scholarly journals DRIFT-ALFVEN INSTABILITY IN A 2D MAGNETOTAIL CONFIGURATION – THE ADDITION OF BOUNCING ELECTRONS

2019 ◽  
Vol 47 (1) ◽  
pp. 127-128
Author(s):  
O.O. Tsareva ◽  
G. Fruit ◽  
P. Louarn ◽  
A. Tur
Keyword(s):  
Growth Rate ◽  
Current Sheet ◽  
Density Gradient ◽  
Resonant Interaction ◽  
High Plasma ◽  
High Plasma Density ◽  
Instability Growth ◽  
Dipole Configuration ◽  
Diamagnetic Drift ◽  
Magnetic Equilibrium

To explain the possible destabilization of a 2D magnetic equilibrium such as the Near-Earth magnetotail, we developed a kinetic model describing the resonant interaction of electromagnetic fluctuations and bouncing electrons trapped in the magnetosphere, characterized by a high plasma density gradient. A small-β approximation is used in agreement with a small field line curvature. It has been found that for a quasi-dipole configuration, unstable electromagnetic modes may develop in the current sheet in westward direction with a growth rate of the order of a few tenth of seconds provided that the typical scale of density gradient slope responsible for the diamagnetic drift effects is over one Earth radius or less. This instability growth rate is large enough to destabilise the current sheet on time scales often observed during substorm onset.

scholarly journals Electromagnetic drift instability in a two-dimensional magnetotail – the addition of bouncing electrons

2019 ◽  
Vol 85 (2) ◽  
Author(s):  
O. Tsareva ◽  
G. Fruit ◽  
P. Louarn ◽  
A. Tur
Keyword(s):  
Growth Rate ◽  
Current Sheet ◽  
Resonant Interaction ◽  
Plasma Pressure ◽  
Two Dimensional ◽  
Instability Growth ◽  
Field Lines ◽  
Magnetic Bottle ◽  
Drift Instability ◽  
Diamagnetic Drift

To explain the possible destabilization of a two-dimensional magnetic equilibrium such as the near-Earth magnetotail, we developed a kinetic model describing the resonant interaction of electromagnetic fluctuations and bouncing electrons trapped in the magnetic bottle. A small-$\unicode[STIX]{x1D6FD}$approximation (i.e., the plasma pressure is lower than the magnetic pressure) is used in agreement with a small field line curvature. The linearized gyro-kinetic Vlasov equation is integrated along the unperturbed particle trajectories, including cyclotron and bounce motions. The dispersion relation for drift-Alfvèn waves is obtained through the plasma quasi-neutrality condition and Ampere’s law for the parallel current. It has been found that for a quasi-dipolar configuration ($\text{L}\sim 8$corresponds to the set of the Earth’s magnetic field lines, crossing the Earths magnetic equator at 8 Earth radii), unstable electromagnetic modes may develop in the current sheet with a growth rate of the order of a few tenths of a second provided that the typical scale of density gradient slope responsible for the diamagnetic drift effects is over one Earth radius or less. This instability growth rate is large enough to destabilize the current sheet on time scales of 2–4 minutes as observed during substorm onset.

scholarly journals The Quantum Effects Role on Weibel Instability Growth Rate in Dense Plasma

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
M. Mahdavi ◽  
F. Khodadadi Azadboni
Keyword(s):  
Growth Rate ◽  
Density Gradient ◽  
Energy Deposition ◽  
Quantum Effects ◽  
Instability Growth Rate ◽  
Tunneling Effect ◽  
Deposition Mechanism ◽  
Weibel Instability ◽  
Density Perturbations ◽  
Instability Growth

The Weibel instability is one of the basic plasma instabilities that plays an important role in stopping the hot electrons and energy deposition mechanism. In this paper, combined effect of the density gradient and quantum effects on Weibel instability growth rate is investigated. The results have shown that, by increasing the quantum parameter, for large wavelengths, the Weibel instability growth rate shrinks to zero. In the large wavelengths limit, the analysis shows that quantum effects and density gradient tend to stabilize the Weibel instability. The density perturbations have decreased the growth rate of Weibel instability in the near corona fuel,η>0.1. In the small wavelengths limit, for the density gradient,η<0.1, the tunneling quantum effects increase anisotropy in the phase space. The quantum tunneling effect leads to an unexpected increase in the Weibel instability growth rate.

Extraction of single-ion beams from helicon ion source in high plasma density operation mode: Experiment and simulation

2006 ◽  
Vol 77 (3) ◽  
pp. 03B901 ◽  
Author(s):  
S. Mordyk ◽  
V. Miroshnichenko ◽  
A. Nahornyy ◽  
D. Nahornyy ◽  
D. Shulha ◽  
...  
Keyword(s):  
Plasma Density ◽  
Operation Mode ◽  
High Plasma ◽  
Ion Beams ◽  
Ion Source ◽  
High Plasma Density ◽  
Experiment And Simulation

Suppression of Baroclinic Instabilities in Buoyancy-Driven Flow over Sloping Bathymetry

2017 ◽  
Vol 47 (1) ◽  
pp. 49-68 ◽  
Author(s):  
Robert D. Hetland
Keyword(s):  
Growth Rate ◽  
Linear Instability ◽  
Linear Stability Theory ◽  
Buoyancy Frequency ◽  
Bottom Slope ◽  
Coriolis Parameter ◽  
Plume Front ◽  
Instability Theory ◽  
Instability Growth ◽  
Flow Configurations

AbstractBaroclinic instabilities are ubiquitous in many types of geostrophic flow; however, they are seldom observed in river plumes despite strong lateral density gradients within the plume front. Supported by results from a realistic numerical simulation of the Mississippi–Atchafalaya River plume, idealized numerical simulations of buoyancy-driven flow are used to investigate baroclinic instabilities in buoyancy-driven flow over a sloping bottom. The parameter space is defined by the slope Burger number S = Nf−1α, where N is the buoyancy frequency, f is the Coriolis parameter, and α is the bottom slope, and the Richardson number Ri = N2f2M−4, where M2 = |∇Hb| is the magnitude of the lateral buoyancy gradients. Instabilities only form in a subset of the simulations, with the criterion that SH ≡ SRi−1/2 = Uf−1W−1 = M2f−2α 0.2, where U is a horizontal velocity scale and SH is a new parameter named the horizontal slope Burger number. Suppression of instability formation for certain flow conditions contrasts linear stability theory, which predicts that all flow configurations will be subject to instabilities. The instability growth rate estimated in the nonlinear 3D model is proportional to ωImaxS−1/2, where ωImax is the dimensional growth rate predicted by linear instability theory, indicating that bottom slope inhibits instability growth beyond that predicted by linear theory. The constraint SH 0.2 implies a relationship between the inertial radius Li = Uf−1 and the plume width W. Instabilities may not form when 5Li > W; that is, the plume is too narrow for the eddies to fit.

scholarly journals The Study of Thermal Conditions on Weibel Instability

2015 ◽  
Vol 2015 ◽  
pp. 1-6
Author(s):  
M. Mahdavi ◽  
H. Khanzadeh
Keyword(s):  
Growth Rate ◽  
Thermal Conditions ◽  
Ion Scattering ◽  
Weibel Instability ◽  
Anisotropic Temperature ◽  
Instability Growth ◽  
Limiting Condition ◽  
Limiting Case ◽  
Background Ions ◽  
Electromagnetic Instability

Weibel electromagnetic instability has been studied analytically in relativistic plasma with high parallel temperature, where|α=(mc2/T∥)(1+p^⊥2/m2c2)1/2|≪1and while the collision effects of electron-ion scattering have also been considered. According to these conditions, an analytical expression is derived for the growth rate of the Weibel instability for a limiting case of|ζ=α/2(ω′/ck)|≪1, whereω′is the sum of the wave frequency of instability and the collision frequency of electrons with background ions. The results show that in the limiting conditionα≪1there is an unusual situation of the Weibel instability so thatT∥≫T⊥, while in the classic Weibel instabilityT∥≪T⊥. The obtained results show that the growth rate of the Weibel instability will be decreased due to an increase in the number of collisions and a decrease in the anisotropic temperature by the increasing of plasma density, while the increase of the parameterγ^⊥=(1+p^⊥2/m2c2)1/2leads to the increase of the Weibel instability growth rate.

scholarly journals Orbit width scaling of TAE instability growth rate

1995 ◽  
Author(s):  
H.V. Wong ◽  
H.L. Berk ◽  
B.N. Breizman
Keyword(s):  
Growth Rate ◽  
Instability Growth Rate ◽  
Instability Growth
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