Spatial distribution of conductances and currents associated with a north-south auroral form during a multiple-substorm period

Amm, O.; Pajunpää, A.; Brändström, U.

doi:10.1007/s005850050864

Cited by 17 publications

(32 citation statements)

References 29 publications

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“…Our observations are consistent with the previous findings associating auroral streamers (or north‐south auroras) with R1‐type current systems [ Amm et al , 1999]. The CCW vortex in EC vectors at the western flank of the streamer supports this conclusion as well as the spatial distribution of electron and proton auroras, former (latter) concentrating to the western (eastern) flank of the streamer (cf.…”

Section: Discussionsupporting

confidence: 93%

“…In the region of auroras ECs can be assumed to be large as the ionospheric conductivity is high there. Observing equally large ECs in the dark dawnside flank implies strong electric field, i.e., high‐speed plasma flows in this region, which is consistent with the result of Nakamura et al, although in some cases conductances can be significant also outside the electron arcs [ Amm et al , 1999].…”

Section: Discussionsupporting

confidence: 85%

“…In our case the R1 current system persisted still during the duskward flow diversion. The EC pattern drifted as a stable configuration westward similarly as in the case of a substorm time streamer analyzed by Amm et al [1999]. Around the time when the H β band was brightest and at its most poleward position (1958 UT) the region of upward FAC already left the MIRACLE field of view.…”

Section: Discussionmentioning

confidence: 62%

“…In meridional scanning photometer data streamers appear first as poleward boundary intensifications which later drift equatorward [ Lyons et al , 1999; Zesta et al , 2000]. Observational evidence for the wedge‐like R1‐type current system is presented in the studies by Amm et al [1999] and Kauristie et al [2000]. In the former paper the real three dimensional FAC current system related with an auroral streamer is deduced from ionospheric observations, while in the latter study, the connection between this type of current system (as monitored with equivalent current vectors) with bursty plasma sheet flows is established.…”

Section: Introductionmentioning

confidence: 99%

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Bursty bulk flow intrusion to the inner plasma sheet as inferred from auroral observations

et al. 2003

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[1] The physics of the interaction of bursty bulk flows (BBFs) with the near-Earth plasma is not yet known in detail. We address this issue with comprehensive observations made with the MIRACLE network during a well-documented streamer event. In this case an equatorward intruding auroral streamer inclined from northwest (NW) to southeast (SE) reached the region of the proton oval of 486 nm (H b ) luminosity. This H b band is assumed to map poleward of the !30 keV proton isotropic boundary, which is at geocentric distances $7-8 R E according to the appropriate magnetic field models. A significant enhancement (30%) in the H b luminosity was recorded just at the time and in the location where the equatorward end of the streamer reached the H b band. This enhancement implies a corresponding pressure enhancement in the equatorial magnetosphere. The simultaneous poleward shift of the H b emission suggests that also a magnetic field dipolarization took place in the same region. An NW-aligned electrojet (300-400 km in width) accompanied the equatorward development of the streamer (with streamer locating at the dusk flank of this electrojet), and it produced a sharp negative magnetic bay ($300 nT) resembling a substorm onset. Both auroral and equivalent current observations suggest that the plasma jet was not completely dissolved or stopped during this interaction, but rather diverted in the azimuthal direction. Equivalent currents reconstructed from ground magnetic field observations indicate that a R1-type field-aligned current system (upward current $0.5 MA) accompanied the streamer development. However, our observations do not show any signatures of a R2-type current system expected to build up during the flow braking and diversion according to previously published simulation studies.

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Section: Discussionsupporting

confidence: 93%

Section: Discussionsupporting

confidence: 85%

Section: Discussionmentioning

confidence: 62%

Section: Introductionmentioning

confidence: 99%

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Bursty bulk flow intrusion to the inner plasma sheet as inferred from auroral observations

et al. 2003

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“…Hereinafter, the transient flows we consider will be termed “rapid magnetospheric streams” rather than “bursty bulk flows” (BBFs), for we admit some difference between the two phenomena in spite of great similarity. Thus the authors who discovered the BBFs typically relate them to high auroral electrojet ( AE ) activity, impulsive magnetic reconnection as a basic mechanism, and substorm‐associated, north‐south‐aligned auroral structures as an ionospheric manifestation [ Baumjohann and Paschmann , 1990; Angelopoulos et al , 1992, 1993, 1994; Henderson et al , 1998; Lyons et al , 1999; Amm et al , 1999; Zesta et al , 2000]. We find the rapid magnetospheric streams to be most common under northward B z interplanetary magnetic field (IMF) and quiet geomagnetic conditions.…”

Section: Introductionmentioning

confidence: 89%

High‐latitude irregularities of the magnetospheric electric field and their relation to solar wind and geomagnetic conditions

2002

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[1] Having processed high-resolution electric field measurements of the low-altitude spacecraft Dynamic Explorer 2 in order to reveal and study signatures of rapid magnetospheric streams, we found that along with a regular large-scale electric field there exists an irregular one with amplitudes of 50-200 mV m À1 and transverse scale sizes varying from several to a hundred kilometers. This component behaves quite differently compared to the regular field: In particular, it is most common and of highest intensity under strong northward B z interplanetary magnetic field (IMF) and low AE and Dst conditions. Thus low average electric field (as expected and observed at quiet times) does not mean low variance. Large-amplitude electric field fluctuations typically occur at or around the convection reversal boundary, expanding to the central polar region or shifting to the equator depending on B z IMF direction. They are accompanied by large variations of the magnetic field component, with one-to-one correspondence of peaks and valleys of electric and magnetic field oscillations. The field-aligned currents inferred are on the order of 10 -100 A km À2 , which is large enough to be associated with discrete arcs.

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Coordinated SuperDARN THEMIS ASI observations of mesoscale flow bursts associated with auroral streamers

et al. 2014

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[1] Nightside auroral zone localized flow channels, typically associated with auroral poleward boundary intensifications and streamers, are an important component of high-latitude ionospheric plasma dynamics. We investigate the structure of these flow channels using two-dimensional line-of-sight flow observations from the Super Dual Auroral Radar Network (SuperDARN) radars and auroral images from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) ground-based all-sky imager (ASI) array. Radar echoes captured <~500 km horizontal distance from the radars were mainly used to detect small-scale flow structures that would otherwise be missed or poorly resolved in long-range radar echoes. After identifying 135 auroral streamers in the ASI images at close-radar capture locations, we examined the associated ionospheric flow data in the radar echoes. Flow bursts and streamers are invariably correlated in all events. The flow bursts are often directed equatorward and appear simultaneously with the streamers. Equatorward flows are located just to the east of the streamers. Less frequently (~10% of the time), a poleward flow enhancement was detected even when a streamer propagated equatorward, the poleward flow enhancement being located to the west of the auroral streamer, or to the east of the equatorward flow enhancement, consistently with the spatial relationship between flow shear and upward field-aligned currents in plasma sheet flow bursts. The azimuthal width of the flow channel is, on average,~75 km, and the azimuthal offset of the equatorward flow channel relative to the auroral streamer is~57 km eastward. This study demonstrates the capability of radar-imager pairs for identifying the 2-D structure of localized flows associated with plasma sheet flow bursts.

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Spatial distribution of conductances and currents associated with a north-south auroral form during a multiple-substorm period

Cited by 17 publications

References 29 publications

Bursty bulk flow intrusion to the inner plasma sheet as inferred from auroral observations

Bursty bulk flow intrusion to the inner plasma sheet as inferred from auroral observations

High‐latitude irregularities of the magnetospheric electric field and their relation to solar wind and geomagnetic conditions

Coordinated SuperDARN THEMIS ASI observations of mesoscale flow bursts associated with auroral streamers

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