Ion temperature drop and quasi-electrostatic electric field at the current sheet boundary minutes prior to the local current disruption

2009 ◽  
Vol 114 (A10) ◽  
pp. n/a-n/a ◽  
Author(s):  
Jun Liang ◽  
W. W. Liu ◽  
E. F. Donovan
Keyword(s):  
Electric Field ◽  
Current Sheet ◽  
Temperature Drop ◽  
Ion Temperature ◽  
Current Disruption ◽  
Local Current

scholarly journals Disruption of magnetospheric current sheet by quasi-electrostatic field

2009 ◽  
Vol 27 (5) ◽  
pp. 1941-1950 ◽  
Author(s):  
W. W. Liu ◽  
J. Liang
Keyword(s):  
Current Sheet ◽  
Drift Velocity ◽  
Electrostatic Field ◽  
Numerical Solutions ◽  
External Perturbation ◽  
Ion Drift ◽  
Current Disruption ◽  
Local Current ◽  
Fluid Theory ◽  
Two Fluid

Abstract. Recent observational evidence has indicated that local current sheet disruptions are excited by an external perturbation likely associated with the kinetic ballooning (KB) instability initiating at the transition region separating the dipole- and tail-like geometries. Specifically a quasi-electrostatic field pointing to the neutral sheet was identified in the interval between the arrival of KB perturbation and local current disruption. How can such a field drive the local current sheet unstable? This question is considered through a fluid treatment of thin current sheet (TCS) where the generalized Ohm's law replaces the frozen-in-flux condition. A perturbation with the wavevector along the current is applied, and eigenmodes with frequency much below the ion gyrofrequency are sought. We show that the second-order derivative of ion drift velocity along the thickness of the current sheet is a critical stability parameter. In an E-field-free Harris sheet in which the drift velocity is constant, the current sheet is stable against this particular mode. As the electrostatic field grows, however, potential for instability arises. The threshold of instability is identified through an approximate analysis of the theory. For a nominal current sheet half-thickness of 1000 km, the estimated instability threshold is E~4 mV/m. Numerical solutions indicate that the two-fluid theory gives growth rate and wave period consistent with observations.

Observational support for the current sheet catastrophe model of substorm current disruption

1992 ◽  
Vol 19 (16) ◽  
pp. 1635-1638 ◽  
Author(s):  
G. R. Burkhart ◽  
R. E. Lopez ◽  
P. B. Dusenbery ◽  
T. W. Speiser
Keyword(s):  
Current Sheet ◽  
Catastrophe Model ◽  
Current Disruption

scholarly journals Instabilities in a thin current sheet and their consequences

2004 ◽  
Vol 11 (2) ◽  
pp. 153-163 ◽  
Author(s):  
N. Singh
Keyword(s):  
Magnetic Field ◽  
Current Sheet ◽  
Drift Velocity ◽  
Early Stage ◽  
Field Configuration ◽  
Central Plane ◽  
Current Disruption ◽  
Electrons And Ions ◽  
Thin Current Sheet ◽  
Electrostatic Fluctuations

Abstract. Using a fully 3-D particle in-cell simulation, we studied the electrodynamics of a thin current sheet (CS). Starting with a uniform plasma and anti-parallel magnetic field, Harris equilibrium is achieved during the early stage of the simulation. In the processes of reaching the equilibrium, both electrons and ions in the newly formed CS are energized and develop pitch-angle anisotropies. We find two distinct stages of primarily electrostatic instabilities; in the first stage the relative drift between electrons and ions drives the instability in the central regions of the CS. The electrostatic fluctuations scatter electrons causing current disruption in the central region. The associated reduction in the average drift velocity of the current-carrying electrons generates sheared flow. The second stage of the instability begins when the drift velocity develops a minimum in the central plane. Then the shear and the growing electrostatic fluctuations under the condition of the maintained anti-parallel driving magnetic field configuration feed each other making the instability explosive. The growing fluctuations create plasma clumps as the electrons and ions are progressively trapped in the large-amplitude waves. The density clumping also generates clumps in the current. The non-uniform current distribution causes magnetic reconnection, accompanied by heating of electrons and ion at a fast rate and nearly complete bifurcation of the current sheet. Anomalous resistivity during different stages of the evolution of the CS is calculated and compared against theory.

scholarly journals Effect of DC Biased Voltage and Ion Temperature on Bounded Ion-Ion Plasma

2020 ◽  
Vol 25 (1) ◽  
pp. 61-67
Author(s):  
Anish Maskey ◽  
Atit Deuja ◽  
Suresh Basnet ◽  
Raju Khanal
Keyword(s):  
Electric Field ◽  
Strong Electric Field ◽  
Negative Ions ◽  
Simulation Method ◽  
Negative Ion ◽  
Ion Temperature ◽  
Plasma Parameters ◽  
Degree Of Ionization ◽  
Particle In Cell ◽  
Ion Plasma

 A one dimensional particle-in-cell (PIC) simulation method has been employed to study the effect of DC voltage and ion temperature on the properties of ion-ion plasma bounded by two symmetrical but oppositely biased electrodes. It is assumed that the ion-ion plasma is collisionless and both the positive and negative ion species have the same mass, temperature, and degree of ionization. Simulation results show that the formation of sheath and presheath regions and fluctuation of plasma parameters in that region are affected by the biasing voltage and ion temperature. It was found that the magnitude of the electrostatic electric field at the vicinity of biasing electrodes was affected by the biasing voltage and ion temperature as well. This strong electric field close to the electrodes further prevents the flow of charged particles towards the electrodes. The presence of a non-zero electric field at the quasineutral region suggests a presheath region similar to the electron-ion plasma. In the quasineutral region, the density of ions increased with the increase in biasing voltage and decreased with the increase in temperature of isothermal ions. Furthermore, the phase space diagrams for the ions were obtained which indicated different regions of the plasma. The positive ions acquire negative velocity towards the negatively biased electrode and the negative ions acquire positive velocity towards the positively biased electrode.

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

Notched velocity profiles and the radial electric field in high ion temperature plasmas in the Tokamak Fusion Test Reactor

1998 ◽  
Vol 5 (3) ◽  
pp. 665-681 ◽  
Author(s):  
D. R. Ernst ◽  
M. G. Bell ◽  
R. E. Bell ◽  
C. E. Bush ◽  
Z. Chang ◽  
...  
Keyword(s):  
Electric Field ◽  
Radial Electric Field ◽  
Velocity Profiles ◽  
Ion Temperature ◽  
Test Reactor

Comparison of different techniques to estimate the direction of the Poynting vector of EMIC emissions

2021 ◽  
Author(s):  
Benjamin Grison ◽  
Ondrej Santolik
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Poynting Vector ◽  
Source Region ◽  
Transverse Component ◽  
Equatorial Region ◽  
Magnetic Equator ◽  
Ion Temperature ◽  
Temperature Anisotropy ◽  
Single Plane

<p>Electromagnetic Ion Cyclotron (EMIC) waves usually grow in the inner magnetosphere from hot ion temperature anisotropy. The main source region is located close to the magnetic equator and there is a secondary EMIC source region off the magnetic equator in the dayside magnetosphere. The source region can be identified using measurements of the Poynting vector direction.</p><p>The Poynting vector is ideally derived from the measurement of 3 components of the wave electric field and 3 components of components of the wave magnetic field. However, spinning spacecraft often have only two long mutually perpendicular electric antennas in the spin plane, deployed by the centrifugal force. The third antenna, when present, is usually shorter owing to difficulties of deploying a antenna along the spin axis.</p><p>Estimations of the Poynting vector from measurements of three magnetic field components and two electric field components can be obtained assuming the presence of a single plane wave (and thus perpendicularity of the electric field and the magnetic field vectors, according to the Faraday’s law), following the method developed by Loto'aniu et al. (2005). Applying this method to Cluster data, Allen et al. (2013) found the presence of bidirectional EMIC emissions off the magnetic equatorial region.</p><p>Another technique proposed earlier by Santolík et al. (2001) considers the phase shift estimation between the electric signals from each antenna and synthetic perpendicular magnetic field components obtained from the three-dimensional measurements. The method is based on cross-spectral estimates in the frequency domain and can be used to estimate sign of each component of the Poynting vector. Using this technique Grison et al. (2016) showed the importance of the transverse component of the EMIC emissions far from the source region.</p><p>We compare these methods for different events to check how the results of these two techniques differ. We also discuss what we can learn about the EMIC source region from these measurements.</p>

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.

scholarly journals Imaging and EISCAT radar measurements of an auroral prebreakup event

1996 ◽  
Vol 14 (11) ◽  
pp. 1170-1176
Author(s):  
V. Safargaleev ◽  
T. Turunen ◽  
W. Lyatsky ◽  
J. Manninen ◽  
A. Kozlovsky
Keyword(s):  
Electric Field ◽  
Ion Temperature ◽  
Auroral Breakup ◽  
E Region ◽  
Radar Measurements ◽  
Eiscat Radar ◽  
Extended Area ◽  
Auroral Arcs ◽  
Plasma Depletion

Abstract. The results of coordinated EISCAT and TV-camera observations of a prebreakup event on 15 November 1993 have been considered. The variations of the luminosity of two parallel auroral arcs, plasma depletion on the poleward edge of one of these arcs as well as electron and ion temperatures in front of a westward travelling surge were studied. It was found that a short-lived brightening of a weak zenith arc before an auroral breakup was accompanied by fading of an equatorial arc and, vice versa. A plasma depletion in the E region was detected by the EISCAT radar on the poleward edge of the zenith arc just before the auroral breakup. The plasma depletion was associated with an enhancement of ion (at the altitudes of 150–200 km) and electron (in E region) temperatures. During its occurrence, the electric field in the E-region was extremely large (~150 mV/m). A significant increase in ion temperature was also observed 1 min before the arrival of a westward travelling surge (WTS) at the radar zenith. This was interpreted as the existence of an extended area of enhanced electric field ahead of the WTS.

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