The relationship between field-aligned currents and the auroral electrojets: A review

Kamide, Y.

doi:10.1007/bf00215281

Cited by 75 publications

(48 citation statements)

References 346 publications

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“…It is also shown that the different aspects of substorms reflect the different situations where the fast reconnection is triggered (Ugai, 2009b). Recently, it is demonstrated that impulsive magnetic pulsations like the Pi2 pulsations, observed at substorm onsets (Kamide, 1982), can be generated near the loop footpoint (Ugai, 2009c). Hence, it may be said that the spontaneous fast reconnection model is, in principle, responsible for the basic physical mechanism of complicated substorm phenomena.…”

Section: Summary and Discussionmentioning

confidence: 99%

Magnetic field structure of large-scale plasmoid generated by the fast reconnection mechanism in a sheared current sheet

Ugai

2010

Ann. Geophys.

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Abstract. On the basis of the spontaneous fast reconnection model, three-dimensional magnetic field profiles associated with a large-scale plasmoid propagating along the antiparallel magnetic fields are studied in the general sheared current sheet system. The plasmoid is generated ahead of the fast reconnection jet as a result of distinct compression of the magnetized plasma. Inside the plasmoid, the sheared (east-west) field component has the peak value at the plasmoid center located at x = X C , where the north-south field component changes its sign. The plasmoid center corresponds to the socalled contact discontinuity that bounds the reconnected field lines in x < X C and the field lines without reconnection in x > X C . Hence, contray to the conventional prediction, the reconnected sheared field lines in x < X C are not spiral or helical, since they cannot be topologically connected to the field lines in x > X C . It is demonstrated that the resulting profiles of magnetic field components inside the plasmoid are, in principle, consistent with satellite observations. In the ambient magnetic field region outside the plasmoid too, the magnetic field profiles are in good agreement with the well-known observations of traveling compression regions (TCRs).

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Section: Summary and Discussionmentioning

confidence: 99%

Magnetic field structure of large-scale plasmoid generated by the fast reconnection mechanism in a sheared current sheet

Ugai

2010

Ann. Geophys.

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“…The nature of the changes in the magnetospheric currents system during magnetospheric activity and the reasons for those changes have long been the subject of intense study [Alfvdn, 1981;Kamide, 1982;Stern, 1983]. Substorm studies have considered changes in the eastward and westward ionospheric electrojets, field-aligned currents (including region 1 and 2 currents), and the magnetospheric currents that connect them.…”

Section: Cuts Of the Mhd Currentmentioning

confidence: 99%

“…The interaction between the solar wind and the magnetosphere-ionosphere system produces several distinct electrical current systems including the Chapman-Ferraro or magnetopause currents, the cross-tail current system, and the substorm current system [Alfvdn, 1981;Kamide, 1982;Stern, 1983]. The substorm current system consists of ionospheric currents (eastward and westward electrojets), magnetospheric currents (the substorm current wedge and partial ring current), and FACs (including region 1 and 2 currents) that connect the magnetosphere and ionosphere.…”

Section: Introductionmentioning

confidence: 99%

Current disruption during November 24, 1996, substorm

El‐Alaoui¹

2001

J. Geophys. Res.

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Abstract. This study uses global magnetohydrodynamic (MHD) simulations driven by solar wind data along with Geotail, Interball, and IMP 8 observations of the magnetotail to investigate the dynamics of the near-Earth plasma sheet during a substorm that occurred on November 24, 1996. The MHD simulation shows that prior to the onset of the substorm, the magnitude of the current density decreases in a small region in the near-Earth plasma sheet. During and after the substorm onset this region of weak current becomes larger and more pronounced, expanding dawnward, duskward, upward, downward, and tailward. Part of the cross-tail current is redirected to the ionosphere via an earthward field-aligned current on the dawnside and a tailward return current on the duskside. The simulation showed that the field-aligned current was associated with velocity shear and flow vortices. IntroductionMagnetospheric substorms constitute one of the most intensively studied and controversial research areas in space physics. The general consensus is that the substorm process is initiated by a region of solar wind that has an interplanetary magnetic field (IMF) with a southward component. When this solar wind reaches the dayside magnetopause, dayside magnetic reconnection couples it to the magnetosphere and transfers energy to the magnetosphere. This energy is stored in the tail lobes in the form of a magnetic field and eventually triggers reconnection in the near-Earth magnetotail. While magnetotail reconnection is included in most substorm models, considerable controversy exists regarding just where in the magnetotail the reconnection occurs and how this location affects the onset of the expansion phase. Some investigators believe that the expansion phase starts as a disruption in the cross-magnetospheric current near the Earth, which later leads to reconnection farther down the tail [Lui et al., 1988, 1992]. (-34, 6, 16) to (-34.6, 4.3, 14.9) Re. The Interball spacecraft was also in the Northern Hemisphere and moved from (-18.8, 1.6, 12.7) to (-20.8, 1.6, 12.3) Re. Notice that Interball moved away from the Earth mainly in the x-direction, while IMP 8 moved toward the plasma sheet in the y-z plane. The Geotail spacecraft, on the other hand, was closer to the equatorial plane and moved from (-20.4, 3.16, -2.26) to (-22, 0.9, -2.53

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“…The importance of FACs for our understanding of ionospheremagnetosphere-solar wind coupling and interaction has naturally led to a vast number of studies and a number of review papers (e.g. Anderson and Vondrak, 1975;Kamide, 1982;Christiansen et al, 2002;Juusola et al, 2009). Zmuda et al (1966Zmuda et al ( , 1967 published the first direct evidence of their existence and later the average configuration of the field-aligned currents was determined (Zmuda and Armstrong, 1974;Rostoker et al, 1975;Iijima and Potemra, 1978).…”

Section: Introductionmentioning

confidence: 99%

Characteristics of the terrestrial field-aligned current system

et al. 2011

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Abstract. We present the first ever comprehensive statistical study of the spatiotemporal characteristics of field-aligned currents in the terrestrial magnetosphere-ionosphere system using multi point measurements. We determine how the FAC density, variability and scale size are coupled. The three ST 5 satellites were in a pearls-on-a-string formation making measurements of the magnetic field with variable interspacecraft separations ranging from a few seconds to about 10 min. More than 4700 sets of satellite passes are analyzed using a robust correlation analysis aimed at determining the variability of the FAC system as a function of scale size and satellite spacing. We find significant differences between the FAC characteristics on the dayside and on the nightside in terms of dynamics of the current systems. On the dayside the FAC characteristics are found to be independent of IMF B z and geomagnetic activity while the nightside indicates increased variability during disturbed conditions. The boundary separating highly and poorly correlated FACs can be fitted by a linear line for satellite separations shorter than 60 s (dayside) and 160 s (nightside). We interpret this as the dayside and nightside magnetospheric reconfiguration times respectively. For times exceeding this the FAC characteristics are suggested to be controlled by the solar wind (dayside) and plasma sheet (nightside) dynamics. Finally, the characteristics of FAC system with scale sizes larger than ∼200 km (at ionospheric altitude) appear to be stable and repeatable on time scales of the order of a minute (i.e. comparable to the low-altitude orbiting satellite's traverse time across the auroral belt). In this sense, our results effectively validate the Iijima and Potemra (1978) assumption that on average the large-scale currents with scale sizes of the Region1 and Correspondence to: J. W. Gjerloev (jesper.gjerloev@ift.uib.no) Region2 are quasi-persistently significant in the transport of energy and momentum between the magnetosphere and the ionosphere.

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The relationship between field-aligned currents and the auroral electrojets: A review

Cited by 75 publications

References 346 publications

Magnetic field structure of large-scale plasmoid generated by the fast reconnection mechanism in a sheared current sheet

Magnetic field structure of large-scale plasmoid generated by the fast reconnection mechanism in a sheared current sheet

Current disruption during November 24, 1996, substorm

Characteristics of the terrestrial field-aligned current system

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