Electrodynamic coupling of high and low latitudes: Simulations of shielding/overshielding effects

Peymirat, C.; Richmond, A. D.; Kobea, A. T.

doi:10.1029/2000ja000057

Cited by 123 publications

(131 citation statements)

References 61 publications

(21 reference statements)

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“…The numerical simulations suggested that the duration of overshielding due to drop of the convection electric field is about 10-20 min, which is insufficient to explain the observed duration (typically 1-2 h) [Spiro et al, 1988]. With a time-independent magnetic field model, Peymirat et al [2000] also found that the simulated duration of overshielding is about half of the observed value. Fejer et al [1990] proposed that the magnetic field reconfiguration of the magnetosphere due to a northward turning and the associated shrinkage of the polar cap may effectively prolong the overshielding time period.…”

Section: Introductionmentioning

confidence: 92%

The transition to overshielding after sharp and gradual interplanetary magnetic field northward turning

Wei

Wan

et al. 2011

J. Geophys. Res.

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[1] Overshielding is referred to a shielding status, during which the dawnward shielding electric field dominates over the duskward penetration electric field in the inner magnetosphere, typically appearing when the interplanetary magnetic field (IMF) suddenly turns northward after a prolonged southward orientation. It is expected that the transition to overshielding after IMF northward turning can be affected by the shape of northward turning (sharp or gradual). Moreover, the initial shielding status (undershielding or goodshielding) prior to the transition may also have influence on the transition. Here we analyze two groups of cases, in which the transitions appear after sharp (duration less than 5 min) and gradual (duration more than 30 min) northward turning. Each group includes two cases, in which the transition initiated from undershielding and goodshielding. These cases show that (1) the beginning of the transition to overshielding coincides with sharp IMF northward turning but appears in the midst of gradual IMF northward turning; (2) the transition from goodshielding to overshielding is always associated with convection electric field drop and/or polar cap shrinkage, regardless of the shape of IMF northward turning; and (3) the typical solar wind condition in which the IMF suddenly turns northward after a prolonged southward orientation is neither a necessary condition nor a sufficient condition for overshielding. Furthermore, we will discuss the effect of substorm processes on overshielding.

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Section: Introductionmentioning

confidence: 92%

The transition to overshielding after sharp and gradual interplanetary magnetic field northward turning

Wei

Wan

et al. 2011

J. Geophys. Res.

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“…However, when the magnetospheric convection abruptly changes, the middle-and low-latitude ionosphere is temporarily exposed to the influence of high-latitude electric fields until the magnetospheric configuration readjusts and a new state of shielding is established. The time scale for the shielding processes is typically less than one hour (Kikuchi et al 2000;Peymirat et al 2000) but subject to magnetospheric conditions (Senior and Blanc 1984;. During the main phase of a geomagnetic storm, the penetration electric field is sometimes observed to last for several hours without decay (Kelley et al 2003;Huang et al 2005aHuang et al , 2005b.…”

Section: Storm Effectmentioning

confidence: 99%

Sq and EEJ—A Review on the Daily Variation of the Geomagnetic Field Caused by Ionospheric Dynamo Currents

2016

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A record of the geomagnetic field on the ground sometimes shows smooth daily variations on the order of a few tens of nano teslas. These daily variations, commonly known as Sq, are caused by electric currents of several μA/m 2 flowing on the sunlit side of the Eregion ionosphere at about 90-150 km heights. We review advances in our understanding of the geomagnetic daily variation and its source ionospheric currents during the past 75 years. Observations and existing theories are first outlined as background knowledge for the nonspecialist. Data analysis methods, such as spherical harmonic analysis, are then described in detail. Various aspects of the geomagnetic daily variation are discussed and interpreted using these results. Finally, remaining issues are highlighted to provide possible directions for future work.

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“…Many theoretical and experimental works during the last 3 decades dealt with the direct penetration of the polar cap electric field to equatorial latitudes [Wolf, 1970;Pellat and Laval, 1972;Senior and Blanc, 1984;Mazaudier et al, 1984;Spiro et al, 1988;Kobea et al, 2000;Peymirat et al, 2000].…”

Section: Ionospheric Disturbance Dynamomentioning

confidence: 99%

Magnetic signature of the ionospheric disturbance dynamo at equatorial latitudes: “D_dyn”

2005

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[1] During magnetic storms, wind disturbances produced by auroral phenomena can affect the whole thermospheric circulation and associated ionospheric dynamo currents for many hours after the end of the storms. In this paper we define criteria to select a new simple type of ionospheric disturbance dynamo events that allow a simple interpretation over all longitude sectors. These events exhibit a weak auroral activity during at least 24 UT hours, on the day after the storm. We analyze the magnetic disturbances ''D dyn '' observed at equatorial latitudes in the three longitude sectors of such selected events. It is found for all the cases that the amplitude of the H component of the Earth's magnetic field is reduced, on the day after storm at equatorial latitudes, in agreement with the ionospheric disturbance dynamo model (Blanc and Richmond, 1980). The observation of H component decrease on the day after storm is longitudinally asymmetric. The observed signature of the ionospheric disturbance dynamo process in a specific longitude sector is strongly dependent on the magnitude, the start time, and the duration of the storm.Citation: Le Huy, M., and C. Amory-Mazaudier (2005), Magnetic signature of the ionospheric disturbance dynamo at equatorial latitudes: ''D dyn '',

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Electrodynamic coupling of high and low latitudes: Simulations of shielding/overshielding effects

Abstract: Abstract.The penetration of the electric field and associated magnetic perturbations from high latitudes to low latitudes is studied with the Magnetosphere-Thermosphere- Ionosphere-Electrodynamics General

Cited by 123 publications

References 61 publications

The transition to overshielding after sharp and gradual interplanetary magnetic field northward turning

The transition to overshielding after sharp and gradual interplanetary magnetic field northward turning

Sq and EEJ—A Review on the Daily Variation of the Geomagnetic Field Caused by Ionospheric Dynamo Currents

Magnetic signature of the ionospheric disturbance dynamo at equatorial latitudes: “D_dyn”

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Electrodynamic coupling of high and low latitudes: Simulations of shielding/overshielding effects

Abstract: Abstract.The penetration of the electric field and associated magnetic perturbations from high latitudes to low latitudes is studied with the Magnetosphere-Thermosphere- Ionosphere-Electrodynamics General

Cited by 123 publications

References 61 publications

The transition to overshielding after sharp and gradual interplanetary magnetic field northward turning

The transition to overshielding after sharp and gradual interplanetary magnetic field northward turning

Sq and EEJ—A Review on the Daily Variation of the Geomagnetic Field Caused by Ionospheric Dynamo Currents

Magnetic signature of the ionospheric disturbance dynamo at equatorial latitudes: “Ddyn”

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Product

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Magnetic signature of the ionospheric disturbance dynamo at equatorial latitudes: “D_dyn”