Ring current space time inhomogeneities observed during intense geomagnetic storms

2009 ◽  
Vol 44 (2) ◽  
pp. 149-156
Author(s):  
V. Silbergleit ◽  
A. González
Keyword(s):  
Ring Current ◽  
Geomagnetic Storms ◽  
Space Time

scholarly journals Ring current space-time inhomogeneities in intense geomagnetic storms

2004 ◽  
Vol 43 (2) ◽  
pp. 205-215
Author(s):  
Alicia L. Clúa de Gonzalez ◽  
Aracy Mendes da Costa ◽  
Walter D. Gonzalez
Keyword(s):  
Ring Current ◽  
Geomagnetic Storms ◽  
Space Time

El desarrollo de la corriente de anillo parcial durante la fase inicial de una tempestad geomagnética causa una asimetría longitudinal en el campo magnético en la superficie terrestre, en bajas y medias latitudes. Con la finalidad de lograr un mejor entendimiento de las inhomogeneidades espaciales y temporales así producidas, se estudió el comportamiento de la componente horizontal (H) del campo magnético medido por magnetómetros de suelo, para las tempestades geomagnéticas intensas que ocurrieron los días 14-15 de mayo de 1997, 24-25 de septiembre y 18-19 de octubre de 1998, respectivamente, mediante la utilización de gráficos de tipo UT-LT. Los datos fueron tomados a cada minuto, para seis estaciones de baja a media latitud con una distribución longitudinal aproximadamente uniforme. Siguiendo los pasos usados para la preparación del índice simétrico introducido por Iyemori (Dst), se calcularon los perfiles locales de la componente H del campo geomagnético y se construyeron mapas de contorno, para cada una de las tempestades analizadas. Contornos con reducción del campo geomagnético, centrados en el atardecer, se asocian con la existencia de una corriente de anillo parcial, en tanto que contornos con un incremento del campo magnético observados en la proximidad de la media noche se interpretan como debidos a la corriente de expansión de subtempestades geomagnéticas. Los mapas de contorno UT-LT son también comparados con los índices geomagnéticos, parámetros del viento solar y campo magnético interplanetario.

scholarly journals Decay of the Dst field of geomagnetic disturbance after substorm onset and its implication to storm-substorm relation

1996 ◽  
Vol 14 (6) ◽  
pp. 608-618 ◽  
Author(s):  
T. Iyemori ◽  
D. R. K. Rao
Keyword(s):  
Ring Current ◽  
Geomagnetic Storms ◽  
Sharp Decrease ◽  
Geomagnetic Disturbance ◽  
Substorm Onset ◽  
Significant Development ◽  
H Index ◽  
Magnetospheric Tail ◽  
Storms And Substorms ◽  
Substorm Onsets

Abstract. In order to investigate the causal relationship between magnetic storms and substorms, variations of the mid-latitude geomagnetic indices, ASY (asymmetric part) and SYM (symmetric part), at substorm onsets are examined. Substorm onsets are defined by three different phenomena; (1) a rapid increase in the mid-latitude asymmetric-disturbance indices, ASY-D and ASY-H, with a shape of so-called `mid-latitude positive bay\\'; (2) a sharp decrease in the AL index; (3) an onset of Pi2 geomagnetic pulsation. The positive bays are selected using eye inspection and a pattern-matching technique. The 1-min-resolution SYM-H index, which is essentially the same as the hourly Dst index except in terms of the time resolution, does not show any statistically significant development after the onset of substorms; it tends to decay after the onset rather than to develop. It is suggested by a simple model calculation that the decay of the magnetospheric tail current after substorm onset is responsible for the decay of the Dst field. The relation between the IMF southward turning and the development of the Dst field is re-examined. The results support the idea that the geomagnetic storms and substorms are independent processes; that is, the ring-current development is not the result of the frequent occurrence of substorms, but that of enhanced convection caused by the large southward IMF. A substorm is the process of energy dissipation in the magnetosphere, and its contribution to the storm-time ring-current formation seems to be negligible. The decay of the Dst field after a substorm onset is explained by a magnetospheric energy theorem.

scholarly journals Role of the magnetospheric and ionospheric currents in the generation of the equatorial scintillations during geomagnetic storms

2004 ◽  
Vol 22 (9) ◽  
pp. 3195-3202 ◽  
Author(s):  
L. Z. Biktash
Keyword(s):  
Solar Wind ◽  
Electric Fields ◽  
Ring Current ◽  
Geomagnetic Storms ◽  
Equatorial Ionosphere ◽  
Experimental Investigations ◽  
Polar Regions ◽  
Ionospheric Currents ◽  
Geomagnetic Variations ◽  
Activity Effect

Abstract. The equatorial ionosphere parameters, Kp, Dst, AU and AL indices characterized contribution of different magnetospheric and ionospheric currents to the H-component of geomagnetic field are examined to test the geomagnetic activity effect on the generation of ionospheric irregularities producing VLF scintillations. According to the results of the current statistical studies, one can predict near 70% of scintillations from Aarons' criteria using the Dst index, which mainly depicts the magnetospheric ring current field. To amplify Aarons' criteria or to propose new criteria for predicting scintillation characteristics is the question. In the present phase of the experimental investigations of electron density irregularities in the ionosphere new ways are opened up because observations in the interaction between the solar wind - magnetosphere - ionosphere during magnetic storms have progressed greatly. According to present view, the intensity of the electric fields and currents at the polar regions, as well as the magnetospheric ring current intensity, are strongly dependent on the variations of the interplanetary magnetic field. The magnetospheric ring current cannot directly penetrate the equatorial ionosphere and because of this difficulties emerge in explaining its relation to scintillation activity. On the other hand, the equatorial scintillations can be observed in the absence of the magnetospheric ring current. It is shown that in addition to Aarons' criteria for the prediction of the ionospheric scintillations, models can be used to explain the relationship between the equatorial ionospheric parameters, h'F, foF2, and the equatorial geomagnetic variations with the polar ionosphere currents and the solar wind.

Energy spectra of the major ion species in the ring current during geomagnetic storms

1989 ◽  
Vol 94 (A4) ◽  
pp. 3579 ◽  
Author(s):  
L. M. Kistler ◽  
F. M. Ipavich ◽  
D. C. Hamilton ◽  
G. Gloeckler ◽  
B. Wilken ◽  
...  
Keyword(s):  
Ring Current ◽  
Geomagnetic Storms ◽  
Energy Spectra ◽  
Major Ion ◽  
Ion Species

Evolution of the ring current during two geomagnetic storms

1987 ◽  
Vol 92 (A7) ◽  
pp. 7459 ◽  
Author(s):  
A. T. Y. Lui ◽  
R. W. McEntire ◽  
S. M. Krimigis
Keyword(s):  
Ring Current ◽  
Geomagnetic Storms

scholarly journals Ring current influence on auroral electrojet predictions

1999 ◽  
Vol 17 (10) ◽  
pp. 1268-1275 ◽  
Author(s):  
H. Gleisner ◽  
H. Lundstedt
Keyword(s):  
Solar Wind ◽  
Ring Current ◽  
Geomagnetic Storms ◽  
Wind Data ◽  
Common Source ◽  
Neural Net ◽  
Operational Forecasting ◽  
Storms And Substorms ◽  
Highly Correlated ◽  
Strong Control

Abstract. Geomagnetic storms and substorms develop under strong control of the solar wind. This is demonstrated by the fact that the geomagnetic activity indices Dst and AE can be predicted from the solar wind alone. A consequence of the strong control by a common source is that substorm and storm indices tend to be highly correlated. However, a part of this correlation is likely to be an effect of internal magnetospheric processes, such as a ring-current modulation of the solar wind-AE relation. The present work extends previous studies of nonlinear AE predictions from the solar wind. It is examined whether the AE predictions are modulated by the Dst index.This is accomplished by comparing neural network predictions from Dst and the solar wind, with predictions from the solar wind alone. Two conclusions are reached: (1) with an optimal set of solar-wind data available, the AE predictions are not markedly improved by the Dst input, but (2) the AE predictions are improved by Dst if less than, or other than, the optimum solar-wind data are available to the net. It appears that the solar wind-AE relation described by an optimized neural net is not significantly modified by the magnetosphere's Dst state. When the solar wind alone is used to predict AE, the correlation between predicted and observed AE is 0.86, while the prediction residual is nearly uncorrelated to Dst. Further, the finding that Dst can partly compensate for missing information on the solar wind, is of potential importance in operational forecasting where gaps in the stream of real time solar-wind data are a common occurrence.Key words. Magnetospheric physics (solar wind · magnetosphere interactions; storms and substorms)

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