Global observations of substorm injection region evolution: 27 August 2001

Spanswick, E.; Donovan, E.; Liu, W.; Liang, J.; Blake, J. B.; Reeves, G. D.; Friedel, R. H. W.; Jackel, B. J.; Cully, C. M.; Weatherwax, A. T.

doi:10.5194/angeo-27-2019-2009

Cited by 15 publications

(13 citation statements)

References 14 publications

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“… Liu et al [2009b] observed magnetic field dipolarization signatures at ∼−11 R E to occur ∼90 s after tail reconnection signatures at ∼−20 R E . Spanswick et al [2009] studied a substorm on 27 August 2001 in detail, concluding that the magnetic field pulse took ∼8 min to propagate from −18 to −6.6 R E . Spanswick et al [2009] also reported that EEPs were observed on the ground near L = 6.6 and expanded both poleward and equatorward, consistent with the earlier riometer‐based survey of Berkey et al [1974].…”

Section: Introductionmentioning

confidence: 99%

Combined THEMIS and ground‐based observations of a pair of substorm‐associated electron precipitation events

Clilverd¹,

Rodger²,

Rae³

et al. 2012

J. Geophys. Res.

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.[1] Using ground-based subionospheric radio wave propagation data from two very low frequency (VLF) receiver sites, riometer absorption data, and THEMIS satellite observations, we examine in detail energetic electron precipitation (EEP) characteristics associated with two substorm precipitation events that occurred on 28 May 2010. In an advance on the analysis undertaken by Clilverd et al. (2008), we use phase observations of VLF radio wave signals to describe substorm-driven EEP characteristics more accurately than before. Using a >30 keV electron precipitation flux of 5.6 Â 10 7 el. cm À2 sr À1 s À1and a spectral gradient consistent with that observed by THEMIS, it was possible to accurately reproduce the peak observed riometer absorption at Macquarie Island (L = 5.4) and the associated NWC radio wave phase change observed at Casey, Antarctica, during the second, larger substorm. The flux levels were near to 80% of the peak fluxes observed in a similar substorm as studied by Clilverd et al. (2008). During the initial stages of the second substorm, a latitude region of 5 < L < 9 was affected by electron precipitation. Both substorms showed expansion of the precipitation region to 4 < L < 12 more than 30 min after the injection. While both substorms occurred at similar local times, with electron precipitation injections into approximately the same geographical region, the second expanded in an eastward longitude more slowly, suggesting the involvement of lower-energy electron precipitation. Each substorm region expanded westward at a rate slower than that exhibited eastward. This study shows that it is possible to successfully combine these multi-instrument observations to investigate the characteristics of substorms.

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Section: Introductionmentioning

confidence: 99%

Combined THEMIS and ground‐based observations of a pair of substorm‐associated electron precipitation events

Clilverd¹,

Rodger²,

Rae³

et al. 2012

J. Geophys. Res.

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“…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%

“…Substorm injections are often dispersionless [McIlwain, 1974;Mauk and Meng, 1987] and are contained within a localized injection region characterized by a well-defined injection boundary at its edges [Reeves et al, 1991]. It has been shown that dipolarization and injection signatures are localized at substorm onset, and expand azimuthally [Thomsen et al, 2001] and radially [Spanswick et al, 2009] during the substorm's expansion phase. Azimuthal and radial expansion of the dipolarization fronts have been studied in detail using geosynchronous magnetic field data [Liou et al, 2002;Watson and Jayachandran, 2009].…”

Section: Introductionmentioning

confidence: 99%

“…[3] Sudden absorption increase events associated with substorms have been extensively studied using riometer absorption data from auroral regions [Hargreaves, 1974;Ranta et al, 1981;Hajkowicz, 1990;Ranta and Yamagishi, 1997;Spanswick et al, 2009]. The sharp rise in absorption is interpreted as the sudden onset of high energy particle precipitation into the ionosphere due to sudden enhancement of high energy particle flux in the plasma sheet associated with the substorm expansion phase.…”

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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“…This event has been already studied (Baker et al 2002;Li et al 2003;Eriksson et al 2004;Blake et al 2005;Spanswick et al 2009;Mishin et al 2012). We complement and expand on the previous results, thoroughly analyzing the role of the induction mechanism.…”

Section: Introductionmentioning

confidence: 99%

Strong induction effects during the substorm on 27 August 2001

Мишин

Lunyushkin

et al. 2015

Earth Planet Sp

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We report on strong induction effects notably contributing to the cross polar cap potential drop and the energy balance during the growth and active phases of the substorm on 27 August 2001. The inductance of the magnetosphere is found to be crucial for the energy balance and electrical features of the magnetosphere in the course of the substorm. The inductive response to the switching on and off of the solar wind-magnetosphere generator exceeds the effect of the interplanetary magnetic field (IMF) variation. The induction effects are most apparent during the substorm expansion onset when the rapid growth of the ionospheric conductivity is accompanied by the fast release of the magnetic energy stored in the magnetotail during the growth phase. Using the magnetogram inversion technique, we estimated the magnetospheric inductance and effective ionospheric conductivity during the loading and unloading phases.

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Global observations of substorm injection region evolution: 27 August 2001

Cited by 15 publications

References 14 publications

Combined THEMIS and ground‐based observations of a pair of substorm‐associated electron precipitation events

Combined THEMIS and ground‐based observations of a pair of substorm‐associated electron precipitation events

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

Strong induction effects during the substorm on 27 August 2001

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