The state transition model of the substorm onset

Tanaka, Takashi

doi:10.1029/2000ja900061

Cited by 71 publications

(140 citation statements)

References 44 publications

(53 reference statements)

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“…However, dipolarization sets in earlier when the IMF is switched again northward. Since northward turning is expected to cause a reduction of the thinning rate in the plasma sheet, Tanaka (2000) concludes that the near-Earth neutral line is not the primary cause of dipolarization. Dipolarization may be due to enhanced transport of flux from a neutral line in the midtail, but can also be due to reduced transport to the dayside.…”

Section: Methodsmentioning

confidence: 99%

“…Solid curve for a north-south turning of the IMF; dashed curve for a north-south-north turning of the IMF (from Tanaka, 2000) conditions imposed at the inner shell are determined by requiring a static equilibrium, and field-aligned currents partly close in a smoothing region just above the inner shell. Tanaka (2000) has recently investigated the magnetospheric dynamics following a southward turning of the IMF by using the magnetosphere-ionosphere coupling model described above, where the field-aligned currents close in the ionosphere by Pedersen and Hall currents. Tanaka (2000) starts from a stationary solution with a northward IMF, which is inclined by 30° to the northward direction and then switches the IMF to an inclination of 150°.…”

Section: Methodsmentioning

confidence: 99%

“…Tanaka (2000) has recently investigated the magnetospheric dynamics following a southward turning of the IMF by using the magnetosphere-ionosphere coupling model described above, where the field-aligned currents close in the ionosphere by Pedersen and Hall currents. Tanaka (2000) starts from a stationary solution with a northward IMF, which is inclined by 30° to the northward direction and then switches the IMF to an inclination of 150°. In the growth phase southward turning of the IMF results in enhanced polar cap convection.…”

Section: Methodsmentioning

confidence: 99%

“…This resistivity is only switched on when it exceeds some critical value and is zero otherwise. A similar anomalous resistivity proportional to j 2 /|B| 2 was used by Tanaka (2000). However, no local threshold mechanism is introduced.…”

Section: Non-ideality In Mhd Simulationsmentioning

confidence: 99%

“…Fedder and Lyon (e.g., Fedder and Lyon, 1995) use a computer-generated distorted spherical coordinate system with its axis aligned with the solar wind flow. Tanaka (2000) uses a distorted grid with a dense allocation at the inner boundary (3 R E ) and in the plasma sheet…”

Section: Numerical Gridsmentioning

confidence: 99%

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Space Storms and Space Weather Hazards

Daglis¹

2001

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Subject Terms Report Classification unclassified Classification of this page unclassified Classification of Abstract unclassified Limitation of Abstract UU Number of Pages 486REPORT DOCUMENTATION PAGE Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget, -to review recent spacecraft measurements that have provided new insight into the dynamics and effects of space storms; -to review space weather hazards associated with space storms and pertinent to the operation of technological systems in space and on ground;-to discuss and assess methods of space weather forecasting, as well as national and international initiatives towards an efficient development of space climatology.Space weather, the invisible but nevertheless effective result of solar activity and solar-terrestrial coupling, has affected the operations of communication systems since the appearance of telegraph in the 19th century, though as an unknown trouble factor. Nowadays, the effects of space weather affect in various ways all communication modes, from cable to wireless to space-based systems. Moreover, space weather hazards include malfunction or even permanent damage of power distribution grids and of telecommunication, navigation and surveillance satellites, disturbances of over-the-horizon (OTH) radar, HF, VHF and UHF communications, surveying and navigation systems that use Global Positioning System (GPS) satellites, surveillance (optical and radar), and satellite tracking. Space weather influences on the Earth's weather and climate is still a developing topic. Little is known concerning the biological effects of space weather, especially regarding astronauts.This Institute could not be timelier. Space Weather, which has been defined as "conditions on the sun and in the solar wind, magnetosphere, ionosphere, and thermosphere that can influence the performance and reliability of space-and ground-based technological systems and can endanger human life", encompasses a broad range of phenomena impacting both space science and technology. The effects of Space Weather, while present throughout the solar cycle, gain particular prominence around the peak of the 11-year sunspot activity; the maximum of cycle 23 occurred in summer 2000.The fact that this ASI on Space Weather was held in Europe is particularly appropriate. European countries host a considerable repository of knowledge and world-class facilities in this field. Nevertheless, while Space Weather activities in c...

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Non-ideality In Mhd Simulationsmentioning

confidence: 99%

Section: Numerical Gridsmentioning

confidence: 99%

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Space Storms and Space Weather Hazards

Daglis¹

2001

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Global MHD modeling of ionospheric convection and field‐aligned currents associated with IMF B_y triggered theta auroras

et al. 2014

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Using numerical magnetohydrodynamic simulations, we investigate the evolution of ionospheric convection and field-aligned currents (FACs) when θ auroras are formed in response to interplanetary magnetic field (IMF) B y transitions. When the polarity of IMF B y switches abruptly during northward IMF periods, the crossbar of the θ aurora is isolated from the flankside auroral oval and drifts into the polar cap. This drift motion is involved in a large round cell associated with new IMF B y , with sunward convection residing only on the dayside tip of the crossbar. There exists an IMF B y -controlled large-scale FAC system on the crossbar. When the θ aurora is drifting duskward (dawnward), the FACs are located on the dawnside (duskside) boundary of the crossbar adjacent to the "new" lobe. In contrast, the magnetospheric source region of the crossbar FAC system is located on the duskside (dawnside) boundary of the protruded plasma sheet adjacent to the "old" lobe. In the source region, plasma thermal pressure feeds the electromagnetic energy of FACs, and these processes can be interpreted as coupling of slow mode and Alfvén mode disturbances. In the ionosphere, the crossbar-associated FACs close with part of the region 1 currents associated with the new crescent cell. The magnetospheric source of that part of the region 1 FACs is located on the plasma sheet boundary and the magnetopause both adjacent to the new lobe. Dynamo processes in the old-lobe side and the new-lobe side work together to drive the ionospheric drift motion of the crossbar.

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Counter equatorial electrojet and overshielding after substorm onset: Global MHD simulation study

2014

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By performing a global magnetohydrodynamic (MHD) simulation, we have demonstrated for the first time that an electrojet at the dayside magnetic equator can be reversed and an overshielding condition can be established in the inner magnetosphere after substorm onset without northward turning of the interplanetary magnetic field. Near the substorm onset, the plasma pressure is highly enhanced in the inner magnetosphere on the nightside. The Region 2 field-aligned current diverges from the diamagnetic current on the surface of the dayside extension of the high-pressure region, which is connected to the ionosphere in the relatively low-conductivity region a few degrees equatorward of the main auroral oval that is formed as the projection of the plasma sheet. The separation of the equatorward boundary of the auroral region and the equatorward boundary of the Region 2 current results in dusk-dawn electric fields that generate a counter electrojet (CEJ) at the dayside magnetic equator. Poleward electric fields in a narrow latitudinal width, which may be regarded as subauroral ion drift and subauroral polarization stream, are simultaneously intensified. The dusk-dawn electric fields may propagate to the inner magnetosphere along a field line as shear Alfvén waves. Then, the inner magnetosphere is completely constrained by the overshielding condition. The intensity and polarity of the CEJ depend largely on at least the ionospheric conductivity that is related to the plasma pressure (probably associated with diffuse aurora). This may explain the observational fact that overshielding does not always occur after onset.

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The state transition model of the substorm onset

Cited by 71 publications

References 44 publications

Space Storms and Space Weather Hazards

Space Storms and Space Weather Hazards

Global MHD modeling of ionospheric convection and field‐aligned currents associated with IMF B_y triggered theta auroras

Counter equatorial electrojet and overshielding after substorm onset: Global MHD simulation study

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The state transition model of the substorm onset

Cited by 71 publications

References 44 publications

Space Storms and Space Weather Hazards

Space Storms and Space Weather Hazards

Global MHD modeling of ionospheric convection and field‐aligned currents associated with IMF By triggered theta auroras

Counter equatorial electrojet and overshielding after substorm onset: Global MHD simulation study

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Global MHD modeling of ionospheric convection and field‐aligned currents associated with IMF B_y triggered theta auroras