Excitation of twin-vortex flow in the nightside high-latitude ionosphere during an isolated substorm

Grocott, Adrian; Cowley, S. W. H.; Sigwarth, J. B.; Watermann, J.; Yeoman, T. K.

doi:10.5194/angeo-20-1577-2002

Cited by 54 publications

(77 citation statements)

References 63 publications

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“…This is despite the average IMF B z component becoming increasingly less negative from ∼5 min before substorm onset until ∼4 min after substorm onset. Such enhancement in the total transpolar flux associated with substorm onset was previously observed by Grocott et al (2002) while studying an isolated substorms. The transpolar voltages derived by Grocott and co-workers (2002) are very similar to the voltage magnitudes presented here.…”

Section: Discussionsupporting

confidence: 49%

“…Fast flows appear to be deflected around this suppressed flow region, in such a manner that the basic two-cell convection pattern was preserved. Previous workers have also observed regions of nightside flow suppression when studying the ionospheric response to a substorm expansion phase, for example, Yeoman et al (2000a), Fox et al (2001), Khan et al (2001) and Grocott et al (2002). It is likely that this suppressed flow region is related to the increased auroral and magnetic activity previously reported during the substorm expansion phase.…”

Section: Discussionmentioning

confidence: 85%

“…However, such an enhancement of the deflected flow would not affect the overall transpolar voltage . Grocott et al (2002) using the SuperDARN HF radars have demonstrated the excitation of large-scale flow associated with the substorm expansion phase of a small high-latitude substorm. The excited flow pattern was of a twin-vortex form with foci located at either end of the subsorm auroral bulge.…”

Section: Introductionmentioning

confidence: 99%

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Statistical study of high-latitude plasma flow during magnetospheric substorms

et al. 2004

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Abstract.We have utilised the near-global imaging capabilities of the Northern Hemisphere SuperDARN radars, to perform a statistical superposed epoch analysis of high-latitude plasma flows during magnetospheric substorms. The study involved 67 substorms, identified using the IMAGE FUV space-borne auroral imager. A substorm co-ordinate system was developed, centred on the magnetic local time and magnetic latitude of substorm onset determined from the auroral images. The plasma flow vectors from all 67 intervals were combined, creating global statistical plasma flow patterns and backscatter occurrence statistics during the substorm growth and expansion phases. The commencement of the substorm growth phase was clearly observed in the radar data 18-20 min before substorm onset, with an increase in the anti-sunward component of the plasma velocity flowing across dawn sector of the polar cap and a peak in the dawnto-dusk transpolar voltage. Nightside backscatter moved to lower latitudes as the growth phase progressed. At substorm onset a flow suppression region was observed on the nightside, with fast flows surrounding the suppressed flow region. The dawn-to-dusk transpolar voltage increased from ∼40 kV just before substorm onset to ∼75 kV 12 min after onset. The low-latitude return flow started to increase at substorm onset and continued to increase until 8 min after onset. The velocity flowing across the polar-cap peaked 12-14 min after onset. This increase in the flux of the polar cap and the excitation of large-scale plasma flow occurred even though the IMF B z component was increasing (becoming less negative) during most of this time. This study is the first to statistically prove that nightside reconnection creates magnetic flux and excites high-latitude plasma flow in a similar way to dayside reconnection and that dayside and nightside reconnection, are two separate time-dependent processes.

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Section: Discussionsupporting

confidence: 49%

Section: Discussionmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 99%

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Statistical study of high-latitude plasma flow during magnetospheric substorms

et al. 2004

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“…The expansion of the SuperDARN network allowed for the study of these larger-scale substorm-associated flows. Analyses of SuperDARN convection flows, obtained during isolated substorms, found evidence for the excitation of twin-vortex flow cells centred in the nightside ionosphere, which enhance the transpolar voltage by *40 kV compared with pre-onset values (Grocott et al 2000(Grocott et al , 2002. This is illustrated in Fig.…”

Section: Substorm Expansion Phasementioning

confidence: 73%

A decade of the Super Dual Auroral Radar Network (SuperDARN): scientific achievements, new techniques and future directions

et al. 2007

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The Super Dual Auroral Radar Network (SuperDARN) has been operating as an international co-operative organization for over 10 years. The network has now grown so that the fields of view of its 18 radars cover the majority of the northern and southern hemisphere polar ionospheres. SuperDARN has been successful in addressing a wide range of scientific questions concerning processes in the magnetosphere, ionosphere,

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“…Morelli et al, 1995;Yeoman et al, 2000) may play a role. More recently, Grocott et al (2002) presented an analysis of Super Dual Auroral Radar Network (SuperDARN) flow data obtained during an isolated substorm, and found evidence for the excitation of twin-vortex flow cells centred in the nightside ionosphere, which enhance the transpolar voltage by ∼40 kV compared with pre-onset values. Further studies using SuperDARN have produced mixed results, however, by providing evidence for both the excitation (e.g.…”

Section: Introductionmentioning

confidence: 99%

Superposed epoch analysis of the ionospheric convection evolution during substorms: onset latitude dependence

et al. 2009

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Abstract. Using data from the Super Dual Auroral Radar Network (SuperDARN) we investigate the ionospheric convection response to magnetospheric substorms. Substorms were identified using the Far Ultraviolet (FUV) instrument on board the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft, and were then binned according to the magnetic latitude of their onset. A superposed epoch analysis of the ionospheric convection patterns for each onset-latitude bin was then performed using radar data for the interval 60 min before onset to 90 min after. It is found that lower onset-latitude substorms are associated with generally more enhanced convection than the higher latitude substorms, although they suffer from a significant localised reduction of the flow in the midnight sector during the expansion phase. Higher-latitude substorms are associated with a significant and rapid increase in the nightside convection following substorm onset, with all onset-latitude bins showing an enhancement over onset values by ∼60 min into the expansion phase. A rudimentary inspection of the concurrent auroral evolution suggests that the duration of the flow reduction following substorm onset is dependent on the strength and duration of the expansion phase aurora and its associated conductivity enhancement.

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Excitation of twin-vortex flow in the nightside high-latitude ionosphere during an isolated substorm

Cited by 54 publications

References 63 publications

Statistical study of high-latitude plasma flow during magnetospheric substorms

Statistical study of high-latitude plasma flow during magnetospheric substorms

A decade of the Super Dual Auroral Radar Network (SuperDARN): scientific achievements, new techniques and future directions

Superposed epoch analysis of the ionospheric convection evolution during substorms: onset latitude dependence

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