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

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

<p>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 ”curlometer”. 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.</p>

scholarly journals The equatorial E-region and its plasma instabilities: a tutorial

2009 ◽  
Vol 27 (4) ◽  
pp. 1509-1520 ◽  
Author(s):  
D. T. Farley
Keyword(s):  
Current System ◽  
Three Dimensional ◽  
Plasma Instabilities ◽  
Basic Physics ◽  
Electrojet Current ◽  
Fluid Theory ◽  
E Region ◽  
Kinetic Effects ◽  
The One ◽  
Observational Techniques

Abstract. In this short tutorial we first briefly review the basic physics of the E-region of the equatorial ionosphere, with emphasis on the strong electrojet current system that drives plasma instabilities and generates strong plasma waves that are easily detected by radars and rocket probes. We then discuss the instabilities themselves, both the theory and some examples of the observational data. These instabilities have now been studied for about half a century (!), beginning with the IGY, particularly at the Jicamarca Radio Observatory in Peru. The linear fluid theory of the important processes is now well understood, but there are still questions about some kinetic effects, not to mention the considerable amount of work to be done before we have a full quantitative understanding of the limiting nonlinear processes that determine the details of what we actually observe. As our observational techniques, especially the radar techniques, improve, we find some answers, but also more and more questions. One difficulty with studying natural phenomena, such as these instabilities, is that we cannot perform active cause-and-effect experiments; we are limited to the inputs and responses that nature provides. The one hope here is the steadily growing capability of numerical plasma simulations. If we can accurately simulate the relevant plasma physics, we can control the inputs and measure the responses in great detail. Unfortunately, the problem is inherently three-dimensional, and we still need somewhat more computer power than is currently available, although we have come a long way.

scholarly journals THE ELECTRICAL CURRENT DENSITY VECTOR IN THE INNER PENUMBRA OF A SUNSPOT

2010 ◽  
Vol 721 (1) ◽  
pp. L58-L61 ◽  
Author(s):  
K. G. Puschmann ◽  
B. Ruiz Cobo ◽  
V. Martínez Pillet
Keyword(s):  
Current Density ◽  
Electrical Current ◽  
Current Density Vector ◽  
Density Vector ◽  
Electrical Current Density

scholarly journals Electro-plastic metal cutting

2019 ◽  
Vol 75 (6) ◽  
pp. 735-740
Author(s):  
O. A. Troitskii ◽  
V. I. Stashenko
Keyword(s):  
Cast Iron ◽  
Friction Force ◽  
Current Density ◽  
Metal Cutting ◽  
Pulse Current ◽  
High Strength ◽  
Heating Zone ◽  
Current Density Vector ◽  
Plastic Metal ◽  
Density Vector

In the process of cutting of steels, high strength and heat-resistant alloys a strong warming-up of the cutting instrument takes place, necessitating its cooling by special emulsions and resulting in quick wear and increase of products cost. It was determined by experiment, that during a metal with current cutting, an electro-plastic effect arises. During the lector-plastic cutting, the plastic deformation of a metal under pulse current effect becomes easier, making the friction force between the metal chips and the cutting instrument front edge lower. The electro-plastic metal cutting method accounting the current polarity, current density vector directions, as well as pulse current parameters, can considerably improve the cut surface microstructure and increase the instrument service life. At that, the thermal regime of the cutting can be lowered due to cutting force lowering and heating zone shifting inside the piece or the instrument due to Thomson effect. It was shown, that during the electro-plastic metal cutting the friction force can decrease by 25–30% at the favorable current density vector orientation, as it takes place during electro-static metal drawing and rolling. The current plasticizing action results in decreasing friction force and the chips twisting radius, which can be confluent even for cast iron. At the example of metal drilling with the pulse current, the important current effects on the cutting mechanical parameters revealed. The conditions of metal electro-plastic cutting stated. Results of the experiment study of metal electro-plastic cutting quoted for the processes of steel and cast iron drilling.

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

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

<p>The ring current is an important part of the large-scale magnetosphere-ionosphere current system; mainly concentrated in the equatorial plane, between 2-7 R<sub>E</sub>, and strongly ordered between ± 30 ° 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.</p>

scholarly journals Transient production of F-region irregularities associated with TCV passage

2003 ◽  
Vol 21 (7) ◽  
pp. 1531-1541 ◽  
Author(s):  
R. Kataoka ◽  
H. Fukunishi ◽  
K. Hosokawa ◽  
H. Fujiwara ◽  
A. S. Yukimatu ◽  
...  
Keyword(s):  
Electric Fields ◽  
Current System ◽  
Rapid Evolution ◽  
Three Dimensional ◽  
Leading Edge ◽  
Spectral Width ◽  
Plasma Convection ◽  
Plasma Irregularities ◽  
F Region ◽  
Field Aligned Current

Abstract. Transient production of F-region plasma irregularities due to traveling convection vortices (TCVs) was investigated using the Super Dual Auroral Radar Network (SuperDARN) combined with ground magnetometer networks and the POLAR ultraviolet imager. We selected two large-amplitude (100–200 nT) TCV events that occurred on 22 May 1996 and 24 July 1996. It is found that the TCV-associated HF backscatter arises in blobs with spatial scale of a few hundreds km. They traveled following tailward bulk motion of the TCV across the three fields-of-view of the SuperDARN HF radars in the prenoon sector. The spectra in the blobs showed unidirectional Doppler velocities of typically 400–600 m/s, with flow directions away from the radar. These unidirectional velocities correspond to the poleward and/or eastward convective flow near the leading edge of upward field-aligned current. The backscatter blobs overlapped the poleward and westward part of the TCV-related transient aurora. It is likely that the transient backscatter blobs are produced by the three-dimensional gradient drift instabilities in the three-dimensional current system of the TCV. In this case, nonlinear rapid evolution of irregularities would occur in the upward field-aligned current region. The spectral width of the backscatter blob is typically distributed between 50 and 300 m/s, but sometimes it is over 400 m/s. This suggests that the temporal broad spectra over 400 m/s are produced by Pc1–2 bursts, while the background spectral width of 50–300 m/s are produced by the velocity gradient structure of convection vortices themselves.Key words. Ionosphere (Electric fields and currents; Ionospheric irregularities; Plasma convection)

scholarly journals Excitation of zero-frequency magnetic field-aligned currents by ionospheric heating

2011 ◽  
Vol 29 (6) ◽  
pp. 1147-1152 ◽  
Author(s):  
A. V. Streltsov ◽  
T. R. Pedersen
Keyword(s):  
Magnetic Field ◽  
Current System ◽  
Three Dimensional ◽  
Characteristic Size ◽  
Ionospheric Heating ◽  
F Region ◽  
Strong Localization ◽  
Frequency Magnetic Field ◽  
Shear Alfven Waves ◽  
Zero Frequency

Abstract. Time-dependent, three-dimensional numerical simulations of the reduced MHD model describing shear Alfvén waves in the magnetosphere provide an interesting prediction superficially similar to results of several ionospheric heating experiments conducted at high altitudes. In these experiments, heating of the ionospheric F-region with a constant/zero-frequency beam of HF waves causes luminous structures in the ionosphere in the form of a ring or a solid spot with a characteristic size comparable to the size of the heated spot. Simulations suggest that spots/rings or similar optical appearance might be associated with a magnetic field-aligned current system produced by the ionospheric heating. Two of the most interesting features of this current system are (1) strong localization across the ambient magnetic field and (2) distinctive non-symmetrical luminous signatures (ring/spot) in magnetically conjugate locations in the ionosphere.

scholarly journals A comparative analysis between classical and modified approach of description of the electrical machine windings by means of T0 method

Open Physics ◽  
2017 ◽  
Vol 15 (1) ◽  
pp. 918-923
Author(s):  
Rafał M. Wojciechowski ◽  
Cezary Jędryczka
Keyword(s):  
Comparative Analysis ◽  
Current Density ◽  
Electrical Machines ◽  
Electrical Machine ◽  
Current Density Vector ◽  
Edge Element ◽  
Classical Formulation ◽  
Density Vector ◽  
Element Method

AbstractThis paper deals with comparative analysis between classical and modified approach of description of electrical machines windings by means of theT0method. The classical formulation (CF) ofT0method in which the distribution of the turns in the winding is treated the same as naturally determined current paths has been compared to the modified formulation (MF), in which by incorporating coefficients differencing the conductivity the homogeneity of the current density vectorJ0,i.e. turns distribution is achieved. The method of calculating the coefficients correcting the conductivities for the MF approach has been presented. For solving ofT0method equations, the edge element method (EEM) has been incorporated.

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