The Sq current system during the International Geophysical Year

Malin, S. R. C.; Gupta, Jagdish C.

doi:10.1111/j.1365-246x.1977.tb03720.x

Cited by 53 publications

(59 citation statements)

References 14 publications

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“…The difference between the values of the northern and southern foci indicates the total current intensity, which is about 300 kA, for the summer season. This is very high, when compared with the summer current intensities of other global regions (Malin and Gupta, 1977;Campbell and Schiffmacher, 1985). As observed in this study, Malin and Gupta (1977) also have reported a maximum intensity of current for Sq when its focus is located at mid-Pacific.…”

Section: Equivalent Ionospheric Source Current Systemssupporting

confidence: 63%

On the role of oceans in the geomagnetic induction by Sq along the 210° magnetic meridian region

2014

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We have utilized solar quiet daily variation (Sq) data recorded at a network of temporary and permanent magnetic observatories, operated along the western Pacific coast, in the 210• Magnetic Meridian (MM) region, spanning both hemispheres. The selected data sets correspond to solar-quiet year 1996. We have determined the ionospheric source current systems for all three Lloyd's seasons prior to calculating the Sq-induction response. As the selected data sets encompass the whole range of the western Pacific, we studied the role of self-induction effect (SIE) of the ocean at 24-hr period of Sq on the induction response, following the theory developed by Rikitake (1960). Our calculations show a considerable influence of the SIE on the induction response at 24-hr period, implying that ignoring the SIE in induction studies in oceanic regions leads to erroneous interpretation of the results. We have observed a large regional bias in the derived induction response estimates along the 210• MM region. As the ocean effect also depends on the regional subsurface structure and its conductivity, we believe that in addition to the SIE, the bias in the estimated response functions could be due to the strong influence of the coupling of the electric currents induced in the ocean and the highly heterogeneous upper mantle that has resulted from the active lithospheric convergence between the Pacific and Philippine Sea plates all along the western Pacific. We interpret the derived induction responses in the light of the tectonic significance of the 210• MM region. We also discuss the well-defined seasonal differences in ionospheric source current systems by comparing them with those reported for the East Asian sector.

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Section: Equivalent Ionospheric Source Current Systemssupporting

confidence: 63%

On the role of oceans in the geomagnetic induction by Sq along the 210° magnetic meridian region

2014

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“…In early studies of Sq, the mean (or median) value of the Sq variation was often used as the baseline. Later, however, it was realized that the average of nighttime values of the Sq variation is more physically meaningful because the source currents in the ionosphere effectively vanish during the night (e.g., Price and Wilkins 1963;Malin and Gupta 1977). At altitudes 100-150 km, nighttime Pedersen and Hall conductivities are a few orders of magnitude smaller than daytime values.…”

Section: Determination Of Baselinesmentioning

confidence: 99%

Sq and EEJ—A Review on the Daily Variation of the Geomagnetic Field Caused by Ionospheric Dynamo Currents

2016

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A record of the geomagnetic field on the ground sometimes shows smooth daily variations on the order of a few tens of nano teslas. These daily variations, commonly known as Sq, are caused by electric currents of several μA/m 2 flowing on the sunlit side of the Eregion ionosphere at about 90-150 km heights. We review advances in our understanding of the geomagnetic daily variation and its source ionospheric currents during the past 75 years. Observations and existing theories are first outlined as background knowledge for the nonspecialist. Data analysis methods, such as spherical harmonic analysis, are then described in detail. Various aspects of the geomagnetic daily variation are discussed and interpreted using these results. Finally, remaining issues are highlighted to provide possible directions for future work.

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“…Unfortunately, these advances on the theoretical front have not been matched by significant improvements in the quality or frequency range of the electromagnetic response data set. This is not to deny the value of those analyses which have been made, particularly of the periodic and quasi-periodic variations, such as the annual (MALIN and ISIKARA, 1976), eleven-year solar cycle (HARWOOD andMALIN, 1977, DucRuix et al, 1980) and daily variation (MALIN, 1977). Nonetheless, there seems to be a lack of confidence in the data as a whole, judging by the number of inversion attempts which restrict themselves to fitting relatively small subsets.…”

Section: Introductionmentioning

confidence: 99%

Strategies for improved global electromagnetic response estimates.

Banks

1981

J. geomagn. geoelec

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Efforts to make more precise and reliable measurements of the electromagnetic response of the Earth at periods less than a few days are baffled by the contamination of the magnetic variation data by currents which flow in the heterogeneous outer shell of the Earth. In this paper, quantitative estimates of the potential contamination are made by analysing induction in an Earth model which, in addition to the usual steep rise in conductivity at a depth of 500km, also involves a superficial conducting layer of integrated conductance 4,000S. It is concluded that (a) it may be possible, by careful selection of suitable stretches of data from observatories far from conductivity anomalies, to extend global electromagnetic response estimates to periods as short as 8 hours, but that (b) present response estimates in the period range 1-10 days may be contaminated by the currents in the outer shell.These hypotheses are tested by an investigation of the spatial and temporal variations in geomagnetic transfer functions observed at stations in Europe during a three-month period. Two events recorded during that time show distinctly different responses in the period range 1-3 days. The first yields temporally and spatially consistent values of the transfer function linking vertical and horizontal north components. The excitation is most probably of ring current origin, and the bulk of the induced current flows in the deep, spherically symmetric part of the Earth. The transfer functions generated by the second event are also consistent with time, but differ substantially from one obervatory to another. The source of this event is a current system which is spatially non-uniform. The transfer function is partly determined by the configuration of the localised external current system, and partly by the geometry of induced currents in the surface sheet. Both factors give rise to persistent relationships between the magnetic field components, which contaminate the global response estimates.

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The Sq current system during the International Geophysical Year

Cited by 53 publications

References 14 publications

On the role of oceans in the geomagnetic induction by Sq along the 210° magnetic meridian region

On the role of oceans in the geomagnetic induction by Sq along the 210° magnetic meridian region

Sq and EEJ—A Review on the Daily Variation of the Geomagnetic Field Caused by Ionospheric Dynamo Currents

Strategies for improved global electromagnetic response estimates.

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