The Influence of Continents and Oceans on Geomagnetic Variations

Parkinson, W. D.

doi:10.1111/j.1365-246x.1962.tb02992.x

Cited by 308 publications

(173 citation statements)

References 6 publications

Supporting

Mentioning

169

Contrasting

Unclassified

Order By: Relevance

“…The efficiency of the reflection increases with increasing conductivity so that, for a perfect horizontal conductor, the vertical field component Z in induced by the internal currents cancels the external field variations Z ext . The attenuation of the vertical component and, in addition, an increase of the horizontal component are predicted for a horizontal uniform conducting lamina which is representative of the Earth surface (Parkinson, 1962). The same result is predicted by Price (1950) when a spatially uniform external field induces currents in a half-space of uniform conductivity.…”

Section: Introductionsupporting

confidence: 60%

“…For example, at a land-sea interface, lateral conductivity gradients cause large Z values, inland from the border of the sea, as for example at observatories on the coastline, since the higher seawater conductivity provides a larger vertical field with respect to the land. In this case, the variation field still lies in a plane, the "Parkinson plane", which is no longer horizontal but is tilted upward toward the sea (Parkinson and Jones, 1979).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The geomagnetic coast effect at two 80° S stations in Antarctica, observed in the ULF range

et al. 2018

View full text Add to dashboard Cite

Abstract. We examined the coast effect in Antarctica along the 80 • S magnetic parallel. We used the geomagnetic field measurements at the two coastal stations of Mario Zucchelli Station and Scott Base, and, as a reference, at the inland temporary station Talos Dome, during 18 January-14 March 2008. Spectral analysis in the Pc5 frequency range (1-7 mHz) revealed large differences between coastal and inland stations, such as higher spectral power levels in the vertical component and higher coherence between horizontal and vertical components at coastal stations. Using the interstation method on selected active time intervals, with Talos Dome as a remote reference station, we found that remote reference induction arrows are directed almost perpendicularly with respect to their respective coastlines. Moreover, the singlestation analysis shows that at Talos Dome the amplitude of the induction arrows is much smaller than at coastal stations. These results clearly indicate that coast effect at a few hundred kilometers from the coastline is relatively small. The coast effect on polarization parameters was examined, for a Pc5 event that occurred on 11 March 2008. The results evidenced that the azimuthal angle of polarized signals at one of the coastal stations is largely different with respect to the inland station (by ∼ 110 • ), while the polarization ratio and ellipticity attain comparable values. We proposed a correction method of the polarization parameters, which operates directly in the frequency domain, obtaining comparable azimuthal angles at coastal and inland stations.

show abstract

Section: Introductionsupporting

confidence: 60%

Section: Introductionmentioning

confidence: 99%

The geomagnetic coast effect at two 80° S stations in Antarctica, observed in the ULF range

et al. 2018

View full text Add to dashboard Cite

show abstract

“…The induction arrows provide an insight into the conductivity distribution in the subsurface around the Serra da Cangalha impact crater region. They showed that the real part of the Parkinson (1962) induction ar-rows for 0.1 and 1.0 s point towards the center of the crater. This behavior indicates the presence of a radial conducting structure at this level in the subsurface.…”

Section: Validity Of the 3d Model Resultsmentioning

confidence: 99%

An integrated magnetotelluric and aeromagnetic investigation of the Serra da Cangalha impact crater, Brazil

Adepelumi

Fontes

Schnegg

et al. 2005

Physics of the Earth and Planetary Interiors

View full text Add to dashboard Cite

The research is aimed at delineating the post-impact structural characteristics across the Serra da Cangalha impact crater in Brazil using a combination of magnetotelluric (MT) and aeromagnetic data. The MT survey was carried out along three radial MT profiles trending NW-SE, ENE-WSW and NNE-SSW across the crater. For MT sites located further away from the centre of the crater, isotropic MT responses were observed, suggesting a 1D conductivity distribution in the subsurface in the frequency range of 100-10 Hz. For sites located in the vicinity of the inner ring of the crater, anisotropic responses were observed for the same frequency range. We believe that this zone probably represents the areas of structural disturbance. A 2D resistivity inversion of these data reveals a four-layer model, representing a thin resistive layer underlain by a conductive layer, a weathered basement and a resistive crystalline basement. The depth to the top of the basement is estimated to be about 1.2 km. This is in good agreement with the estimation of depth to the basement of about 1.1 km, calculated using the aeromagnetic data. However, in view of the circular geometry of the crater, we have carried out a 3D forward modeling computation to supplement the derived 2D model. The 3D resistivity forward model, fitting the MT responses by trial-by-error revealed a five-layer model, showing a significant reduction in the basement resistivity. This, perhaps, could be due to the structural disturbances that have been caused by the impact on the crater, resulting in brecciation, fracturing, alteration and shocked zone filled with weak-magnetic materials and fluids. We have calculated the effect of the impact on the overall structural deformation beneath the Serra da Cangalha crater, following the classical crater scaling relation of Holsapple and Schmidt [Holsapple, K.A., Schmidt, R.M., 1982

show abstract

“…Real tipper vectors in Parkinson 32 convention point towards the zone of high conductivity, whereas in Weise convention they point away from the zone of high conductivity. In the following we model tipper response recorded from the GHC.…”

Section: Three-dimensional Modelling Of Tipper Responsementioning

confidence: 99%

Transverse Tectonics Feature Delineated by Modelling of Magnetotelluric Data from Garhwal Himalaya Corridor, India

et al. 2016

View full text Add to dashboard Cite

We analyse magnetotelluric data recorded in the Garhwal Himalaya corridor, India, to study dimensionality and strike direction of the geoelectric structure. The geoelectric structure dimensionality in the corridor shows spatial variation with period. Geoelectric strike directions of the main Himalayan thrusts associated with the main arc -Main Frontal Thrust, Main Boundary Thrust and Main Central Thrust -are N72W  8, N70W  3 and N71W  6 respectively. Cross-strike directions oriented transverse and oblique with respect to the main arc geometry are also delineated. Transverse feature is constrained using 3D modelling.

show abstract

The Influence of Continents and Oceans on Geomagnetic Variations

Cited by 308 publications

References 6 publications

The geomagnetic coast effect at two 80° S stations in Antarctica, observed in the ULF range

The geomagnetic coast effect at two 80° S stations in Antarctica, observed in the ULF range

An integrated magnetotelluric and aeromagnetic investigation of the Serra da Cangalha impact crater, Brazil

Transverse Tectonics Feature Delineated by Modelling of Magnetotelluric Data from Garhwal Himalaya Corridor, India

Contact Info

Product

Resources

About