A synoptic investigation of particle precipitation dynamics for 60 substorms in IQSY (1964–1965) and IASY (1969)

Berkey, F. T.; Driatskiy, V. M.; Henriksen, K.; Hultqvist, B.; Jelly, Doris H.; Shchuka, T. I.; Theander, A.; Ylindemi, J.

doi:10.1016/0032-0633(74)90028-2

Cited by 98 publications

(129 citation statements)

References 32 publications

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“…The highest speed was observed near the lowest latitude stations, while higher latitude results were all less than 0.7 km/s. Berkey et al [1974] found poleward expansion speeds of 0.3-1.9 km/s from observations of 26 substorm events at stations between 57°and 76°magnetic latitude. A tendency for speeds to decrease above 71°magnetic latitude was also reported.…”

Section: Discussionmentioning

confidence: 82%

“…For a number of events, they found that a sharp rise in plasma sheet electron flux for energies >30 keV (dispersionless injection) was often accompanied (under certain conditions) by a sharp rise in riometer absorption due to sudden enhancement of ionization in the lower ionosphere. If multiple riometers pick up this ionospheric signature of high energy particle precipitation, then tracking the movement of these signatures can give insight into the spatial and temporal evolution of the substorm injection region [Berkey et al, 1974;Liang et al, 2007;Liu et al, 2007;Spanswick et al, 2009]. In this study, we extend this ground-based method of identifying substorm precipitation signatures to GPS TEC, assuming that enhanced electron density due to high-energy particle precipitation will produce detectable TEC enhancements.…”

Section: Introductionmentioning

confidence: 99%

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GPS TEC technique for observation of the evolution of substorm particle precipitation

et al. 2011

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[1] One of the signatures of magnetospheric substorms is the precipitation of high energy particles into the high latitude ionosphere. In this paper, we introduce a new method of tracking substorm particle precipitation using GPS Total Electron Content (TEC) and provide some preliminary observations of precipitation signatures from application of this method. Using TEC measurements from several GPS receivers, we examined particle precipitation signatures associated with two separate substorm events (4 October 2008 and 29 October 2008) and monitored the expansion of the high energy precipitation regions with a higher temporal and spatial resolution than previously available. For each event we have observed TEC signatures associated with substorm particle precipitation along 20 to 25 separate GPS raypaths from up to 7 GPS receivers located in the Canadian Arctic. This is in addition to particle injection signatures found in CLUSTER satellite data and precipitation signatures in ground based riometer data. Signature timing on different raypaths from different stations indicates a mainly northward (tailward) expansion of the precipitation (injection) region with a smaller westward (azimuthal) component for the events studied. By applying a triangulation method, we also calculated propagation velocity of the precipitation boundary in regions covered by our GPS receivers. For each substorm, expansion velocity ranged from 0.3-2 km/s northward and 0-1 km/s westward, and tended to decrease in magnitude at higher latitudes.

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Section: Discussionmentioning

confidence: 82%

Section: Introductionmentioning

confidence: 99%

GPS TEC technique for observation of the evolution of substorm particle precipitation

et al. 2011

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“…Hargreaves, 1970;Berkey et al, 1974;Nielsen, 1980;Stauning et al, 1995;Kainuma et al, 2001;del Pozo et al, 2002, and references therein). Berkey et al (1974), by considering a large number of synoptic absorption maps from over 40 riometer stations in the subauroral, auroral, and polar cap latitudes during substorm conditions, concluded that the absorption maxima in most cases moved eastward from the substorm injection area with a velocity of 0.7-7 km/s, consistent with the idea that the motion of auroral particles injected during the substorm into the nightside ionosphere is governed by gradient-curvature (GC) drift. Hargreaves (1970), using the absorption data from 4 closely-spaced riometers, found a significantly lower (from 80 m/s to 3.3 km/s) range of velocities of eastward expansion with a significant number of absorption events expanding westward.…”

Section: Introductionmentioning

confidence: 99%

Imaging riometer observations of drifting absorption patches in the morning sector

et al. 2004

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Abstract.Observations by a 7×7-beam imaging riometer in Kilpisjärvi, Finland (∼66 • MLAT) of the drifting cosmic noise absorption (CNA) structures in the morning sector near the zonal drift reversals are presented. The examination of the absorption intensity images revealed several regions with enhanced CNA (absorption patches) slowly drifting through the riometer field of view (FoV). The absorption patches were found to vary in shape, orientation (for elongated arc-like patches), and drift direction. The latter was calculated from the regression lines to positions of the absorption maxima in the FoV images and compared with the direction of electrojet plasma flow from horizontal magnetic perturbations and (for one event) tristatic ion drift velocities in the F-region. A reasonable agreement was found between these directions both in point-by-point comparisons and in terms of direction reversal timings. The absorption patches of lower intensity appear to have smaller drift velocities and to be associated with weaker magnetic perturbations. These results are consistent with the notion that relatively slow motions of the auroral absorption near the zonal drift reversals are associated with the E×B drift of the entire magnetic flux tube as opposed to the gradient-curvature drift of energetic electrons injected into the ionosphere at the substorm onset. The absorption drift velocity magnitude, on the other hand, was found to be substantially lower than that of the plasma flow based on the results of limited comparison with tristatic ion drift measurements. A comparison of the drift directions with those of the patch elongation showed that a considerable number of patches had these directions close to each other. Using this observation, we demonstrate a satisfactory agreement between the patch drift velocities (both in direction and magnitude) as determined from the absorption images and keograms under the assumption that some patches were propagating in a direction that was significantly different from the perpendicularity to elongation.

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“…This makes it ideal for the study of the intense and rapidly varying absorption which is induced primarily by high-energy electron precipitation in the auroral regions, and it is on this area of research that the majority of these instruments have been focused. Networks of riometers in the polar regions have enabled the general morphology of the auroral substorm to be defined [Berkey et al, 1974] [Hargreaves and Jarvis, 1986]. In 1998 an imaging riometer system operating at a frequency of 38.2 MHz was deployed at Halley alongside this wide-beam array, necessitating the construction of an array of 64 crossed-dipole antennas and a ground plane.…”

Section: Introductionmentioning

confidence: 99%

The effect of snow accumulation on imaging riometer performance

Rose¹,

Jarvis²,

Clilverd³

et al. 2000

Radio Science

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Abstract. In January 1998 an imaging riometer system was deployed at Halley, Antarctica (76øS, 27øW), involving the construction of an array of 64 crossed-dipole antennas and a ground plane. Weather conditions at Halley mean that such an array will rapidly bury beneath the snow, so the system was tuned to operate efficiently when buried. Theoretical calculations indicate that because the distance between the ground plane and the array was scaled to be 1/4A in the snow, as snow fills the gap the signal will increase by 0.6-2.5 dB. Similarly, the short antennas are resonant when operated in snow, not in air. Theoretical calculations show that the largest effect of this is the mismatch of their feed point impedance to the receiver network. As the signal for each riometer beam is composed of a contribution from all 64 antennas, for each antenna that buries the signal level will increase by 1/64 of •09 dB. The measured response of the system to burial showed significant changes as snow accumulated in and over the array during 1998. The changes are consistent with the magnitude of the effects predicted by the theoretical calculations. The Halley imaging riometer system, having now been buried completely, is operating more efficiently than if a standard air-tuned configuration had been deployed. The results are of considerable relevance to the ever-increasing community of imaging riometer users regarding both deployment and the subsequent interpretation of scientific data. Some systems will experience similar permanent burial, while others will be subject to significant annual variability as a result of becoming snow-covered during winter and (:lear during summer.

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A synoptic investigation of particle precipitation dynamics for 60 substorms in IQSY (1964–1965) and IASY (1969)

Cited by 98 publications

References 32 publications

GPS TEC technique for observation of the evolution of substorm particle precipitation

GPS TEC technique for observation of the evolution of substorm particle precipitation

Imaging riometer observations of drifting absorption patches in the morning sector

The effect of snow accumulation on imaging riometer performance

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