Electric and Magnetic Fields at the Earth's Surface Due to Auroral Currents

Albertson, V. D.; Baelen, Johan A. Van

doi:10.1109/tpas.1970.292604

Cited by 71 publications

(36 citation statements)

References 5 publications

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“…Until recently, most of the GIC studies concentrated on considering effects of the simplest one-dimensional current system, an east-west aligned auroral electrojet (Albertson and Van Baelen (1970); Boteler et al (1997); Towle et al (1992)). However, a recent survey of dB/dt occurrence and their directional distribution (Viljanen, 1997;Viljanen et al, 2001) indicated that many large GIC events display a large contribution from the east-west dB/dt component, especially in the morning LT hours at auroral latitudes, which cannot be explained by AEJ effects.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the geometry of ionospheric current systems related to rapid geomagnetic variations

et al. 2004

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Abstract.To learn about the geometry and sources of the ionospheric current systems which generate strong geomagnetically induced currents, we categorize differential equivalent current systems (DEC) for events with strong dB/dt by decomposing them into the contributions of electrojet-type and vortex-type elementary systems. By solving the inverse problem we obtain amplitudes and locations of these elementary current systems. One-minute differences of the geomagnetic field values at the IMAGE magnetometer network in 1996-2000 are analysed to study the spatial distributions of large dB/dt events. The relative contributions of the two components are evaluated. In particular, we found that the majority of the strongest dB/dt events (100-1000 nT/min) appear to be produced by the vortex-type current structures and most of them occur in the morning LT hours, probably caused by the Ps6 pulsation events associated with auroral omega structures. For strong dB/dt events the solar wind parameters are shifted toward strong (tens nT) southward IMF, enhanced velocity and dynamic pressure, in order for the main phase of the magnetic storms to occur. Although these events appear mostly during magnetic storms when the auroral oval greatly expands, the area of large dB/dt stays in the middle part of the auroral zone; therefore, it is connected to the processes taking part in the middle of the magnetosphere rather than in its innermost region populated by the ring current.

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Section: Introductionmentioning

confidence: 99%

Evaluation of the geometry of ionospheric current systems related to rapid geomagnetic variations

et al. 2004

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“…This behaviour of Z s (x, ω) is in agreement with the statement about source effects in Section 2.2. Figure 5 shows that |Z s (x, ω)| varies much with x and that the statement given by Albertson and Van Baelen (1970) that the plane wave case would result in the largest electric field if the magnetic field is kept constant is not true. Anyway, it can be seen from Fig.…”

Section: Numerical Examplesmentioning

confidence: 95%

Ground effects of space weather investigated by the surface impedance

2009

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The objective of this paper is to provide a discussion of the surface impedance applicable in connection with studies of geomagnetically induced currents (GIC) in technological systems. This viewpoint means that the surface impedance is regarded as a tool to determine the horizontal (geo)electric field at the Earth's surface, which is the key quantity for GIC. Thus the approach is different from the traditional magnetotelluric viewpoint. The definition of the surface impedance usually involves wavenumber-frequency-domain fields, so inverse Fourier transforming the expression of the electric field in terms of the surface impedance and the geomagnetic field results in convolution integrals in the time and space domains. The frequency-dependent surface impedance has a high-pass filter character whereas the corresponding transfer function between the electric field and the time derivative of the magnetic field is of a low-pass filter type. The relative change of the latter transfer function with frequency is usually smaller than that of the surface impedance, which indicates that the geoelectric field is closer to the time derivative than to the magnetic field itself. An investigation of the surface impedance defined by the space-domain electric and magnetic components indicates that the largest electric fields are not always achieved by the plane wave assumption, which is sometimes regarded as an extreme case for GIC. It is also concluded in this paper that it is often possible to apply the plane wave relation locally between the surface electric and magnetic fields. The absolute value of the surface impedance decreases with an increasing wavenumber although the maximum may also be at a non-zero value of the wavenumber. The imaginary part of the surface impedance usually much exceeds the real part.

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“…It is a well-established fact that geomagnetic stomls influence electrical power transmission and distribution systems [1][2][3]. Previous cases of such storms in the northern latitudes have resulted in occasional power disruptions arid, in some cases, damage to transfbrmers [4].…”

Section: Objectivesmentioning

confidence: 99%

Impact of Quasi-DC Currents on Three-Phase Distribution Transformer Installations

McConnell¹,

Barnes²,

Tesche³

et al. 1992

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This report summarizes a series of tests designed to determine the response of quasi-dc currents on three-phase power distribution transformers for electric power systems, In general, if the dc injection is limited to the primary side of a step-down transformer, significar_t harmonic distortion is noted and an increase in the reactive power demand results. For dc injection on the secondary (load) side of the step-do,arn transformer, the harmonic content at the secondary side is quite high and saturation occurs with a relatively low level of dc injection; however, the reactive p(.,wer demand is significantly lower, These tests produced no apparent damage to the transforn',ers. Transfornmr damage is dependent on the duration of the dc excitation, the level of the excitation, and on the thermal characteristics of the transformer.

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Electric and Magnetic Fields at the Earth's Surface Due to Auroral Currents

Cited by 71 publications

References 5 publications

Evaluation of the geometry of ionospheric current systems related to rapid geomagnetic variations

Evaluation of the geometry of ionospheric current systems related to rapid geomagnetic variations

Ground effects of space weather investigated by the surface impedance

Impact of Quasi-DC Currents on Three-Phase Distribution Transformer Installations

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