Comparison of UV optical signatures with the substorm current wedge as predicted by an inversion algorithm

Сергеев, В. А.; Vagina, L. I.; Elphinstone, R. D.; Murphree, J. S.; Hearn, D. J.; Cogger, L. L.; Johnson, Michael L.

doi:10.1029/95ja00537

Cited by 39 publications

(43 citation statements)

References 19 publications

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“…Using mid-latitude ground observations (25 INTERMAG-NET stations with magnetic latitudes between 15 • and 55 • ) we calculated the locations and intensity of the substorm current wedge (SCW) (see Sergeev et al, 1996a, for a description of the algorithm). It started to develop at ∼02:27 UT, was centered at about 23:00 MLT, and had a longitudinal width of ∼3 h in MLT (i.e.…”

Section: Substorm Current Wedge Dynamicsmentioning

confidence: 99%

Multi-spacecraft observation of plasma dipolarization/injection in the inner magnetosphere

et al. 2007

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Abstract. Addressing the origin of the energetic particle injections into the inner magnetosphere, we investigate the 23 February 2004 substorm using a favorable constellation of four Cluster (near perigee), LANL and Geotail spacecraft. Both an energy-dispersed and a dispersionless injection were observed by Cluster crossing the plasma sheet horn, which mapped to 9-12 R E in the equatorial plane close to the midnight meridian. Two associated narrow equatorward auroral tongues/streamers propagating from the oval poleward boundary could be discerned in the global images obtained by IMAGE/WIC. As compared to the energy-dispersed event, the dispersionless injection front has important distinctions consequently repeated at 4 spacecraft: a simultaneous increase in electron fluxes at energies ∼1..300 keV, ∼25 nT increase in B Z and a local increase by a factor 1.5-1.7 in plasma pressure. The injected plasma was primarily of solar wind origin. We evaluated the change in the injected flux tube configuration during the dipolarization by fitting flux increases observed by the PEACE and RAPID instruments, assuming adiabatic heating and the Liouville theorem. Mapping the locations of the injection front detected by the four spacecraft to the equatorial plane, we estimated the injection front thickness to be ∼1 R E and the earthward propagation speed to be ∼200-400 km/s (at 9-12 R E ). Based on observed injection properties, we suggest that it is the underpopulated flux tubes (bubbles with Correspondence to: S. V. Apatenkov (apatenkov@geo.phys.spbu.ru) enhanced magnetic field and sharp inner front propagating earthward), which accelerate and transport particles into the strong-field dipolar region.

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Section: Substorm Current Wedge Dynamicsmentioning

confidence: 99%

Multi-spacecraft observation of plasma dipolarization/injection in the inner magnetosphere

et al. 2007

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“…The longitudinal locations of upward and downward FACs, as well as their magnitude as a function of time were modeled to fit the midlatitude magnetic field variations [Horning et al, 1974;Sergeev et al, 1996]. The current wedge started to develop at approximately 0525 UT with the upward and downward currents located at $20.5 MLT and $23 MLT, respectively.…”

Section: Introductionmentioning

confidence: 99%

Substorm current wedge driven by plasma flow vortices: THEMIS observations

et al. 2009

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[1] A multipoint analysis of conjugate magnetospheric and ionospheric flow vortices during the formation of the substorm current wedge (SCW) on 19 February 2008 is presented. During the substorm, four Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft were located close to the neutral sheet in the premidnight region between 9 and 12 R E geocentric distance, of which three closely ($1-2 R E ) clustered at $23 MLT and one was farther west at $21 MLT. The closely clustered spacecraft were engulfed by a counterclockwise plasma flow vortex, while the single spacecraft recorded a clockwise plasma flow vortex. Simultaneously, a pair of conjugate flow vortices with clockwise and counterclockwise rotation appeared in the ionosphere, as inferred from equivalent ionospheric currents. The counterclockwise space vortex, which corresponded to a downward field-aligned current, was at least 1-2 R E in diameter and had rotational flow speeds of up to 900 km/s. Current density estimates associated with the formation of the space vortex in the first 30 s yielded 2.8 nA/m 2 (14 mA/m 2 mapped to the ionosphere), or a total current of 1.1 Â 10 5 A. Model calculations based on midlatitude ground magnetometer data show a gradual increase of the field-aligned current, with 1-2 Â 10 5 A within the first minute and a peak value of 7 Â 10 5 A after 10 min, associated with the SCW, and a matching meridian of the downward current of the SCW and the downward current (counterclockwise) space vortex. The combined ground and space observations, together with the model results, present a scenario in which the space vortices generated the field-aligned current of the SCW at the beginning of the substorm expansion phase and coupled to the ionosphere, causing the ionospheric vortices.

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“…A magnetic data set put together by Ahn et al (1995) allowed them to study this event using the KRM method, with instantaneous conductivity based on Viking images. An inversion method determining magnetic local time (MLT) of currents (but not their strength) from midlatitude variations permitted Sergeev et al (1996) to study this event in conjunction with images from the Viking satellite. Another study (Lu et al 1997) is based primarily on AMIE and also presents GOES results, with an emphasis on mapping and no specific attention to the SCW total FAC.…”

Section: April 1 1986 Eventmentioning

confidence: 99%

Inverting magnetic meridian data using nonlinear optimization

Connors

Rostoker

2015

Earth Planet Sp

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A nonlinear optimization algorithm coupled with a model of auroral current systems allows derivation of physical parameters from data and is the basis of a new inversion technique. We refer to this technique as automated forward modeling (AFM), with the variant used here being automated meridian modeling (AMM). AFM is applicable on scales from regional to global, yielding simple and easily understood output, and using only magnetic data with no assumptions about electrodynamic parameters. We have found the most useful output parameters to be the total current and the boundaries of the auroral electrojet on a meridian densely populated with magnetometers, as derived by AMM. Here, we describe application of AFM nonlinear optimization to magnetic data and then describe the use of AMM to study substorms with magnetic data from ground meridian chains as input. AMM inversion results are compared to optical data, results from other inversion methods, and field-aligned current data from AMPERE. AMM yields physical parameters meaningful in describing local electrodynamics and is suitable for ongoing monitoring of activity. The relation of AMM model parameters to equivalent currents is discussed, and the two are found to compare well if the field-aligned currents are far from the inversion meridian.

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Comparison of UV optical signatures with the substorm current wedge as predicted by an inversion algorithm

Cited by 39 publications

References 19 publications

Multi-spacecraft observation of plasma dipolarization/injection in the inner magnetosphere

Multi-spacecraft observation of plasma dipolarization/injection in the inner magnetosphere

Substorm current wedge driven by plasma flow vortices: THEMIS observations

Inverting magnetic meridian data using nonlinear optimization

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