Variations of low‐latitude geomagnetic fields and <i>Dst</i> index caused by magnetospheric substorms

Huang, Chao-Tsung; Foster, J. C.; Гончаренко, Л. П.; Reeves, G. D.; Chau, Jorge L.; Yumoto, K.; Kitamura, Kentarou

doi:10.1029/2003ja010334

Cited by 58 publications

(68 citation statements)

References 47 publications

(90 reference statements)

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“…This effect has been confirmed by the Rice Convection Model (RCM) with a time-dependent magnetic field model [Sazykin, 2000;De Zeeuw et al, 2004;Maruyama et al, 2007;Zhang et al, 2009] and has been discussed with observations [Wei et al, 2008b[Wei et al, , 2009. On the other hand, the IMF northward turning is preferable to trigger substorms [Lyons et al, 1997], but the effect of substorm on overshielding, reduction [e.g., Huang et al, 2004;Huang, 2009] or enhancement [Wei et al, 2009;Zhang et al, 2009] is still a controversial issue.…”

Section: Introductionmentioning

confidence: 84%

“…On one hand, substorms can enhance plasma convection [e.g., Miyashita et al, 2008] and thus enhance the duskward penetration electric field [Huang et al, 2004;Huang, 2009]. Some simulations show that the enhancement of auroral conductance enables further penetration of convection electric field to lower latitude and reduces the shielding electric field that is fed by the region 2 FACs, though the enhanced auroral conductance results in a relatively stronger ring current and stronger region 2 FACs [Zheng et al, 2008].…”

Section: The Shape Of Imf Northward Turningmentioning

confidence: 99%

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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: 84%

Section: The Shape Of Imf Northward Turningmentioning

confidence: 99%

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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“…When the magnetosphere is compressed by an enhancement of the solar wind pressure, the dayside magnetopause current is intensified, resulting in an increase of the low-latitude geomagnetic field. IMF reorientations influence the low-latitude geomagnetic field through an electric field penetration process [Nishida, 1968;Fejer et al, 1979;Kelley et al, 1979Kelley et al, , 2003Kikuchi and Araki, 1979;Huang and Foster, 2001;Huang et al, 2002Huang et al, , 2004Huang et al, , 2005Huang et al, , 2006. When the IMF turns from northward to southward, the interplanetary electric field can penetrate into the equatorial ionosphere and cause an eastward electric field in the dayside ionosphere, resulting in disturbances in the ionospheric currents and magnetic field.…”

Section: Introductionmentioning

confidence: 99%

“…Magnetospheric substorms also generate geomagnetic disturbances at middle and low latitudes [Kikuchi et al, 2000[Kikuchi et al, , 2003Sastri et al, 2001]. As discussed by Huang et al [2004], tail current disruption, magnetotail dipolarization, and electric field penetration processes associated with substorms can cause geomagnetic disturbances on both the dayside and nightside.…”

Section: Introductionmentioning

confidence: 99%

Quantification and hemispheric asymmetry of low‐latitude geomagnetic disturbances caused by solar wind pressure enhancements

Huang¹,

Yumoto²

2006

J. Geophys. Res.

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[1] The solar wind dynamic pressure has significant influence on the magnetic field of the Earth. When the magnetosphere is compressed by a solar wind pressure enhancement, the dayside magnetopause current is enhanced, resulting in an increase in the magnetic field inside the magnetosphere and on the ground. In this paper we present the statistical results of low-latitude geomagnetic disturbances caused by solar wind pressure enhancements under different interplanetary magnetic field (IMF) orientations, including northward, southward, and fluctuating IMF. One of the prominent features of the geomagnetic disturbances revealed in this study is the hemispheric asymmetry and its seasonal dependence. Geomagnetic disturbances in the Northern Hemisphere summer are in general larger than those found simultaneously in the Southern Hemisphere and are smaller in the Northern Hemisphere winter than in the corresponding southern stations. The ratio of the average geomagnetic disturbance at magnetic latitude 36°S to that at magnetic latitude 36°N in winter is 1.36 for northward IMF, 1.64 for fluctuating IMF, and 1.79 for southward IMF. The corresponding ratio at 24°magnetic latitude is 1.49, 1.64, and 2.0, respectively. We suggest that the hemispheric asymmetry is caused by the tilt of the Earth's magnetic axis. Our statistics includes a large data set (160 cases in total), and we derive an empirical formula between the solar wind pressure enhancement and geomagnetic disturbances:, where DH is the change of the low-latitude geomagnetic field and measured with nT, P sw is the solar wind pressure and measured with nPa, and k is a constant. The value of k depends on seasons and is 18.4 if all data are included.Citation: Huang, C.-S., and K. Yumoto (2006), Quantification and hemispheric asymmetry of low-latitude geomagnetic disturbances caused by solar wind pressure enhancements,

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“…Prompt penetration electric fields have been suggested to lead to strong uplift of the F layer (Abdu et al, 2003;Huang et al, 2004) and are expected to occur on a global scale (Kelley, 1989). Substorms may likewise contribute significant short-term perturbations at equatorial latitudes.…”

Section: Electron Densities Tec and Gws In The F Layermentioning

confidence: 99%

The spread F Experiment (SpreadFEx): Program overview and first results

et al. 2009

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We performed an extensive experimental campaign (the spread F Experiment, or SpreadFEx) from September to November 2005 to attempt to define the role of neutral atmosphere dynamics, specifically wave motions propagating upward from the lower atmosphere, in seeding equatorial spread F and plasma bubbles extending to higher altitudes. Campaign measurements focused on the Brazilian sector and included ground-based optical, radar, digisonde, and GPS measurements at a number of fixed and temporary sites. Related data on convection and plasma bubble structures were also collected by GOES 12 and the GUVI instrument aboard the TIMED satellite. Initial results of our analyses of SpreadFEx and related data indicate 1) extensive gravity wave (GW) activity apparently linked to deep convection predominantly to the west of our measurement sites, 2) the presence of small-scale GW activity confined to lower altitudes, 3) larger-scale GW activity apparently penetrating to much higher altitudes suggested by electron density and TEC fluctuations in the E and F regions, 4) substantial GW amplitudes implied by digisonde electron densities, and 5) apparent direct links of these perturbations in the lower F region to spread F and plasma bubbles extending to much higher altitudes. Related efforts with correlative data are defining 6) the occurrence and locations of deep convection, 7) the spatial and temporal evolutions of plasma bubbles, the 8) 2D (height-resolved) structures of plasma bubbles, and 9) the expected propagation of GWs and tides from the lower atmosphere into the thermosphere and ionosphere.

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Variations of low‐latitude geomagnetic fields and Dst index caused by magnetospheric substorms

Cited by 58 publications

References 47 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

Quantification and hemispheric asymmetry of low‐latitude geomagnetic disturbances caused by solar wind pressure enhancements

The spread F Experiment (SpreadFEx): Program overview and first results

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