Rocket-based magnetic observations of auroral birkeland currents in association with a structured auroral arc

Casserly, R. T.; Cloutier, P. A.

doi:10.1029/ja080i016p02165

Cited by 50 publications

(21 citation statements)

References 8 publications

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“…From vector ion measurements aboard Atmospheric Explorer C, they inferred the electric field pattern over the dayside high latitude region. They observed the usual electric field reversal across the auroras oval reported earlier by several authors (e.g., CAUFFMAN and GURNETT, 1971;HEPPNER, 1972), but they also noted that over most of the dayside cleft the electric field polarity change represented a shear reversal, viz, the electric field goes to zero at the point of reversal. Only near local noon, was it inferred that the electric field changed polarity by rotating through the dawn-to-dusk direction.…”

Section: High Latitude Electric Fieldsmentioning

confidence: 57%

“…In particular, CAUFFMAN and GURNETT (1971) and HEPPNER (1972) presented evidence leading to the definition of the electric field pattern in the high latitude ionosphere, while MOZER and LUCHT (1974) used balloon borne electric field probes to acquire a large body of data from which the diurnal variation of the auroral zone electric field was evaluated.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: High Latitude Electric Fieldsmentioning

confidence: 57%

Section: Introductionmentioning

confidence: 99%

Electric and magnetic fields in the ionosphere and magnetosphere.

Rostoker

1978

J. geomagn. geoelec

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“…Field-aligned (FA) currents in multiple auroral arcs at the nightside have been measured several times in rocket auroral magnetic field experiments (Casserly and Cloutier, 1975;Sesiano and Cloutier, 1976) while, until recently, they were only noted rarely from satellite magnetometer measurements (see however, Lanchester and Wallis 1985;Bythrow et al, 1986;Potemra et al 1987). In the 90s some prominent cases of multiple current sheets within the auroral oval were reported by Fukunishi et al, (1991); Obara et al, (1993) from AKEBONO satellite, Luhr et al, (1994) and Ohtani et al, (1994) from FREJA satellite.…”

Section: Introductionmentioning

confidence: 87%

“…The Romanian triaxial fluxgate magnetometer SGR-7 (see, Ciobanu et al, 1993) was initially conceived as a navigation device for the magnetically oriented MA-GION-2 and MAGION-3 subsatellites (Triska et al, 1990).…”

Section: Magion-and Magion-3 Magnetometer Experimentsmentioning

confidence: 99%

Multiple current sheets in a double auroral oval observed from the MAGION-2 and MAGION-3 satellites

et al. 1997

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Abstract. A case is described of multiple current sheets crossed by the MAGION-2 satellite in the near-midnight quieting auroral oval. The data were obtained by the magnetometer experiment onboard. Results show during a quieting period after a preceding substorm, or during an early growth phase of the next substorm, two double-sheet current bands, POLB and EQUB, located at respectively the polar and equatorial borders of the auroral oval separated by about 500 km in latitude. This is consistent with the double-oval structure during recovery introduced by Elphinstone et al. (1995). Within the POLB, the magnetic field data show simultaneous existence of several narrow parallel bipolar current sheets within the upward current branch (at 69.5-70.3°i nvariant latitude) with an adjacent downward current branch at its polar side at (70.5-71.3°). The EQUB was similarly stratified and located at 61.2-63.5°invariant latitude. The narrow current sheets were separated on average by about 35 km and 15 km, respectively, within the POLB and EQUB. A similar case of double-oval current bands with small-scale structuring of their upward current branches during a quieting period is found in the data from the MAGION-3 satellite. These observations contribute to the double-oval structure of the late recovery phase, and add a small-scale structuring of the upward currents producing the auroral arcs in the double-oval pattern, at least for the cases presented here. Other observations of multiple auroral current sheets and theories of auroral arc multiplicity are briefly discussed. It is suggested that multiple X-lines in the distant tail, and/or leakage of energetic particles and FA currents from a series of plasmoids formed during preceding magnetic activity, could be one cause of highly stratified upward FA currents at the polar edge of the quieting double auroral oval.

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“…However, it so happens that the physical parameters of the lower magnetosphere and upper ionosphere are such that both effects can be (and probably are) realized simultaneously, but at different altitudes. The existence of sufficiently strong field-aligned current densities above the auroral zone has been frequently verified (Casserly & Cloutier 1975;Iijima & Potemra 1976).…”

Section: Introductionmentioning

confidence: 99%

Acceleration from Field-Aligned Potential Drops

Haerendel

1994

International Astronomical Union Colloquium

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Unstable field-aligned currents are seen as the origin of field-aligned potential drops. They convert energy stored in magnetic shear stresses into kinetic energy. A good fraction of this energy is carried by runaway electrons and ions out of the acceleration region. The paper emphasizes the analogy with mechanical fractures. Simple expressions for the energy conversion rate and the parallel potential drop are derived, the two being linked by the critical current density needed for instability. The origin of the currents (generator) lies mostly in a region remote from that of energy conversion (fracture zone). The transmission of shear stresses and energy from the generator plasma, where the primary forces are applied to the fracture zone is also considered. A closed set of relations allows quantitative evaluation of the energetic particle production efficiency. The decoupling of the plasma on either side of the fracture zone which allows fast stress relief is described in detail, as well as a stationary model for the Alfven wave interaction between fracture zone and generator plasma. A simple concept of the nature of the anomalous resistivity generated by the unstable current leads to an expression for the magnetic diffusivity inside the fracture zone and an estimate of the latter's extent parallel to the magnetic field, whereas its width and length transverse to B follow from the macroscopic relations. Finally and as an example, the theory is applied to the problem of fast electron (and ion) acceleration well above 1 MeV seen to occur in many solar flares. It is obvious that this process belongs to the most powerful production processes of high-energy particles in stellar magnetic fields.

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Rocket-based magnetic observations of auroral birkeland currents in association with a structured auroral arc

Cited by 50 publications

References 8 publications

Electric and magnetic fields in the ionosphere and magnetosphere.

Electric and magnetic fields in the ionosphere and magnetosphere.

Multiple current sheets in a double auroral oval observed from the MAGION-2 and MAGION-3 satellites

Acceleration from Field-Aligned Potential Drops

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