electron currents associated with an auroral band

Spiger, R. J.; Anderson, H. R.

doi:10.1029/ja080i016p02161

Cited by 26 publications

(10 citation statements)

References 10 publications

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“…The Rice University group has published a number of papers which present in situ useful data capable of testing any theoretical model of quiet auroral arcs [Vondrak et al, 1971;Park and Cloutier, 1971;Cloutier et al, 1973' Anderson andPazich and Anderson, 1975;Spiger and Anderson, 1975;Casserly and Cloutier, 1975;Sesiano and Cloutier, 1976 downward currents do not include auroral (-• 5 keV) electrons, upward currents consist of ambient electrons (<500 eV)and auroral electrons, though the latter contribution is often minor, say, 20%; (4) associated electrojets can either be westward or eastward; (5) arcs usually move equatorward with speeds of the order of 100 m s-X; (6) the field-aligned current intensity is of the order of 10 tzA/m 2, and the electrojet current is of the order of 10 a A; and (7) the arc width is typically 20 km, and the spacing, when it is multiple, is also about the same as the arc width. The underlying physics of the present feedback instability model is described elsewhere [Ogawa and Sato, 1971;Sato and Holzer, 1973].…”

Section: Introductionmentioning

confidence: 99%

A theory of quiet auroral arcs

Sato¹

1978

J. Geophys. Res.

212

222

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Being fed by the large‐scale magnetospheric convection, the coupled ionosphere‐magnetosphere system is subject to a feedback instability for a conjugate perturbation elongating in the east‐west direction, having a width of several tens of kilometers at the ionospheric level, standing along the magnetic field line. The growth time is as short as several minutes even when no hot electrons are involved in the field‐aligned current. Nonlinear development of the feedback instability is numerically investigated, taking hot electrons into account. The following conclusions are obtained. (1) An auroral arc can develop within a few tens of seconds once hot electrons take part. (2) The induced potential associated with the arc can reach several hundred volts. This predicts that the upward field‐aligned current may be provided by electrons with energies of the order of several hundred electron volts, provided anomalous resistivity or double layers develop. (3) The electron density enhancement is directly connected with the upward field‐aligned current and hence the auroral arc. (4) The downward current is localized equatorward of the upward current, when the background electric field is westward. (5) The electrojet current can grow to a few thousand amperes, which can either be westward or eastward, depending on the direction of the electric field. (6) The induced electric field inside the arc is almost constant and different from outside. These results are consistent with the observational results.

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Section: Introductionmentioning

confidence: 99%

A theory of quiet auroral arcs

Sato¹

1978

J. Geophys. Res.

212

222

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“…Anderson and P.A. Cloutier and colleagues have carried out detailed studies of rocket launch data involving passage through a discrete auroral arc in the evening sector (ANDERSON and CLOUTIER, 1975;PAZICH and ANDERSON, 1975;SPIGER and ANDERSON, 1975;CASSERLY and CLOUTIER, 1975). The arc lay near the poleward edge of an eastward electrojet.…”

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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“…In certain isotropic regions such as near T + 250 the pitch angle distribution was slightly peaked near 600-70 ø , dropping rapidly from 75 ø to 90 ø .It is striking that variations of flux in the highest energy interval ( 10-20 keY) preceded the variations of all lower energies by •9 s (•7.5 km). Since variations in lower energy intervals coincided very well, the offset cannot be due to dispersion in arrival time from a single localized source some distance from by these electrons and the ratios of precipitated to backscattered particles are discussed in the companion paper bySpiger and Anderson [1975].The energy flux carried into the atmosphere and scattered up from it has been calculated by integrating the measured spectra over pitch angle and energy, giving the amount plotted inFigure 8. In the interval T + 200-260 a maximum of 80% of the net downward flux is due to electrons in the 10-to 20-keV range, while an Upper limit to the energy above 20 keV is 9%, assuming a power law energy spectrum N(E) e,: E-" above 20 keV.…”

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confidence: 99%

Rocket measurement of auroral electron fluxes associated with field-aligned currents

Pazich¹,

Anderson

1975

J. Geophys. Res.

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A Nike‐Tomahawk rocket was instrumented with a vector magnetometer and an array of particle detectors including an electron and proton energy spectrometer covering the energy range 0.5–20 keV in seven fixed intervals and measuring the pitch angle distribution from 0° to 180° as the rocket spun. The payload was launched from Poker Flat, Alaska, at 0722 UT on February 25, 1972, over a bright auroral band that evidently was the poleward electron aurora, beyond the trapping boundary. An upper limit to the measured proton flux was 106/cm² s sr keV. The energy spectrum of the electron flux measured during passage over the visible aurora always exhibited a peak within the measured energy range. During passage over the brighter auroral forms the peak shifted from ∼3 to ∼10 keV, the pitch angle distribution became peaked along B, and the intensity increased. Maximum fluxes of ∼3 × 108 el/cm² s sr keV were seen over the aurora, which reached ∼60 kR of λ5577. The electron flux in regions of maximum flux tended to be the most field‐aligned in the energy interval showing the highest intensity.

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electron currents associated with an auroral band

Cited by 26 publications

References 10 publications

A theory of quiet auroral arcs

A theory of quiet auroral arcs

Electric and magnetic fields in the ionosphere and magnetosphere.

Rocket measurement of auroral electron fluxes associated with field-aligned currents

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