Sudden impulses at low latitudes: Transient response

Russell, C. T.; Ginskey, M.

doi:10.1029/93gl01257

Cited by 18 publications

(18 citation statements)

References 10 publications

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“…Their amplitudes (increasing with latitude) overcome the asymptotic variations by a factor between ∼1.3 and ∼2.0, and are much greater (∼70 nT/nPa 1/2 at ∼53 • ; ∼28 nT/nPa 1/2 close to midnight at ∼29 • ) than those estimated by previous analysis (∼18 nT/nPa 1/2 at low latitudes; between ∼17.4 nT/nPa 1/2 and ∼22.5 nT/nPa 1/2 at ∼36 • ; 50-55 nT/nPa 1/2 at 54 • -58 • ; Russell and Ginskey, 1993;Russell and Ginskey, 1995). We determined the direction of the maximum overshoot fields and found them to be parallel to M1.…”

Section: An Analysis Of the Geomagnetic Responsecontrasting

confidence: 47%

“…On the other hand, overshoot amplitudes are much greater than in other cases. This aspect might be considered consistent with the significant reduction of the ring current in the period of interest (on 12 May, the D st index progressively increased from 2 to 37 nT between 10:00-18:00 UT, and attained values of 31 nT at 16:00 UT): Russell and Ginskey (1993), indeed, speculated that a stronger ring current would correspond to a higher damping of propagating compressional waves, with a consequent reduction of overshoot amplitudes.…”

Section: Discussionmentioning

confidence: 62%

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Some aspects of the geomagnetic response to solar wind pressure variations: a case study at low and middle latitudes

Villante¹,

Giuseppe²

2004

Ann. Geophys.

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Abstract. We examined geomagnetic field observations at low and middle latitudes in the Northern Hemisphere during a 50-min interval (12 May 1999), characterized by a complex behaviour of the solar wind dynamic pressure. For the entire interval, the aspects of the geomagnetic response can be organized into four groups of events which show common characteristics for the H and D components, respectively. The correspondence between the magnetospheric field and the ground components reveals different aspects of the geomagnetic response in different magnetic local time (MLT) sectors. For the H component, the correspondence is highly significant in the dusk and night sectors; in the dawn and prenoon sectors it shows a dramatic change across a separation line that extends approximately between (6 MLT, 35 • ) and (13 MLT, 60 • ). For the D component, the correspondence has significant values in the dawn and prenoon regions. We propose a new approach to the experimental data analysis which reveals that, at each station, the magnetospheric field has a close correspondence with the geomagnetic field projection along an axis (M1) that progressively rotates from north/south (night events) to east/west orientation (dawn events). When projected along M1, the geomagnetic signals can be interpreted in terms of a one-dimensional pattern that mostly reflects the field behaviour observed at geostationary orbit. Several features appear more evident in this perspective, and the global geomagnetic response to the SW pressure variations appears much clearer than in other representations. In particular, the MLT dependence of the geomagnetic response is much smaller than that one estimated by previous investigations. A clear latitudinal dependence emerges in the dusk sector. The occurrence of low frequency waves at ∼2.8 mHz can be interpreted in terms of global magnetospheric modes driven by the SW pulse. This event occurred in the recovery phase after the day the SW almost disappeared (11 May 1999): in this sense our results suggest a rapid recovery of almost typical magnetospheric conditionsCorrespondence to: U. Villante (umberto.villante@aquila.infn.it) soon after a huge expansion. Overshoot amplitudes, greater than in other cases, are consistent with a significant reduction of the ring current.

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Section: An Analysis Of the Geomagnetic Responsecontrasting

confidence: 47%

Section: Discussionmentioning

confidence: 62%

Some aspects of the geomagnetic response to solar wind pressure variations: a case study at low and middle latitudes

Villante¹,

Giuseppe²

2004

Ann. Geophys.

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“…Previous studies did not reveal the existence of this feature. In previous studies, the rapid response of the geomagnetic field at the shortest periods is a preliminary (positive or negative) impulse with a time scale of <1 min [ Araki , 1977, 1994; Russell and Ginskey , 1993, 1995; Kikuchi and Araki , 1985; Kikuchi et al , 2001]. The increase of the geomagnetic field over 30–40 min is certainly not the preliminary impulse.…”

Section: Summary and Discussionmentioning

confidence: 93%

“…The rapid response of the geomagnetic field at the shortest periods is a preliminary impulse with a time scale of <1 min [ Araki , 1977; Kikuchi and Araki , 1985]. The preliminary impulse is related to the field‐aligned current and interpreted as the arrival of the first Alfven wave along the magnetic field line at high latitudes caused by the distortion of the magnetosphere [ Le et al , 1993; Russell and Ginskey , 1993, 1995]. The preliminary impulse is further classified as a preliminary positive impulse for an increase of the geomagnetic field or a preliminary reverse impulse for a decrease of the geomagnetic field.…”

Section: Introductionmentioning

confidence: 99%

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Low‐latitude ionospheric electric and magnetic field disturbances in response to solar wind pressure enhancements

et al. 2008

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[1] We study the characteristics of the low-latitude ionospheric electric field and geomagnetic field in response to a sudden enhancement of the solar wind pressure. When the magnetosphere is compressed by an interplanetary shock, a significant enhancement in the dayside equatorial ionospheric ion vertical velocity occurs over 30-40 min and is measured by the Jicamarca incoherent scatter radar. A similar enhancement occurs in the high-latitude ionospheric convection and is detected by the SuperDRAN HF radars. The simultaneous enhancements of the ionospheric ion velocity at high and low latitudes provide strong evidence of the occurrence of penetration electric fields produced by solar wind pressure enhancements. The geomagnetic field first increases rapidly over 2-3 min and then falls over 30-40 min to an asymptotic value. The enhanced magnetic field occurs from the subauroral region to the equator at all local times. The time scale of 30-40 min is much longer than the conventional preliminary and main impulses of geomagnetic response to interplanetary shocks. There are two possible mechanisms that may be responsible for the generation of the enhanced ionospheric electric and magnetic fields. One mechanism is that the solar wind shock causes an over-compression of the magnetosphere, and the other is that the field-aligned and ionospheric currents driven by the solar wind shock cause the enhancements of the ionospheric electric and magnetic fields. However, neither of the mechanisms appears to be able to provide a complete explanation of all observed features.Citation: Huang, C.-S., K. Yumoto, S. Abe, and G. Sofko (2008), Low-latitude ionospheric electric and magnetic field disturbances in response to solar wind pressure enhancements,

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Inductive‐dynamic magnetosphere‐ionosphere coupling via MHD waves

Song

Vasyliūnas

2014

JGR Space Physics

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In the present study, we investigate magnetosphere-ionosphere/thermosphere (M-IT) coupling via MHD waves by numerically solving time-dependent continuity, momentum, and energy equations for ions and neutrals, together with Maxwell's equations (Ampère's and Faraday's laws) and with photochemistry included. This inductive-dynamic approach we use is fundamentally different from those in previous magnetosphere-ionosphere (M-I) coupling models: all MHD wave modes are retained, and energy and momentum exchange between waves and plasma are incorporated into the governing equations, allowing a self-consistent examination of dynamic M-I coupling. Simulations, using an implicit numerical scheme, of the 1-D ionosphere/thermosphere system responding to an imposed convection velocity at the top boundary are presented to show how magnetosphere and ionosphere are coupled through Alfvén waves during the transient stage when the IT system changes from one quasi steady state to another. Wave reflection from the low-altitude ionosphere plays an essential role, causing overshoots and oscillations of ionospheric perturbations, and the dynamical Hall effect is an inherent aspect of the M-I coupling. The simulations demonstrate that the ionosphere/thermosphere responds to magnetospheric driving forces as a damped oscillator.

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Sudden impulses at low latitudes: Transient response

Cited by 18 publications

References 10 publications

Some aspects of the geomagnetic response to solar wind pressure variations: a case study at low and middle latitudes

Some aspects of the geomagnetic response to solar wind pressure variations: a case study at low and middle latitudes

Low‐latitude ionospheric electric and magnetic field disturbances in response to solar wind pressure enhancements

Inductive‐dynamic magnetosphere‐ionosphere coupling via MHD waves

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