Non-Neutral Field-Aligned Current Sheet and Auroral Electric Field.

1979 ◽  
Author(s):  
R. K. Albano ◽  
L. C. Lee ◽  
J. R. Kan
Keyword(s):  
Electric Field ◽  
Current Sheet ◽  
Neutral Field ◽  
Field Aligned Current

scholarly journals Localized fast flow disturbance observed in the plasma sheet and in the ionosphere

2005 ◽  
Vol 23 (2) ◽  
pp. 553-566 ◽  
Author(s):  
R. Nakamura ◽  
O. Amm ◽  
H. Laakso ◽  
N. C. Draper ◽  
M. Lester ◽  
...  
Keyword(s):  
Spatial Scale ◽  
Current Sheet ◽  
Plasma Sheet ◽  
Time Scale ◽  
Ionospheric Disturbance ◽  
Flow Shear ◽  
Current Location ◽  
Field Aligned Current ◽  
Temporal And Spatial ◽  
Fast Flow

Abstract. An isolated plasma sheet flow burst took place at 22:02 UT, 1 September 2002, when the Cluster footpoint was located within the area covered by the Magnetometers-Ionospheric Radars-All-sky Cameras Large Experiment (MIRACLE). The event was associated with a clear but weak ionospheric disturbance and took place during a steady southward IMF interval, about 1h preceding a major substorm onset. Multipoint observations, both in space and from the ground, allow us to discuss the temporal and spatial scale of the disturbance both in the magnetosphere and ionosphere. Based on measurements from four Cluster spacecraft it is inferred that Cluster observed the dusk side part of a localized flow channel in the plasma sheet with a flow shear at the front, suggesting a field-aligned current out from the ionosphere. In the ionosphere the equivalent current pattern and possible field-aligned current location show a pattern similar to the auroral streamers previously obtained during an active period, except for its spatial scale and amplitude. It is inferred that the footpoint of Cluster was located in the region of an upward field-aligned current, consistent with the magnetospheric observations. The entire disturbance in the ionosphere lasted about 10min, consistent with the time scale of the current sheet disturbance in the magnetosphere. The plasma sheet bulk flow, on the other hand, had a time scale of about 2min, corresponding to the time scale of an equatorward excursion of the enhanced electrojet. These observations confirm that localized enhanced convection in the magnetosphere and associated changes in the current sheet structure produce a signature with consistent temporal and spatial scale at the conjugate ionosphere.

scholarly journals Numerical analysis of global ionospheric current system including the effect of equatorial enhancement

1999 ◽  
Vol 17 (5) ◽  
pp. 692-706 ◽  
Author(s):  
S. Tsunomura
Keyword(s):  
Magnetic Fields ◽  
Electric Field ◽  
Current System ◽  
Equatorial Region ◽  
Iri Model ◽  
Ionospheric Layer ◽  
Ionospheric Current ◽  
New Model ◽  
Ionospheric Current System ◽  
Field Aligned Current

Abstract. A modeling method is proposed to derive a two-dimensional ionospheric layer conductivity, which is appropriate to obtain a realistic solution of the polar-originating ionospheric current system including equatorial enhancement. The model can be obtained by modifying the conventional, thin shell conductivity model. It is shown that the modification for one of the non-diagonal terms (Σθφ) in the conductivity tensor near the equatorial region is very important; the term influences the profile of the ionospheric electric field around the equator drastically. The proposed model can reproduce well the results representing the observed electric and magnetic field signatures of geomagnetic sudden commencement. The new model is applied to two factors concerning polar-originating ionospheric current systems. First, the latitudinal profile of the DP2 amplitude in the daytime is examined, changing the canceling rate for the dawn-to-dusk electric field by the region 2 field-aligned current. It is shown that the equatorial enhancement would not appear when the ratio of the total amount of the region 2 field-aligned current to that of region 1 exceeds 0.5. Second, the north-south asymmetry of the magnetic fields in the summer solstice condition of the ionospheric conductivity is examined by calculating the global ionospheric current system covering both hemispheres simultaneously. It is shown that the positive relationship between the magnitudes of high latitude magnetic fields and the conductivity is clearly seen if a voltage generator is given as the source, while the relationship is vague or even reversed for a current generator. The new model, based on the International Reference Ionosphere (IRI) model, can be applied to further investigations in the quantitative analysis of the magnetosphere-ionosphere coupling problems.Key words. Ionosphere (electric fields and currents; equatorial ionosphere; ionosphere-magnetosphere interactions)

Field-aligned current, convective electric field, and auroral particle measurements during a major magnetic storm

1981 ◽  
Vol 86 (A7) ◽  
pp. 5561 ◽  
Author(s):  
B. M. Shuman ◽  
R. P. Vancour ◽  
M. Smiddy ◽  
N. A. Saflekos ◽  
F. J. Rich
Keyword(s):  
Electric Field ◽  
Magnetic Storm ◽  
Particle Measurements ◽  
Field Aligned Current

scholarly journals On the possibility of using an electromagnetic ionosphere in global MHD simulations

1998 ◽  
Vol 16 (4) ◽  
pp. 397-402 ◽  
Author(s):  
P. Janhunen
Keyword(s):  
Electric Field ◽  
Source Term ◽  
Interaction Space ◽  
Mhd Equations ◽  
Coupling Scheme ◽  
Simulation Studies ◽  
Mhd Simulations ◽  
Field Aligned Current ◽  
Flow Of Information ◽  
Ionospheric Potential

Abstract. Global magnetohydrodynamic (MHD) simulations of the Earth's magnetosphere must be coupled with a dynamical ionospheric module in order to give realistic results. The usual approach is to compute the field-aligned current (FAC) from the magnetospheric MHD variables at the ionospheric boundary. The ionospheric potential is solved from an elliptic equation using the FAC as a source term. The plasma velocity at the boundary is the E × B velocity associated with the ionospheric potential. Contemporary global MHD simulations which include a serious ionospheric model use this method, which we call the electrostatic approach in this paper. We study the possibility of reversing the flow of information through the ionosphere: the magnetosphere gives the electric field to the ionosphere. The field is not necessarily electrostatic, thus we will call this scheme electromagnetic. The electric field determines the horizontal ionospheric current. The divergence of the horizontal current gives the FAC, which is used as a boundary condition for MHD equations. We derive the necessary formulas and discuss the validity of the approximations necessarily involved. It is concluded that the electromagnetic ionosphere-magnetosphere coupling scheme is a serious candidate for future global MHD simulators, although a few problem areas still remain. At minimum, it should be investigated further to discover whether there are any differences in the simulation using the electrostatic or the electromagnetic ionospheric coupling.Key words. Ionosphere · Ionosphere-magnetosphere interaction · Magnetospheric physics · Magnetosphere-ionosphere interaction · Space plasma physics · Numerical simulation studies

Antarctic polar plateau vertical electric field variations across heliocentric current sheet crossings

2006 ◽  
Vol 68 (6) ◽  
pp. 639-654 ◽  
Author(s):  
G.B. Burns ◽  
B.A. Tinsley ◽  
A.R. Klekociuk ◽  
O.A. Troshichev ◽  
A.V. Frank-Kamenetsky ◽  
...  
Keyword(s):  
Electric Field ◽  
Current Sheet ◽  
Vertical Electric Field

scholarly journals Investigation on High Velocity Plasmas and Field Aligned Currents at High Latitudes

2020 ◽  
pp. 22-29
Author(s):  
J. C. K. Akhila ◽  
C. P. Anil Kumar
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
High Velocity ◽  
Transmission Function ◽  
External Loading ◽  
Plasma Parameters ◽  
Spherical Cap ◽  
Field Aligned Current ◽  
Field Lines ◽  
Spherical Cap Harmonic Analysis

The interaction of high velocity plasma with Earth’s magnetic field is fundamental and offer many questions on high latitude electrodynamics. The problems associated with influence of electric field and Field Aligned Current (FAC) generation is investigated with the aid of spherical cap harmonic analysis at 830 Mag. Lat. in southern hemispheres. The investigation is done on the cases with different Interplanetary Magnetic Field (IMF) conditions after the earth directed solar events. The helio-plasma parameters viz., density, velocity, energy, electron temperature are also noted during the field aligned current studies. It seems that, due to external magnetic field influence polarization of plasma electric field take place (reorientation of the convective cells). It happens with different orientation as per the magnitude and direction of By and Bz component and the horizontal currents. It is noted that the FAC value also depends on kinetic energy of the plasma streams and conductivity of external loading. As the plasma decelerates by force Jsw X Esw, the resultant current may extend along the field lines. Increases in the FAC density are seemed to be proportional to the transmission function.

scholarly journals Quantitative modelling of the closure of meso-scale parallel currents in the nightside ionosphere

2004 ◽  
Vol 22 (1) ◽  
pp. 125-140 ◽  
Author(s):  
A. Marchaudon ◽  
J.-C. Cerisier ◽  
O. Amm ◽  
M. Lester ◽  
C. W. Carlson ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Satellite Orbit ◽  
Precipitation Pattern ◽  
Field Gradients ◽  
Southward Shift ◽  
Field Aligned Current ◽  
Electric Field Profile ◽  
Electric Fields And Currents ◽  
Meso Scale

Abstract. On 12 January 2000, during a northward IMF period, two successive conjunctions occur between the CUTLASS SuperDARN radar pair and the two satellites Ørsted and FAST. This situation is used to describe and model the electrodynamic of a nightside meso-scale arc associated with a convection shear. Three field-aligned current sheets, one upward and two downward on both sides, are observed. Based on the measurements of the parallel currents and either the conductance or the electric field profile, a model of the ionospheric current closure is developed along each satellite orbit. This model is one-dimensional, in a first attempt and a two-dimensional model is tested for the Ørsted case. These models allow one to quantify the balance between electric field gradients and ionospheric conductance gradients in the closure of the field-aligned currents. These radar and satellite data are also combined with images from Polar-UVI, allowing for a description of the time evolution of the arc between the two satellite passes. The arc is very dynamic, in spite of quiet solar wind conditions. Periodic enhancements of the convection and of electron precipitation associated with the arc are observed, probably associated with quasi-periodic injections of particles due to reconnection in the magnetotail. Also, a northward shift and a reorganisation of the precipitation pattern are observed, together with a southward shift of the convection shear. Key words. Ionosphere (auroral ionosphere; electric fields and currents; particle precipitation) – Magnetospheric physics (magnetosphere-ionosphere interactions)

scholarly journals Particle acceleration in a reconnecting current sheet: PIC simulation

2009 ◽  
Vol 75 (5) ◽  
pp. 619-636 ◽  
Author(s):  
TARAS V. SIVERSKY ◽  
VALENTINA V. ZHARKOVA
Keyword(s):  
Electric Field ◽  
Energy Distribution ◽  
Current Sheet ◽  
Plasma Density ◽  
Three Dimensional ◽  
Polarization Field ◽  
Electron Mass ◽  
Langmuir Waves ◽  
Particle In Cell ◽  
Reconnecting Current Sheet

AbstractThe acceleration of protons and electrons in a reconnecting current sheet (RCS) is simulated with a particle-in-cell (PIC) 2D3V (two-dimensional in space and three-dimensional in velocity space) code for the proton-to-electron mass ratio of 100. The electromagnetic configuration forming the RCS incorporates all three components of the magnetic field (including the guiding field) and a drifted electric field. PIC simulations reveal that there is a polarization electric field that appears during acceleration owing to a separation of electrons from protons towards the midplane of the RCS. If the plasma density is low, the polarization field is weak and the particle trajectories in the PIC simulations are similar to those in the test particle (TP) approach. For the higher plasma density the polarization field is stronger and it affects the trajectories of protons by increasing their orbits during acceleration. This field also leads to a less asymmetrical abundance of ejected protons towards the midplane in comparison with the TP approach. For a given magnetic topology electrons in PIC simulations are ejected to the same semispace as protons, in contrast to the TP results. This happens because the polarization field extends far beyond the thickness of a current sheet. This field decelerates the electrons, which are initially ejected into the semispace opposite to the protons, returns them back to the RCS, and, eventually, leads to the electron ejection into the same semispace as protons. The energy distribution of the ejected electrons is rather wide and single-peaked, in contrast to the two-peak narrow-energy distribution obtained in the TP approach. In the case of a strong guiding field, the mean energy of the ejected electrons is found to be smaller than it is predicted analytically and by the TP simulations. The beam of accelerated electrons is also found to generate turbulent electric field in the form of Langmuir waves.

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