The effect of fluctuating ionospheric electric fields on Es-occurrence at cusp and polar cap latitudes

Wan, Weixing; Liu, L.; Parkinson, M. L.; Liu, R.; He, Long; Breed, A. M.; Dyson, P. L.; Morris, R. J.

doi:10.1016/s0273-1177(01)00204-6

Cited by 5 publications

(4 citation statements)

References 13 publications

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“…3 also applies to other electric field strengths after the appropriate change in the time scale. The fact that a layer does not start forming at a convergent null has a further consequence: unlike that suggested by Wan et al (2001), the layer formation is probably not very sensitive to fluctuations in the electric field direction within the NW sector.…”

Section: Model Calculations Of Sporadic-e Generationmentioning

confidence: 82%

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IMF effect on sporadic-E layers at two northern polar cap sites: Part II – Electric field

Nygrén

Aikio²,

Voiculescu³

et al. 2006

Ann. Geophys.

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Abstract. This paper is the second in a series on a study of the link between IMF and sporadic-E layers within the polar cap. In Paper I (Voiculescu et al., 2006), an analysis of the sporadic-E data from Thule and Longyearbyen was presented. Here we concentrate on the electric field mechanism of sporadic-E generation. By means of model calculations we show that the mechanism is effective even at Thule, where the direction of the geomagnetic field departs from vertical only by 4 • . The model calculations also lead to a revision of the electric field theory. Previously, a thin layer was assumed to grow at a convergent null in the vertical ion velocity, which is formed when the electric field points in the NW sector. Our calculations indicate that in the dynamic process of vertical plasma compression, a layer is generated at altitudes of high vertical convergence rather than at a null. Consequently, the layer generation is less sensitive than previously assumed to fluctuations of the electric field direction within the NW sector. The observed diurnal variations of sporadic-E occurrence at Longyearbyen and Thule are compared with the diurnal variations of the electric field, calculated using a representative range of IMF values by means of the statistical APL model. The results indicate that the main features of Es occurrence can be explained by the convection pattern controlled by the IMF. Electric fields calculated from the IMF observations are also used for producing distributions of sporadic-E occurrence as a function of electric field direction at the two sites. A marked difference between the distributions at Thule and Longyearbyen is found. A model estimate of the occurrence probability as a function of electric field direction is developed and a reasonable agreement between the model and the experimental occurrence is found. The calculation explains the differences between the distributions at the two sites in terms of the polar cap convection pattern. The conclusion is that the electric field is the maCorrespondence to: T. Nygrén (tuomo.nygren@oulu.fi) jor cause for sporadic-E generation and, consequently, IMF has a clear control on the occurrence of sporadic E within the polar cap.

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Section: Model Calculations Of Sporadic-e Generationmentioning

confidence: 82%

“…This mechanism should only work at high latitudes, where electric fields of even tens of mV/m are commonly encountered. This theory seems to be widely accepted (Bristow and Watkins, 1991;Bedey and Watkins, 2001;Kirkwood and Nilsson, 2000;Parkinson et al, 1998Parkinson et al, , 2001Wan et al, 2001).…”

Section: Introductionmentioning

confidence: 96%

IMF effect on sporadic-E layers at two northern polar cap sites: Part II – Electric field

Nygrén

Aikio²,

Voiculescu³

et al. 2006

Ann. Geophys.

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“…During substorm expansion, electric fields are typically highly variable. If electric fields are fluctuating rapidly both in direction and intensity, there may not be enough time for the layer to form (Wan et al, 2001). However, this suggestion remains open to further investigations.…”

Section: Discussionmentioning

confidence: 99%

IMF effect on sporadic-E layers at two northern polar cap sites: Part I – Statistical study

et al. 2006

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Abstract. In this paper we investigate the relationship between polar cap sporadic-E layers and the direction of the interplanetary magnetic field (IMF) using a 2-year database from Longyearbyen (75.2 • CGM Lat, Svalbard) and Thule (85.4 • CGM Lat, Greenland). It is found that the MLT distributions of sporadic-E occurrence are different at the two stations, but both are related to the IMF orientation. This relationship, however, changes from the centre of the polar cap to its border. Layers are more frequent during positive B y at both stations. This effect is particularly strong in the central polar cap at Thule, where a weak effect associated with B z is also observed, with positive B z correlating with a higher occurrence of Es. Close to the polar cap boundary, at Longyearbyen, the B y effect is weaker than at Thule. On the other hand, B z plays there an equally important role as B y , with negative B z correlating with the Es occurrence. Since Es layers can be created by electric fields at high latitudes, a possible explanation for the observations is that the layers are produced by the polar cap electric field controlled by the IMF. Using electric field estimates calculated by means of the statistical APL convection model from IMF observations, we find that the diurnal distributions of sporadic-E occurrence can generally be explained in terms of the electric field mechanism. However, other factors must be considered to explain why more layers occur during positive than during negative B y and why the B z dependence of layer occurrence in the central polar cap is different from that at the polar cap boundary.

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“…Wan et al [26] investigated the polar Sporadic E (Es) related to the electric field in the ionosphere. They modeled the accumulation process of Fe + , by solving the continuity and static momentum equations with a simple atmospheric model.…”

Section: Polar Ionosphere At Zhongshan Stationmentioning

confidence: 99%

Progress in polar upper atmospheric physics research in China

Liu¹,

Yang²

2012

APS

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The Chinese Antarctic Great Wall, Zhongshan, Kunlun and Arctic Yellow River stations have unique geographical locations, well suited to carry out polar upper atmospheric observations. This paper reviews the tremendous history of nearly 30 years of Chinese polar expeditions and major progress in polar upper atmospheric physics research. This includes the polar upper atmospheric physics conjugate observation system at Zhongshan Station in the Antarctic and Yellow River Station in the Arctic, and original research achievements in polar ionospheric fields, aurora and particle precipitation, the polar current system, polar plasma convection, geomagnetic pulsations and space plasma waves, inter-hemispheric comparisons of the space environment, space weather in polar regions, power spectrum of the incoherent scatter radar, ionospheric heating experiments and polar mesospheric summer echoes, polar ionosphere-magnetosphere numerical simulation and others. Finally, prospects for Chinese polar upper atmospheric physics research are outlined.

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The effect of fluctuating ionospheric electric fields on Es-occurrence at cusp and polar cap latitudes

Cited by 5 publications

References 13 publications

IMF effect on sporadic-E layers at two northern polar cap sites: Part II – Electric field

IMF effect on sporadic-E layers at two northern polar cap sites: Part II – Electric field

IMF effect on sporadic-E layers at two northern polar cap sites: Part I – Statistical study

Progress in polar upper atmospheric physics research in China

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