

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Recent observations of electric fields in the ionosphere using various measurement techniques have led to important advances in the understanding of magnetosphere-ionosphere coupling. In particular the discovery of evidence for parallel electric fields in the altitude range 2,000-10,000 km has an important impact on the question of auroral acceleration processes. More detailed mapping of large scale field-aligned current configurations on field lines penetrating the auroral oval are leading to more complete models for the generator processes in the outer magnetosphere which are associated with energy dissipation in the near-earth environment. Recent observations of significant electric fields equatorward of the auroral oval indicate that significant interaction between the magnetosphere and ionosphere takes place outside of the auroral oval. New techniques are presently being developed for more quantitative studies of magnetosphere-ionosphere coupling.

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The relationship between field-aligned currents and the auroral electrojets: A review

Kamide¹

1982

Space Sci Rev

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Observation of a structured auroral field-aligned current system

Cited by 13 publications

References 23 publications

The spatial relationship of field-aligned currents and auroral electrojets to the distribution of nightside auroras

The spatial relationship of field-aligned currents and auroral electrojets to the distribution of nightside auroras

Electric and magnetic fields in the ionosphere and magnetosphere.

The relationship between field-aligned currents and the auroral electrojets: A review

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