Auroral electrojets during geomagnetic storms

Feldstein, Y. I.; Grafe, A.; Gromova, L. I.; Попов, В. А.

doi:10.1029/97ja00577

Cited by 44 publications

(47 citation statements)

References 13 publications

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“…The 6 February magnetic storm was moderate but the second one on 10 May was severe. For this storm the equatorward shifting of the centres of both electrojets (EE and WE) is in accord with earlier results (Feldstein et al, , 1997(Feldstein et al, , 1999.…”

Section: Latitudinal Cross Sections Of the Magnetic Disturbancesupporting

confidence: 81%

Auroral electrojets and boundaries of plasma domains in the magnetosphere during magnetically disturbed intervals

et al. 2006

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Abstract. We investigate variations in the location and intensity of the auroral electrojets during magnetic storms and substorms using a numerical method for estimating the equivalent ionospheric currents based on data from meridian chains of magnetic observatories. Special attention was paid to the complex structure of the electrojets and their interrelationship with diffuse and discrete particle precipitation and field-aligned currents in the dusk sector. During magnetospheric substorms the eastward electrojet (EE) location in the evening sector changes with local time from cusp latitudes ( ∼77 • ) during early afternoon to latitudes of diffuse auroral precipitation ( ∼65 • ) equatorward of the auroral oval before midnight. During the main phase of an intense magnetic storm the eastward currents in the noon-early evening sector adjoin to the cusp at ∼65 • and in the pre-midnight sector are located at subauroral latitude ∼57 • . The westward electrojet (WE) is located along the auroral oval from evening through night to the morning sector and adjoins to the polar electrojet (PE) located at cusp latitudes in the dayside sector. The integrated values of the eastward (westward) equivalent ionospheric current during the intense substorm are ∼0.5 MA (∼1.5 MA), whereas they are 0.7 MA (3.0 MA) during the storm main phase maximum. The latitudes of auroral particle precipitation in the dusk sector are identical with those of both electrojets. The EE in the evening sector is accompanied by particle precipitation mainly from the Alfvén layer but also from the near-Earth part of the central plasma sheet. In the lower-latitude part of the EE the field-aligned currents (FACs) flow into the ionosphere (Region 2 FAC), and at its higher-latitude part the FACs flow Correspondence to: A. Prigancova (geofpria@savba.sk) out of the ionosphere (Region 1 FAC). During intense disturbances, in addition to the Region 2 FAC and the Region 1 FAC, a Region 3 FAC with the downward current was identified. This FAC is accompanied by diffuse electron precipitation from the plasma sheet boundary layer. Actually, the triple system of FAC is observed in the evening sector and, as a consequence, the WE and the EE overlap. The WE in the evening sector comprises only the high-latitude periphery of the plasma precipitation region and corresponds to the Hall current between the Region 1 FAC and Region 3 FAC. During the September 1998 magnetic storm, two velocity bursts (∼2-4 km/s) in the magnetospheric convection were observed at the latitudes of particle precipitation from the central plasma sheet and at subauroral latitudes near the ionospheric trough. These kind of bursts are known as subauroral polarization streams (SAPS). In the evening sector the Alfvén layer equatorial boundary for precipitating ions is located more equatorward than that for electrons. This may favour northward electric field generation between these boundaries and may cause high speed westward ions drift visualized as SAPS. Meanwhile, high speed ion drifts cover a wider range...

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Section: Latitudinal Cross Sections Of the Magnetic Disturbancesupporting

confidence: 81%

Auroral electrojets and boundaries of plasma domains in the magnetosphere during magnetically disturbed intervals

et al. 2006

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“…13 a very close correlation between the most equatorward position of the eastward electrojet and the maximum value of SYM during the time of the positive bay is recognizable. This is in a good accordance with Feldstein et al (1998).…”

Section: Eastward Electrojetsupporting

confidence: 78%

“…Therefore, there is a tendency that the higher the ring current intensity, then the more equatorwards the electrojet moves. This fact agrees with Feldstein et al (1998). However, we should also consider the considerable scatter of points for small SYM values.…”

Section: Westward Electrojetsupporting

confidence: 65%

About the relationship between auroral electrojets and ring currents

Grafe

Feldstein

2000

Ann. Geophys.

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Abstract.The relationship between the storm-time ring current and the auroral electrojets is investigated using IMAGE magnetometer data, D St and H-SYM, and solar wind data. Statistical results as well as the investigation of single events show that the auroral electrojets occur also during nonstorm conditions without storm-time ring current development and even during the storm recovery phase of increasing D St . A close correlation between electrojet intensity and ring current intensity was not found. Though the eastward electrojet moves equatorward during the storm main phase there is no unequivocal relationship between the movement of the westward electrojet and the ring current development. All these results suggest that the auroral electrojets and the ring current develop more or less independently of each other.

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“…presence of eastward ionospheric currents at mid latitudes in the context of substorms was reported earlier by Feldstein et al (1997). From our model we envisage an ionospheric current configuration as sketched in Fig.…”

Section: An Improved Substorm Current Modelmentioning

confidence: 99%

Near-Earth magnetic signature of magnetospheric substorms and an improved substorm current model

Ritter

Lühr

2008

Ann. Geophys.

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Abstract. Based on a comprehensive catalogue with more than 4000 magnetospheric substorm entries from the years 2000-2005, the spatial distribution of the substorm-related magnetic signatures at mid and low latitudes around local midnight was investigated. Superposed epoch analysis of a larger number of recent observatory data from mid and low latitudes revealed a field strength increase that is consistent with the results of earlier studies. For the first time, the magnetic signature of the substorm current wedge formation is studied also in near-Earth satellite data from CHAMP. The average maximal deflection measured on board the satellite is smaller by a factor of 2 than that determined from ground observations. The recurrence frequency of substorms as well as the amplitude of their magnetic signature depends strongly on the prevailing magnetic activity. The observed average substorm-related magnetic field signatures cannot be described adequately by a simple current wedge model. A satisfactory agreement between model results and observations at satellite height and on ground can be achieved only if the current reconfiguration scenario combines four elements: (1) the gradual decrease of the tail lobe field, (2) the rerouting of a part of the cross-tail current through the ionosphere, (3) eastward ionospheric currents at low and mid latitudes driven by Region-2 field-aligned currents, and (4) a partial ring current connected to these Region-2 FACs.

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Auroral electrojets during geomagnetic storms

Cited by 44 publications

References 13 publications

Auroral electrojets and boundaries of plasma domains in the magnetosphere during magnetically disturbed intervals

Auroral electrojets and boundaries of plasma domains in the magnetosphere during magnetically disturbed intervals

About the relationship between auroral electrojets and ring currents

Near-Earth magnetic signature of magnetospheric substorms and an improved substorm current model

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