Dynamics of auroral belt and polar geomagnetic disturbances

Feldstein, Y. I.; Starkov, G. V.

doi:10.1016/0032-0633(67)90190-0

Cited by 448 publications

(234 citation statements)

References 17 publications

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“…In fact, they appear to follow the general location of the 0.7 keV peak locations as a function of local time. In Figure 12 it can be seen that the burst region is in general poleward of 740 at about 10 MLT and the auroral oval by Feldstein and Starkov (1967) is located at 74-76 at Q = 3. Qualitatively, therefore, the auroral arcs are located in the region of peaked precipitation of 0.7 keV at all local times -20 -from midnight to 10 MLT and the characteristics of the arcs may be related to the spectral structure of the peaks.…”

Section: Discussionmentioning

confidence: 98%

Latitude and local time dependence of precipitated low-energy electrons at high latitudes

Gustafsson¹

1973

J. Geophys. Res.

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Data from particle detectors on board the satellite Ogo 4 were used to study the precipitation of electrons in the energy range 0.7–24 kev. The latitude dependence of these particles in the local time region from midnight to dawn has been investigated in detail. The analysis shows that the precipitation of particles of energies 2.3–24 kev is centered at an invariant latitude of about 68° at midnight with a clear shift in latitude with increasing local time, and that this shift is more pronounced for lower energies. The highest fluxes of particles in this energy interval are measured at midnight, and they decrease rapidly with local time. In the dawn region, the location of the maximum precipitation for different energies varies about 1 ° of latitude for each unit of Kp, but the relative distribution remains almost unchanged. The fact that different energies have their maximums at different latitudes implies that the flux spectrum of precipitated particles, when measured at a certain latitude, has a peak at an energy corresponding to the energy of maximum precipitation at the latitude. The data in the energy range 2.3–24 kev support a theory in which particles are injected in the midnight region from the tail, gain energy owing to a betatron process, and then drift eastward in a combined electric and magnetic field. The main part of the electrons at 0.7 kev show a different behavior than do those at higher energies. They seem to undergo an acceleration process that is rather local, sometimes giving field‐aligned fluxes that may be superimposed on the background precipitation. The structural precipitation of 0.7‐kev electrons has been found to coincide on a statistical basis with the region of structural aurora indicating a relationship between the two phenomena.

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Section: Discussionmentioning

confidence: 98%

Latitude and local time dependence of precipitated low-energy electrons at high latitudes

Gustafsson¹

1973

J. Geophys. Res.

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“…1) and is assumed to be parallel to the convection reversal boundary. In a similar manner to scheme (i), the¯ow angle is determined from a fourthorder polynomial ®t to the range along each beam to the poleward wall of the auroral oval, based on the model of Feldstein and Starkov (1967) and Holzworth and Meng (1975). The¯ow angle determined in this way is illustrated in Fig.…”

Section: Discussionmentioning

confidence: 99%

“…Line-of-sight Doppler velocity is determined by a least-squares ®t to the phase (Feldstein and Starkov, 1967;Holzworth and Meng, 1975) of the complex value of the ACF as a function of lag. The elevation angle of backscatter can be determined from an interferometric analysis of the return backscatter, a phase di erence being determined from the crosscorrelation function of the signals received at the main and interferometer arrays [described more fully in Milan et al (1997a)].…”

Section: The Cutlass Coherent Hf Radarsmentioning

confidence: 99%

Simultaneous observations at different altitudes of ionospheric backscatter in the eastward electrojet

Milan

Lester

1998

Ann. Geophys.

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Abstract. A common feature of evening near-range ionospheric backscatter in the CUTLASS Iceland radar ®eld of view is two parallel, approximately L-shellaligned regions of westward¯ow which are attributed to irregularities in the auroral eastward electrojet region of the ionosphere. These backscatter channels are separated by approximately 100±200 km in range. The orientation of the CUTLASS Iceland radar beams and the zonally aligned nature of the¯ow allows an approximate determination of¯ow angle to be made without the necessity of bistatic measurements. The twō ow channels have di erent azimuthal variations in¯ow velocity and spectral width. The nearer of the two regions has two distinct spectral signatures. The eastern beams detect spectra with velocities which saturate at or near the ion-acoustic speed, and have low spectral widths (less than 100 m s À1 ), while the western beams detect lower velocities and higher spectral widths (above 200 m s À1 ). The more distant of the two channels has only one spectral signature with velocities above the ionacoustic speed and high spectral widths. The spectral characteristics of the backscatter are consistent with Eregion scatter in the nearer channel and upper-E-region or F-region scatter in the further channel. Temporal variations in the characteristics of both channels support current theories of E-region turbulent heating and previous observations of velocity-dependent backscatter cross-section. In future, observations of this nature will provide a powerful tool for the investigation of simultaneous E-and F-region irregularity generation under similar (nearly co-located or magnetically conjugate) electric ®eld conditions.

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“…Ionograms from the dynasonde located at the EISCAT facility in Tromsù, Norway (approximately collocated with beam 5, range gate 17 of the Finland radar ®eld-of-view), provide the diurnal variation of the ionospheric electron density pro®le at the solstices and (Feldstein and Starkov, 1967;Holzworth and Meng, 1975).…”

Section: Ionospheric Parameters As a Function Of Season: The Tromsù Dmentioning

confidence: 99%

“…3 illustrates the diurnal variation in the locations of the sub-auroral, auroral and polar cap ionospheric regions with respect to the 16 summary points of each radar, for three levels of geomagnetic activity, quanti®ed by the index K p . The auroral oval model employed is the statistical location of discrete optical emissions (Feldstein and Starkov, 1967;Holzworth and Meng, 1975).…”

Section: Introductionmentioning

confidence: 99%

Initial backscatter occurrence statistics from the CUTLASS HF radars

et al. 1997

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Abstract. A statistical study of the occurrence of ground and ionospheric backscatter within the ®elds-of-view of the CUTLASS HF radars, at an operating frequency of 10 MHz, during the ®rst 20 months of operation has been undertaken. The diurnal variation of the occurrence of backscatter and the range at which such backscatter is observed is found to be highly dependent on seasonal changes of the ionospheric electron density in both the E and F region, determined from ionosonde observations. In general, ionospheric backscatter is observed at far ranges during the local day in winter months and at near ranges during the local night in summer months. The Iceland radar observes more nearrange E region backscatter than the Finland radar as a consequence of its more zonal look-direction. The dependence of the occurrence of backscatter on geomagnetic activity and radar operating frequency are also investigated. The occurrence of ground and ionospheric backscatter is discussed in terms of HF propagation modes and ionospheric electron densities as well as geophysical processes. A brief assessment of the possible impact of solar cycle variations on the observations is made and frequency management is discussed. Such a study, with its focus on the`instrumental' aspect of backscatter occurrence, is essential for a full interpretation of HF coherent radar observations.

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Dynamics of auroral belt and polar geomagnetic disturbances

Cited by 448 publications

References 17 publications

Latitude and local time dependence of precipitated low-energy electrons at high latitudes

Latitude and local time dependence of precipitated low-energy electrons at high latitudes

Simultaneous observations at different altitudes of ionospheric backscatter in the eastward electrojet

Initial backscatter occurrence statistics from the CUTLASS HF radars

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