Variability of the ocean‐induced magnetic field predicted at sea surface and at satellite altitudes

Glazman, Roman E.; Golubev, Y. N.

doi:10.1029/2005jc002926

Cited by 8 publications

(12 citation statements)

References 27 publications

(68 reference statements)

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“…Because these three different studies involved two rather different numerical methods for calculation of the magnetic fields from the flow and three different parametrizations (say, different input ocean circulation models were used), there is now reasonable confidence about these results. Note, however, that Glazman and Golubev (2005) predict that the ocean circulation generated magnetic signals are much larger than the results of the above mentioned groups, reaching some tens of nT at sea level. Since no observations show such high magnetic signals due to ocean circulation, their prediction seems to be doubtful.…”

Section: Ocean Circulationmentioning

confidence: 80%

3-D Global Induction in the Oceans and Solid Earth: Recent Progress in Modeling Magnetic and Electric Fields from Sources of Magnetospheric, Ionospheric and Oceanic Origin

2008

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Electromagnetic induction in the Earth's interior is an important contributor to the near-Earth magnetic and electric fields. The oceans play a special role in this induction due to their relatively high conductivity which leads to large lateral variability in surface conductance. Electric currents that generate secondary fields are induced in the oceans by two different processes: (a) by time varying external magnetic fields, and (b) by the motion of the conducting ocean water through the Earth's main magnetic field. Significant progress in accurate and detailed predictions of the electric and magnetic fields induced by these sources has been achieved during the last few years, via realistic three-dimensional (3-D) conductivity models of the oceans, crust and mantle along with realistic source models. In this review a summary is given of the results of recent 3-D modeling studies in which estimates are obtained for the magnetic and electric signals at both the ground and satellite altitudes induced by a variety of natural current sources. 3-D induction effects due to magnetospheric currents (magnetic storms), ionospheric currents (Sq, polar and equatorial electrojets), ocean tides, global ocean circulation and tsunami are considered. These modeling studies demonstrate that the 3-D induction (ocean) effect and motionally-induced signals from the oceans contribute significantly (in the range from a few to tens nanotesla) to the near-Earth magnetic field. A 3-D numerical solution based on an integral equation approach is shown to predict these induction effects with the accuracy and spatial detail required to explain observations both on the ground and at satellite altitudes.

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Section: Ocean Circulationmentioning

confidence: 80%

3-D Global Induction in the Oceans and Solid Earth: Recent Progress in Modeling Magnetic and Electric Fields from Sources of Magnetospheric, Ionospheric and Oceanic Origin

2008

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“…For this analysis, level 2 data, which are corrected vector and scalar magnetic field magnitude with a 1 s time resolution in the Figure 1. The modeled ocean-generated magnetic field potential (units in nTm) at an altitude 430 km according to Glazman and Golubev [2005]. The largest potential magnitudes were observed in the Southern Ocean (within the Antarctic Circumpolar Current).…”

Section: Datamentioning

confidence: 99%

“…The modeled ocean‐generated magnetic field potential (units in nTm) at an altitude 430 km according to Glazman and Golubev [2005]. The largest potential magnitudes were observed in the Southern Ocean (within the Antarctic Circumpolar Current).…”

Section: Introductionmentioning

confidence: 99%

“…Measurements made in ocean eddies near Tasmania [Lilley et al, 1993] have shown that the magnitude of the OGMF may reach 25 nT, a value comparable with the magnitudes of magnetic fields from sources such as the magnetosphere and the ionosphere. At an altitude 430 km, the magnitude of the vertical component of the OGMF is estimated to be 1-3 nT [Glazman and Golubev, 2005]. The potential of the ocean generated magnetic field at this altitude is shown at Figure 1. [3] The number of studies that involve observational data is disproportionately smaller than the number of modeling studies.…”

Section: Introductionmentioning

confidence: 99%

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Ocean‐generated magnetic field study based on satellite geomagnetic measurements: 1. An error reduction technique for gridded data

Golubev¹

2011

J. Geophys. Res.

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[1] A data set of approximately 28 months of geomagnetic measurements, made by the CHAMP mission, is planned to study the ocean-generated magnetic field. An obstacle for using these data is the large statistical error associated with data averaging in each grid point of the regular grid. The error is 10 2 -10 3 times larger than the magnitude of the ocean-generated signal. Here, a technique designed to reduce this error that is based on a solution of the Laplace (Helmholtz) equation, is proposed. The main idea behind the technique is that the magnetic potential in free space obeys the Laplace equation while, in general, the statistical error does not. The approach allows a reduction of the error in the gridded data over several orders of magnitude and makes the data useable for studying the ocean-generated magnetic field. As a preliminary result for using the data for inferring the ocean-generated magnetic field, the density function is introduced and computed. The function's plot demonstrates the presence of major large-scale ocean current systems within the midlatitudes.Citation: Golubev, Y. (2011), Ocean-generated magnetic field study based on satellite geomagnetic measurements: 1. An error reduction technique for gridded data,

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“…The ocean‐generated magnetic field (the term introduced by Stephenson and Bryan [1992]) is a magnetic field that occurs as a result of the phenomenon of motional induction [e.g., Sanford , 1971; Chave , 1983; Chave and Luther , 1990; Larsen , 1992; Stephenson and Bryan , 1992; Lilley et al , 1993, 2001, 2004; Flosadóttir et al , 1997a, 1997b; Tyler et al , 2003; Vivier et al , 2004; Glazman and Golubev , 2005; Manoj et al , 2006]. A physical picture of the phenomenon is as follows.…”

Section: Introductionmentioning

confidence: 99%

Ocean‐generated magnetic field study based on satellite geomagnetic measurements: 2. Signal inference

Golubev¹

2012

J. Geophys. Res.

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[1] The work presented here is the second part of an ocean-generated magnetic field study and provides a procedure for inferring the ocean-generated magnetic field from satellite geomagnetic measurements. The procedure was first tested on synthetic data. The simulation employed a hypothetical satellite measuring the magnetic field at an altitude of 400 km. The "measurements" (generated by the CM4 and CHAOS models) included the core field, the lithospheric field, the ionospheric and magnetospheric fields, the secular variation, and the ocean-generated magnetic field. The search algorithm, as proposed in part 1, converts irregular measurements into fields on a regular grid. The filtration procedure is based on the Savitzky-Golay algorithm. The procedure includes four steps providing seven unknown filter parameters. Parameter values were obtained by solving the problem of minimizing the spatially averaged squared residuals between the inferred field and the model field. Then, the parameters were used in the filter to infer the ocean-generated magnetic field that was initially added to the "measurements." The inferred signal, although spatially corrupted and having a smaller magnitude (60% of the magnitude of the initial signal), indicated the presence of magnetic anomalies within the Southern Ocean. The technique was then applied to CHAMP geomagnetic measurements. The result of filtering was clear magnetic anomalies within the Southern Ocean with a spatial character that were close to what models of the ocean-generated magnetic field provided. The magnitude of the inferring signal was 5 nT, the corrected values were 7-8 nT, 1-2 nT larger than the modeled field magnitude. To compare the temporal variability of the inferred field with the variability of sea surface height, ten 10 by 10 areas were selected within the Southern Ocean and the root-mean-square of both SSH and the magnetic field were computed for each area. A comparison of the results indicated a close similarity between SSH and the magnetic field temporal variability, which allowed the identification of the inferred field as the ocean-generated magnetic field.Citation: Golubev, Y. (2012), Ocean-generated magnetic field study based on satellite geomagnetic measurements: 2. Signal inference,

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Variability of the ocean‐induced magnetic field predicted at sea surface and at satellite altitudes

Cited by 8 publications

References 27 publications

3-D Global Induction in the Oceans and Solid Earth: Recent Progress in Modeling Magnetic and Electric Fields from Sources of Magnetospheric, Ionospheric and Oceanic Origin

3-D Global Induction in the Oceans and Solid Earth: Recent Progress in Modeling Magnetic and Electric Fields from Sources of Magnetospheric, Ionospheric and Oceanic Origin

Ocean‐generated magnetic field study based on satellite geomagnetic measurements: 1. An error reduction technique for gridded data

Ocean‐generated magnetic field study based on satellite geomagnetic measurements: 2. Signal inference

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