Observations of two complete substorm cycles during the Cassini Earth swing‐by: Cassini magnetometer data in a global context

Khan, H.; Cowley, S. W. H.; Колесникова, Е. В.; Lester, M.; Brittnacher, M.; Hughes, T. J.; Hughes, W. J.; Kŭrth, W. S.; McComas, D. J.; Newitt, L R; Owen, C. J.; Reeves, G. D.; Singer, H. J.; Smith, Charles W.; Southwood, D. J.; Watermann, J.

doi:10.1029/2001ja900049

Cited by 19 publications

(25 citation statements)

References 44 publications

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“…We infer that the flow was diverted around this region due to the high electrical conductivity resulting from the precipitation. Similar effects have been found in previous studies by Kirkwood et al (1988), Morelli et al (1995), Yeoman et al (2000), and Khan et al (2001). Looking now at the magnetic observations, and identifying the west coast Greenland stations which lie within the meridian of the substorm bulge (see Fig.…”

Section: Vis Uv Earth Camera Auroral Images and Magnetic Disturbance supporting

confidence: 63%

“…(c) Flow suppression within and deflection around the dipolarized region (the blob of brightest auroral emission) occurred during the expansion phase, as observed in previous studies by Morelli et al (1995), Yeoman et al (2000), and Khan et al (2001). However, in the present case, the region effected was relatively small and localized near midnight, such that this represented a distinct but secondary effect.…”

Section: Discussioncontrasting

confidence: 49%

“…They suggest, however, that diversion of the twin-vortex flow around the low-flow high-conductivity auroral bulge formed during the expansion phase (e.g. Kirkwood et al, 1988;Morelli et al, 1995;Yeoman et al, 2000;Khan et al, 2001) may play a role. Fox et al (1999) have also reported observations of a surge of transpolar flow into the midnight sector associated with a substorm intensification, which they suggest was due to a burst of reconnection in the tail.…”

Section: Introductionmentioning

confidence: 92%

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

et al. 2002

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Abstract. We present SuperDARN radar observations of the ionospheric flow during a well-observed high-latitude substorm which occurred during steady northward IMF conditions on 2 December 1999. These data clearly demonstrate the excitation of large-scale flow associated with the substorm expansion phase, with enhanced equatorward flows being observed in the pre-midnight local time sector of the expansion phase auroral bulge and westward electrojet, and enhanced return sunward flows being present at local times on either side, extending into the dayside sector. The flow pattern excited was thus of twin-vortex form, with foci located at either end of the substorm auroral bulge, as imaged by the Polar VIS UV imager. Estimated total transpolar voltages were ∼40 kV prior to expansion phase onset, grew to ∼80 kV over a ∼15 min interval during the expansion phase, and then decayed to ∼35 kV over ∼10 min during recovery. The excitation of the large-scale flow pattern resulted in the development of magnetic disturbances which extended well outside of the region directly disturbed by the substorm, depending upon the change in the flow and the local ionospheric conductivity. It is estimated that the nightside reconnection rate averaged over the 24-min interval of the substorm was ∼65-

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Section: Vis Uv Earth Camera Auroral Images and Magnetic Disturbance supporting

confidence: 63%

Section: Discussioncontrasting

confidence: 49%

Section: Introductionmentioning

confidence: 92%

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

et al. 2002

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“…Science analysis of the magnetic field data from the flyby has resulted in numerous publications clearly highlighting the instrument's performance in detection of magnetic phenomena in a planetary environment. Due to the very high flyby speed (∼16 km/sec) and the high time resolution of the magnetic field observations (32 vectors/sec) significant new information was obtained on a variety of topics including possible evidence of the plasmasphere interchange instability (see Khan et al, 2001;Smith et al, 2001;Southwood et al, 2001;Tsurutani et al, 2001). …”

Section: Earth Swingbymentioning

confidence: 99%

The Cassini Magnetic Field Investigation

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Kellock

Southwood

et al. 2004

The Cassini-Huygens Mission

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Abstract. The dual technique magnetometer system onboard the Cassini orbiter is described. This instrument consists of vector helium and fluxgate magnetometers with the capability to operate the helium device in a scalar mode. This special mode is used near the planet in order to determine with very high accuracy the interior field of the planet. The orbital mission will lead to a detailed understanding of the Saturn/Titan system including measurements of the planetary magnetosphere, and the interactions of Saturn with the solar wind, of Titan with its environments, and of the icy satellites within the magnetosphere.

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“…The electric field within this auroral bulge is found to be strongly suppressed (e.g. Morelli et al, 1995;Yeoman et al, 2000a,b;Khan et al, 2001;Cowley et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

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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Observations of two complete substorm cycles during the Cassini Earth swing‐by: Cassini magnetometer data in a global context

Cited by 19 publications

References 44 publications

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

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

The Cassini Magnetic Field Investigation

Statistical study of high-latitude plasma flow during magnetospheric substorms

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