Top side ionospheric spread<i>F</i>and particle precipitation in the day side magnetospheric clefts

Dyson, P. L.; Winningham, J. D.

doi:10.1029/ja079i034p05219

Cited by 92 publications

(30 citation statements)

References 20 publications

(11 reference statements)

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“…It is possible that the precipitation is itself spatially structured on a sufficiently small scale to be responsible for the irregularities causing the backscatter. Dyson and Winningham [1974] showed that structure in the topside was generally collocated with the <300 eV electron precipitation and suggested that such correlation might indicate that the irregularities were produced directly by small‐scale structure within the precipitation itself. There is ample evidence of finer structure in the cusp region than the large‐scale gradient imaged here.…”

Section: Discussionmentioning

confidence: 99%

On the generation of cusp HF backscatter irregularities

et al. 2002

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[1] HF radar observations, 630.0 nm cusp auroral emission, and an ionospheric tomography scan are compared to investigate the mechanism by which radar cusp echoes are generated. A collocation is reported between the equatorward boundaries of broad spectral width HF radar backscatter and 630.0 nm cusp auroral precipitation. In addition, the radio tomographic image reveals spatial structures in ionospheric electron density that map closely to the precipitation. However, the large-scale horizontal gradient appears to be insufficiently steep to account alone for the rapid growth of irregularities by the gradient drift mechanism. It is proposed that the initial source of the decameter-scale features responsible for the backscatter may result from fine structure within the precipitation itself, or alternatively, from the cascade down of unstable intermediate-scale gradients created in the plasma convecting poleward from the source region. The latter process may explain the ongoing backscatter found poleward of the auroral band.

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Section: Discussionmentioning

confidence: 99%

On the generation of cusp HF backscatter irregularities

et al. 2002

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“…Both the Langmuir probe and the sounder indicate the region of intense particle fluxes to be coincident with a region of topside spread F, STIZ[Dyson and Winningham, 1974]. The major difference between the two results is one of spatial/ temporal resolution, the Langmuir probe having much greater resolution.…”

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confidence: 96%

A case study of the aurora, high‐latitude ionosphere, and particle precipitation during near‐steady state conditions

Winningham¹,

Anger²,

Shepherd³

et al. 1978

J. Geophys. Res.

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An Isis 2 pass is singled out for a detailed examination of the particle fluxes, optical emissions, and ionospheric parameters observed during a quiescent period (late recovery) between two substorms. This pass was chosen because it was part of a coordinated data acquisition period between the Air Force Geophysics Laboratory (AFGL) Airborne Ionospheric Observatory, Isis 2, and DMSP (Defense Meteorological Satellite Program). As a result, both long‐duration measurements (aircraft) and transient, snapshot (spacecraft) data are available. This allows, on a macroscopic level, the separation of space and time effects. On the basis of the joint data set it was established that the latitudinal morphology observed by the satellite is basically spatial in nature. It is concluded that the observed particle fluxes are most easily understood in terms of precipitation from the quiet time plasma sheet without intervening acceleration. The observed optical emissions and ionospheric parameters are found to be in good qualitative and quantitative agreement (within experimental error) with the electron fluxes, although establishment of this point has required careful determination of the viewing direction of the optical instruments, removal of scattered light (albedo) from underlying cloud and snow, and consideration of the effects of photon‐counting statistics on contour plots of the optical data.

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“…The peculiar feature of this pass is the irregular structure of the electron density at frame numbers 30 through 56, where the electron density largely varies from frame to frame. The corresponding ionograms exhibit severe backscattering signals near the zero range indicating large amplitude irregularities [ Dyson and Winningham , 1974]. A detailed analysis of the irregularities is beyond this paper but we discuss the validity of the ANN application for extraordinary cases.…”

Section: Resultsmentioning

confidence: 99%

Retrieval of in situ electron density in the topside ionosphere from cosmic radio noise intensity by an artificial neural network

Maruyama

2002

Radio Science

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An artificial neural network (ANN) is applied to retrieve electron density at satellite height from cosmic radio noise measurements made near the plasma cutoff frequency in the topside ionosphere. Observations were made using the topside sounder on board the Ionosphere Sounding Satellite launched in 1978. The automatic gain control voltage of the sounder receiver supplied information on the spectrum of cosmic radio noise intensity. Local electron densities, which are the target of the ANN, were scaled from the plasma resonance spikes and the echo traces in the ionogram for several passes. Each pass contained about 100 frames of ionograms; it is not a very easy task to scale the local plasma parameters by an eyeball judgment for all passes. With the aid of a neural network application, we determined the in situ electron density for about 150,000 ionograms. The results were applied to global ionospheric mapping.

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Top side ionospheric spreadFand particle precipitation in the day side magnetospheric clefts

Cited by 92 publications

References 20 publications

On the generation of cusp HF backscatter irregularities

On the generation of cusp HF backscatter irregularities

A case study of the aurora, high‐latitude ionosphere, and particle precipitation during near‐steady state conditions

Retrieval of in situ electron density in the topside ionosphere from cosmic radio noise intensity by an artificial neural network

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