DC trains and Pc3s: Source effects in mid‐latitude geomagnetic transfer functions

Egbert, G. D.; Eisel, Markus; Boyd, O. S.; Morrison, H. F.

doi:10.1029/1999gl008369

Cited by 33 publications

(35 citation statements)

References 8 publications

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“…In other cases robust codes have been successful at reducing the effects of auroral sources, e.g., Garcia et al (1997). However, as noted by Egbert (1997) one cannot rely upon robust methods removing coherent noise, which essentially is what the nonuniform source field effects are, and Egbert et al (2000) demonstrate that robust processing yields estimates biased by non-uniform source fields in the 10-100 s period band.…”

Section: (Full Lines)mentioning

confidence: 99%

A simple method for deriving the uniform field MT responses in auroral zones

Jones

Spratt

2014

Earth Planet Sp

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Source field effects in magnetotelluric data acquired at high geomagnetic latitudes can result in erroneous interpretations of Earth conductivity structure deep within the mantle. This paper describes a simple technique most appropriate for a region that is dominantly one-dimensional (1-D) and uses the vertical magnetic field variations for identifying intervals of likely low contamination by non-uniform sources. Times are chosen when the variations stay within prescribed limits defined on the basis of a histogram of the variations for the whole recording interval. An example is given showing application of the method for data from a site under the auroral oval at a time when solar activity was at its lowest for the last solar cycle. A model derived from the responses obtained by processing all available data implies a decrease in resistivity at about 350 km to about 100 .m. In contrast, the model obtained from low activity interval responses shows a less rapid decrease in resistivity, without a change at around the 410 km phase boundary. The responses obtained from all data can be explained by the influence of a source with an average wavelength of 3,000 km.

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Section: (Full Lines)mentioning

confidence: 99%

A simple method for deriving the uniform field MT responses in auroral zones

Jones

Spratt

2014

Earth Planet Sp

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“…They can also produce ULF fields looking like pulsations (e.g. Jones and Kelly, 1966;FraserSmith, 1981;Egbert et al, 2000), and indirectly add noise to other measurements (e.g. at the CERN LEP accelerator, Bravin et al, 1998, and at a broad-band vertical seismic sensor at Stuttgart, Forbriger, 2007).…”

Section: Introductionmentioning

confidence: 99%

DC railways and the magnetic fields they produce—the geomagnetic context

Lowes

2009

Earth Planet Sp

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DC electric railways produce magnetic fields, not only from the intended traction currents, but also from unintended earth-leakage currents; these fields, particularly those from the leakage currents, are becoming an increasing problem for geomagneticians. This paper introduces the relevant properties of DC-railway tractionpower circuits, and the various ways in which earth-leakage currents are produced, and discusses models of how these leakage currents vary along the track and with train position. It describes the geometry of the resultant magnetic fields, and gives the formal algebra for calculating the magnetic field when these leakage currents are known, but also suggests some simple approximations that could be used when the current distribution is not known in detail. This paper also summarises previous relevant papers.

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“…Particularly harmful in this respect are dc-electrified railways (Yanagihara, 1977;Tokumoto and Tsunomura, 1984;Lowes, 1987;Iliceto and Santarato, 1999;Egbert et al, 2000;Georgescu et al, 2002;Pádua et al, 2002). In principle, the current used for feeding trains flows in a closed circuit consisting of an overhead feeding line and the return path along the rails.…”

Section: Introductionmentioning

confidence: 99%

Modelling the disturbance caused by a dc-electrified railway to geomagnetic measurements

et al. 2007

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Magnetic fields created by a dc-electrified railway are a nuisance to the operation of a geomagnetic observatory and also disturb other electromagnetic studies. Theoretical formulas that enable quantitative estimates of the magnetic effect of a dc railway including leakage currents in the ground are presented in this paper. They are illustrated by numerical examples. The validity of the theoretical model was verified by measurements carried out in the vicinity of a nearly north-south railway in Calgary, Canada. The earth structure in that area is approximately layered, which is an assumption included in the theoretical model. The agreement between the measured magnetic fields due to trains and the theoretical values is good. Numerical computations indicate that magnetic fields larger than the maximum allowable noise level (assumed to be about 10 pT) at today's magnetic observatories may extend to distances of tens of kilometres from a railway. We have prepared computer programs based on the theoretical formulas in the MatLab, Octave, FORTRAN and IDL languages, in which the locations (i.e. the latitudes and the longitudes) of the point of observation, of the feeding substations and of the trains, together with the feeding and leakage currents and the heights of the feeding lines, can be given as inputs.

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DC trains and Pc3s: Source effects in mid‐latitude geomagnetic transfer functions

Cited by 33 publications

References 8 publications

A simple method for deriving the uniform field MT responses in auroral zones

A simple method for deriving the uniform field MT responses in auroral zones

DC railways and the magnetic fields they produce—the geomagnetic context

Modelling the disturbance caused by a dc-electrified railway to geomagnetic measurements

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