The occurrence and properties of large-scale electron-density structures in the auroral F region

Burns, Christopher J.; Hargreaves, J. K.

doi:10.1016/0021-9169(95)00031-3

Cited by 4 publications

(3 citation statements)

References 19 publications

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“…The resulting luminous patches were about 100 km across. Spatial structures in the high‐latitude F region with dimensions of tens of kilometers, drifting with the convection pattern, have been observed by incoherent scatter radar [ Hargreaves et al , ; Burns and Hargreaves , ].…”

Section: Fine Structure Within Passes and Implicationsmentioning

confidence: 99%

Variability and spatial fine structure of precipitating and trapped medium‐energy electron fluxes in the noon sector

Hargreaves

Birch

Evans³

2014

JGR Space Physics

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Key Points:• Spatial fine structure and causes of electron precipitation in the noon sector • Derived relationships between the trapped and precipitating electrons • Properties are compared for electron energies exceeding 30 keV and 100 keV AbstractThe relationships between the precipitating and trapped components of magnetospheric electron flux for energy ranges exceeding 30 and 100 keV have been investigated using data from polar orbiting satellites, the study being restricted to a limited geographic region at auroral latitudes in the noon sector. The electron flux of these energies is the cause of auroral radio absorption. The data are analyzed at two levels of detail. Variations between different passes are studied using their median values, and variations within passes are derived from individual data points at 2 s intervals, equivalent to about 10 km in distance. Several types of behavior are recognized. Basically, the ratio of precipitating to trapped flux at energies exceeding 30 keV varies in proportion to the trapped flux, though there is a limiting upper value where the two components are approximately equal. The precipitating flux never exceeds the trapped flux by any significant amount. These types appear to be consistent with weak and strong pitch angle scatterings, respectively. The precipitation at >100 keV varies somewhat with the >100 keV trapped flux but more strongly with the >30 keV component, consistent with scattering by chorus waves produced by electrons less energetic than those being scattered. Comparison between the two energy ranges shows that the precipitating component is always softer than the trapped. The detailed relationship between the precipitating and trapped components varies from pass to pass by an amount related to the east-west component of the interplanetary magnetic field. Superimposed on the above behavior are large reductions of precipitation, spatial rather than temporal in nature, during which the trapped flux remains virtually unchanged. These reductions appear to be due to structures some tens of kilometers across, perhaps related to "ducts" within the magnetosphere. Some theoretical considerations based on the Kennel and Petscheck theory of scattering are given in an Appendix.

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Section: Fine Structure Within Passes and Implicationsmentioning

confidence: 99%

Variability and spatial fine structure of precipitating and trapped medium‐energy electron fluxes in the noon sector

Hargreaves

Birch

Evans³

2014

JGR Space Physics

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“…The irregularities can be classified into three groups according to size, (a) small‐scale (<100 m); (b) intermediate‐scale (0.1–10 km) (c) large‐scale (>10 km) [ Vickrey and Kelley , 1983]. Small and intermediate‐scale irregularities cause phase and amplitude scintillations by a diffraction mechanism [ Burns and Hargreaves , 1996; Hunsucker and Hargreaves , 2003]. In this study we are mainly concerned with large irregularity structures.…”

Section: Ionospheric Irregularity Modelsmentioning

confidence: 99%

Ionospheric structure effects on HF radio wave propagation for the Enhanced Polar Outflow Probe (e‐POP) satellite mission

2004

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[1] The Enhanced Polar Outflow Probe (e-POP) payload will be launched on a small satellite in 2007 for exploring plasma and atmospheric outflow process in the polar region. The subject of this paper is whether one can determine the properties of large-scale ionospheric structures by studying the perturbations that they cause on HF radio waves received at the e-POP satellite from ground-based transmitters such as the Canadian Advanced Digital Ionosonde (CADI). The perturbations on the received waves have been investigated using numerical ray-tracing methods. These simulation results show that ionospheric irregular structures lead to a complex pattern of amplitude, propagation time delay, Doppler frequency, and direction-of-arrival (DOA) effects on the HF radio waves received at the satellite. The simulations also show that ionospheric density structure cannot be measured unambiguously using a single wave property. Therefore a ''catalog'' of HF signatures of typical ionospheric irregularities has been established in order to be able to interpret the e-POP HF measurements in terms of ionospheric structures.

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“…Ever since 1970 when the first ionospheric heating device Platteville was built up in Boulder (40.18 • N, 104.73 • W) in America, many other ionospheric modification devices have been established step by step in the other places including HIPAS (and later HAARP) in America, SURA in Russia and Tromsø from European EISCAT, etc. With these powerful facilities, lots of valuable experimental results were obtained such as the primary spatio-temporal effect [1,2] and the secondary spatio-temporal effect [3∼5] of the heating experiments.…”

Section: Introductionmentioning

confidence: 99%

Research of Ionospheric Instability Excited in Mid and Low Latitudes HF Heating

Ding¹,

Zhao²,

Zhou³

et al. 2010

Chinese J of Geophysics

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The results of 2D simulation of ionospheric HF pump heating indicate that although the simulation results are affected by the background ionospheric conditions, the electron density and temperature tend towards stationary after heating simulation begins under most undisturbed circumstance. This result is proved by many experiments. Nevertheless on occasion the temporal and spatial distribution of the electron density and temperature near the reflection region of HF pump waves appear to be instable after turning on/off the HF heating equipment. This phenomenon is simulated and interpreted in this paper. The excitation of this instability is explained by a positive feedback mechanism as follows, when the electron temperature is heating up by the pump waves, the reduction of electron density in this region is generated by the plasma expansion. The electron energy decreases in the electron energy equation due to the collision between electron and ion which is influenced by the electron temperature and density. In consequence the positive feedback mechanism is set up as a result of electron temperature increase. It can be concluded that a more obvious change of electron density and temperature in HF pump heating is generated by an instability mechanism if three conditions are satisfied, (1) an evident two-peak structure of ionospheric electron temperature; (2) a high electron temperature in the heated region; (3) electron and ion collision is the main proportion of the energy loss factor. These conditions are more easily to be satisfied in the afternoon.

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The occurrence and properties of large-scale electron-density structures in the auroral F region

Cited by 4 publications

References 19 publications

Variability and spatial fine structure of precipitating and trapped medium‐energy electron fluxes in the noon sector

Variability and spatial fine structure of precipitating and trapped medium‐energy electron fluxes in the noon sector

Ionospheric structure effects on HF radio wave propagation for the Enhanced Polar Outflow Probe (e‐POP) satellite mission

Research of Ionospheric Instability Excited in Mid and Low Latitudes HF Heating

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