Estimation of the current density and analysis of the geometry of the current system surrounding the Earth

We report on the local structure of the Martian subsolar Magnetic Pileup Boundary (MPB) from minimum variance analysis of the magnetic field measured by the MAVEN spacecraft for six orbits. In particular, we detect a well defined current layer within the MPB&#8217;s fine structure and provide a local estimate of its current density and compare these results with the current density obtained by multi-fluid simulations. This current is of the order of hundreds of nAm-2 which results in a sunward Lorentz force of the order of 10-14&#160;Nm-3. We compare these results with multifluid numerical simulations. This force is associated with the gradient of the magnetic pressure, it accounts for the&#160;deflection of the solar wind ions near the MPB and for the acceleration of solar wind electrons which carry the interplanetary magnetic field through the MPB into the MPR. We also find that the thickness of the MPB current layer is of the order of both the upstream (magnetosheath) solar wind proton inertial length and convective gyroradius. The former is consistent&#160;with the demagnetization of the ions due to the Hall electric field, an effect observed&#160;recently at the Earth magnetopause, while the latter would imply kinetic processes are&#160;important at the MPB. This study supports recent results that report the presence of a steady current system around Mars in a similar way to the Earth.

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A DISCUSSION OF THE “FAULT” AND “DIKE” PROBLEMS IN MAGNETOTELLURIC THEORY

Geophysics ◽

10.1190/1.1439212 ◽

1963 ◽

Vol 28 (3) ◽

pp. 487-490 ◽

Cited By ~ 2

Author(s):

J. T. Weaver

Keyword(s):

Boundary Condition ◽

Electromagnetic Wave ◽

Current Density ◽

Normal Component ◽

The Earth ◽

Source Field ◽

Vertical Fault ◽

Explicit Mention

In two recent papers appearing in Geophysics, d’Erceville and Kunetz (1962) and Rankin (1962) have dealt with the magnetotelluric theory for a plane earth which contains a certain type of vertical fault. In both cases the results depend on a boundary condition which requires the assumption that the normal component of current density vanishes at the surface of the earth. While d’Erceville and Kunetz confine their attention to the region below the surface and thereby avoid explicit mention of the source field, Rankin follows Cagniard (1953) by considering a plane‐polarized electromagnetic wave normally incident on the surface of the earth. In this case, the assumed boundary condition is not correct, as we shall see later; indeed, it actually leads to a contradiction.

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Study of the applicability of the curlometer technique with the four Cluster spacecraft in regions close to Earth

Annales Geophysicae ◽

10.5194/angeo-30-597-2012 ◽

2012 ◽

Vol 30 (3) ◽

pp. 597-611 ◽

Cited By ~ 9

Author(s):

S. Grimald ◽

I. Dandouras ◽

P. Robert ◽

E. Lucek

Keyword(s):

Magnetic Field ◽

Current Density ◽

Ring Current ◽

Current System ◽

Sufficient Conditions ◽

Magnetic Activity ◽

Inner Magnetosphere ◽

Good Proxy ◽

The Magnetic Field ◽

Magnetospheric Current System

Abstract. Knowledge of the inner magnetospheric current system (intensity, boundaries, evolution) is one of the key elements for the understanding of the whole magnetospheric current system. In particular, the calculation of the current density and the study of the changes in the ring current is an active field of research as it is a good proxy for the magnetic activity. The curlometer technique allows the current density to be calculated from the magnetic field measured at four different positions inside a given current sheet using the Maxwell-Ampere's law. In 2009, the CLUSTER perigee pass was located at about 2 RE allowing a study of the ring current deep inside the inner magnetosphere, where the pressure gradient is expected to invert direction. In this paper, we use the curlometer in such an orbit. As the method has never been used so deep inside the inner magnetosphere, this study is a test of the curlometer in a part of the magnetosphere where the magnetic field is very high (about 4000 nT) and changes over small distances (ΔB = 1nT in 1000 km). To do so, the curlometer has been applied to calculate the current density from measured and modelled magnetic fields and for different sizes of the tetrahedron. The results show that the current density cannot be calculated using the curlometer technique at low altitude perigee passes, but that the method may be accurate in a [3 RE; 5 RE] or a [6 RE; 8.3 RE] L-shell range. It also demonstrates that the parameters used to estimate the accuracy of the method are necessary, but not sufficient conditions.

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The MLT distribution and detailed structure of ring current: MMS observations

10.5194/egusphere-egu21-3730 ◽

2021 ◽

Author(s):

Xin Tan ◽

Malcolm Dunlop ◽

Xiangcheng Dong ◽

Yanyan Yang ◽

Christopher Russell

Keyword(s):

Current Density ◽

Large Scale ◽

Ring Current ◽

Current System ◽

Radial Profile ◽

Three Dimensional ◽

Current Density Distribution ◽

Magnetic Storms ◽

In Situ Data

The ring current is an important part of the large-scale magnetosphere-ionosphere current system; mainly concentrated in the equatorial plane, between 2-7 RE, and strongly ordered between &#177; 30 &#176; latitude. The morphology of ring current directly affects the geomagnetic field at low to middle latitudes. Rapid changes in ring current densities can occur during magnetic storms/sub-storms. Traditionally, the Dst index is used to characterize the intensity of magnetic storms and to reflect the variation of ring current intensity, but this index does not reflect the MLT distribution of ring current. In fact, the ring current has significant variations with MLT, depending on geomagnetic activity, due to the influence of multiple factors; such as, the partial ring current, region 1/region 2 field-aligned currents, the magnetopause current and sub-storm cycle (magnetotail current). The form of the ring current has been inferred from the three-dimensional distribution of ion differential fluxes from neutral atom imaging; however, this technique can not directly obtain the current density distribution (as can be obtained using multi-spacecraft in situ data). Previous in situ estimates of current density have used: Cluster, THEMIS and other spacecraft groups to study the distribution of the ring current for limited ranges of either radial profile, or MLT and MLAT variations. Here, we report on an extension to these studies using FGM data from MMS obtained during the period September 1, 2015 to December 31, 2016, when the MMS orbit and configuration provided good coverage. We employ the curlometer method to calculate the current density, statistically, to analysis the MLT distribution according to different geomagnetic conditions. Our results show the clear asymmetry of the ring current and its different characteristics under different geomagnetic conditions.

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Saturn’s ring current observed during Cassini’s Grand Finale

10.5194/egusphere-egu2020-11306 ◽

2020 ◽

Author(s):

Gabrielle Provan ◽

Tom Bradley ◽

Emma Bunce ◽

Stan Cowley ◽

Michele Dougherty ◽

...

Keyword(s):

Solar Wind ◽

Current Density ◽

Ring Current ◽

Current System ◽

Current Model ◽

Internal Field ◽

Total Current ◽

Magnetometer Data ◽

Proton Data ◽

Azimuthal Current

The presence of a substantial azimuthal current sheet in Saturn&#8217;s magnetosphere was identified in Voyager and Pioneer magnetometer data. &#160;Data from these spacecraft showed depressions in the strength of the field below that expected for the internal field of the planet alone. &#160;This ring current was&#160; modelled &#160;as a simple axisymmetric current system by Connerney et al. [1980, 1983]. &#160;In this study we utilise the Connerney ring current model to look at the size, shape, current density and total current of Saturn&#8217;s ring current as observed during the Cassini proximal orbits. &#160;We compare the variations in these parameters with the phases of the planetary period oscillations and with the occurrence of magnetospheric storms as determined from propagated solar wind data and LEMMS electron and proton data. Overall, we find that Saturn&#8217;s ring current is a dynamical environment which varies in size and magnitude due to&#160; both&#160; planetary period oscillations and solar-driven storms. &#160;

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On the pipeline polarization in the case of insulation delamination from its surface

Uspihi materialoznavstva ◽

10.15407/materials2020.01.040 ◽

2020 ◽

Vol 2020 (1) ◽

pp. 40-45

Author(s):

V. V. Lukovych ◽

Keyword(s):

Current Density ◽

Cathodic Protection ◽

Polarization Potential ◽

Polarization Current ◽

Protection Zone ◽

Average Value ◽

The Earth ◽

First Case ◽

The Difference ◽

Protection Potential

The cathodic protection parameters for two pipelines with a diameter of 1420 mm were calculated. The protection zone for the first pipeline is 6 km long and for the second one it is 5 km. The cathode station current is 12,9 A for the first pipeline and 4 A for the second one. There are a damage and detachment of pipeline insulation, andconsequently a thin layer of electrolyte is located in the detachment area between the metal surface and the insulation. Almost the entire surface of the pipeline has polarization potential. For the first pipeline, the values of the protection potential at neighboring measurement points change quite dramatically, the difference between them can reach tenths of a volt. The polarization current density at the ends of the protection zone is quite small, and accordingly the polarization potential is close to the corrosion potential. But in the vicinity of the drainage point, these values are much larger. The situation is almost the opposite for the second pipeline, where the cathode station current is 4 A. The current density is almost equally distributed throughout the protection zone, slightly larger at its ends. The polarization potential changes accordingly. Its values are larger than the first case. In the cathodic protection, the potential of the pipeline relative to ground zero is important. Its average value depends on the magnitude of the cathode station current. Its graph intersects the lower part of the protection potential graph in the first case and the middle of the graph in the second. The protection potential is the difference between the potential of the pipeline and the earth surface. In the first case, in the vicinity of the drainage point this difference is much larger inside compared to the ends of the zone. As a conclusion, in the practice of cathodic protection it is important to regulate the value of the cathode station current in order to achieve the optimum protection. Keywords: delamination, protection potential, polarization current density.

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Derivation of the full current density vector in the Earth's ionosphere low- and mid-latitude F region using ESA's Swarm satellites

10.5194/egusphere-egu2020-14042 ◽

2020 ◽

Author(s):

Martin Fillion ◽

Gauthier Hulot ◽

Patrick Alken ◽

Arnaud Chulliat ◽

Pierre Vigneron

Keyword(s):

Current Density ◽

Current System ◽

Three Dimensional ◽

Current Density Vector ◽

F Region ◽

Swarm Satellites ◽

Density Vector ◽

Dynamical Features ◽

The One ◽

Swarm Satellite

A new multi-spacecraft method to recover estimates of the average three-dimensional current density in the Earth's ionosphere is presented. It is demonstrated using the ESA's Swarm satellite constellation and by taking advantage of the favorable geometrical configurations during the early phase of the mission. The current density vector is calculated inside prisms whose vortices are defined by the satellite positions. The mathematical formalism differs from previous approaches such as the one known as the &#8221;curlometer&#8221;. It makes use of the well-known curl-B technique and involves an inverse problem which allows for error propagation through the calculation. Data from the vector field magnetometers of the three satellites are used and special care is taken to characterize the errors on these data. The method is applied in the low- and mid-latitude F-region on 15 February 2014. It provides latitudinal profiles of the full current density vector together with the associated error bars in the morning and evening sectors. We observe several dynamical features such as clear signatures of field-aligned interhemispheric currents, potential signatures of the wind dynamo current system as well as mid-latitude east-west currents.

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From the Sun to the Earth: August 25, 2018 geomagnetic storm effects

10.5194/egusphere-egu2020-1416 ◽

2020 ◽

Author(s):

Mirko Piersanti ◽

Paola De Michelis ◽

Dario Del Moro ◽

Roberta Tozzi ◽

Michael Pezzopane ◽

...

Keyword(s):

Geomagnetic Storm ◽

Interplanetary Space ◽

Current System ◽

The Sun ◽

Geomagnetically Induced Currents ◽

Instrumental Approach ◽

Sequence Of Events ◽

The Earth ◽

Mass Ejection ◽

European Sector

On August 25, 2018 the interplanetary counterpart of the August 20, 2018 Coronal Mass Ejection (CME) hit the Earth, giving rise to a strong geomagnetic storm. We present a description of the whole sequence of events from the Sun to the ground as well as a detailed analysis of the onserved effects on the Earth's environment by using a multi instrumental approach. We studied the ICME propagation in the interplanetary space up to the analysis of its effects in the magnetosphere, ionosphere and at ground. To accomplish this task, we used ground and space collected data, including data from CSES (China Seismo Electric Satellite), launched on February 11, 2018. We found a direct connection between the ICME impact point onto the magnetopause and the pattern of the Earth's polar electrojects. Using the Tsyganenko TS04 model prevision, we were able to correctly identify the principal magnetospheric current system activating during the different phases of the geomagnetic storm. Moreover, we analyzed the space-weather effects associated with the August 25, 2018 solar event in terms of evaluation geomagnetically induced currents (GIC) and identification of possible GPS loss of lock. We found that, despite the strong geomagnetic storm, no loss of lock has been detected. On the contrary, the GIC hazard was found to be potentially more dangerous than other past, more powerful solar events, such as the St. Patrick geomagnetic storm, especially at latitudes higher than $60^\circ$ in the European sector.

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ON THE FIELD DUE TO A VERTICAL LINE SOURCE OF CURRENT GROUNDED TO EARTH

Geophysics ◽

10.1190/1.1439469 ◽

1938 ◽

Vol 3 (1) ◽

pp. 58-62 ◽

Cited By ~ 2

Author(s):

Solomon Bilinsky

Keyword(s):

Current Density ◽

Line Source ◽

Vertical Component ◽

Radial Component ◽

Vertical Line ◽

Displacement Current ◽

The Earth ◽

Density Vector ◽

Vertical Wire ◽

A Current

An expression for the current density at any point in the earth due to a current in an infinitely long vertical wire is found for two types of current: (1) Simply periodic, (2) Rectangular impulse. These are given respectively by equations (11) and (13) below, where [Formula: see text] is the horizontal radial component and [Formula: see text] the vertical component of the current density vector at the point (r, z), which is at a distance R from the grounding point. These formulas hold for frequencies not too high or times not too small to allow neglect of the displacement current.

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POTENTIAL AND APPARENT RESISTIVITY OVER DIPPING BEDS

Geophysics ◽

10.1190/1.1438275 ◽

1956 ◽

Vol 21 (3) ◽

pp. 780-793 ◽

Cited By ~ 13

Author(s):

Jerome Chastenet De Gery ◽

Geza Kunetz

Keyword(s):

Point Source ◽

Current Density ◽

Potential Field ◽

Apparent Resistivity ◽

Exact Expression ◽

Electrode Configuration ◽

Vertical Profiles ◽

The Earth ◽

Electrode Separation

The potential field due to a point source of current, located on the surface of the earth near a dipping bed, is given in an exact expression and modified expressions are developed for computations. These expressions lead to graphs of the potential field and to apparent resistivity vertical profiles which are presented. The Schlumberger electrode configuration is used. This configuration consists of two current electrodes and two potential electrodes, the latter placed close enough together that the current density between them can be considered to be uniform. With this configuration oriented perpendicular to the strike of the dipping bed, the apparent resistivity is paradoxical in that it approaches either zero or infinity as the electrode separation increases without limit.

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