scholarly journals CMB temperature anisotropy from broken spatial isotropy due to a homogeneous cosmological magnetic field

2008 ◽  
Vol 78 (6) ◽  
Author(s):  
Tina Kahniashvili ◽  
George Lavrelashvili ◽  
Bharat Ratra
Keyword(s):  
Magnetic Field ◽  
Temperature Anisotropy ◽  
Cmb Temperature

CMB temperature anisotropy

Cosmology ◽  
2017 ◽  
pp. 279-308
Author(s):  
Nicola Vittorio
Keyword(s):  
Temperature Anisotropy ◽  
Cmb Temperature

Maps of the CMB Temperature Anisotropy: from the Time-Ordered Data to the Maximum-Likelihood Solution

2003 ◽  
pp. 414-420
Author(s):  
Radek Stompor ◽  
Amedeo Balbi ◽  
Julian Borrill ◽  
Pedro Ferreira ◽  
Shaul Hanany ◽  
...  
Keyword(s):  
Maximum Likelihood ◽  
Temperature Anisotropy ◽  
Ordered Data ◽  
Cmb Temperature

scholarly journals Proton temperature-anisotropy-driven instabilities in weakly collisional plasmas: Hybrid simulations

2014 ◽  
Vol 81 (1) ◽  
Author(s):  
Petr Hellinger ◽  
Pavel M. Trávníček
Keyword(s):  
Magnetic Field ◽  
Langevin Equation ◽  
Transport Coefficients ◽  
Two Dimensional ◽  
Temperature Anisotropy ◽  
Coulomb Collisions ◽  
Proton Temperature ◽  
Collisionless Plasmas ◽  
High Beta ◽  
Kinetic Instabilities

Kinetic instabilities in weakly collisional, high beta plasmas are investigated using two-dimensional hybrid expanding box simulations with Coulomb collisions modeled through the Langevin equation (corresponding to the Fokker-Planck one). The expansion drives a parallel or perpendicular temperature anisotropy (depending on the orientation of the ambient magnetic field). For the chosen parameters the Coulomb collisions are important with respect to the driver but are not strong enough to keep the system stable with respect to instabilities driven by the proton temperature anisotropy. In the case of the parallel temperature anisotropy the dominant oblique fire hose instability efficiently reduces the anisotropy in a quasilinear manner. In the case of the perpendicular temperature anisotropy the dominant mirror instability generates coherent compressive structures which scatter protons and reduce the temperature anisotropy. For both the cases the instabilities generate temporarily enough wave energy so that the corresponding (anomalous) transport coefficients dominate over the collisional ones and their properties are similar to those in collisionless plasmas.

scholarly journals On a nonlinear state of the electromagnetic ion/ion cyclotron instability

2000 ◽  
Vol 7 (3/4) ◽  
pp. 173-177
Author(s):  
M. Cremer ◽  
M. Scholer
Keyword(s):  
Magnetic Field ◽  
Boundary Layer ◽  
Plasma Sheet ◽  
Large Temperature ◽  
Plasma Sheet Boundary Layer ◽  
Temperature Anisotropy ◽  
Nonlinear Properties ◽  
Cyclotron Instability ◽  
Ion Cyclotron ◽  
The Waves

Abstract. We have investigated the nonlinear properties of the electromagnetic ion/ion cyclotron instability (EMIIC) by means of hybrid simulations (macroparticle ions, massless electron fluid). The instability is driven by the relative (super-Alfvénic) streaming of two field-aligned ion beams in a low beta plasma (ion thermal pressure to magnetic field pressure) and may be of importance in the plasma sheet boundary layer. As shown in previously reported simulations the waves propagate obliquely to the magnetic field and heat the ions in the perpendicular direction as the relative beam velocity decreases. By running the simulation to large times it can be shown that the large temperature anisotropy leads to the ion cyclotron instability (IC) with parallel propagating Alfvén ion cyclotron waves. This is confirmed by numerically solving the electromagnetic dispersion relation. An application of this property to the plasma sheet boundary layer is discussed.

A temperature-anisotropy instability for electromagnetic waves propagating across a static magnetic field

1970 ◽  
Vol 4 (1) ◽  
pp. 13-20 ◽  
Author(s):  
R. W. Landau ◽  
S. Cuperman
Keyword(s):  
Magnetic Field ◽  
Static Magnetic Field ◽  
Electromagnetic Waves ◽  
Maximal Rate ◽  
Temperature Anisotropy ◽  
Thermal Anisotropy ◽  
Rate Of Growth ◽  
Interplanetary Plasma ◽  
Set Up ◽  
Fire Hose

The instability of electromagnetic waves propagating across a static magnetic field in the presence of a thermal anisotropy (T∥ > T⊥) is investigated. The marginal stabifity criterion as well as the rate of growth of the instability are derived. When compared with the fire hose instability (of electromagnetic waves propagating along the static magnetic field) it is found that higher electron pressures are required for this new instability to be set up; however, the maximal rate of growth is much larger than in the fire hose case.The interplanetary plasma is stable to this thermal anisotropy instability; high β plasma devices may be unstable.The T⊥ = 0 case treated by Hamasaki is recovered.

Relaxation of a temperature anisotropy in a collisionless plasma

1970 ◽  
Vol 4 (1) ◽  
pp. 21-41 ◽  
Author(s):  
C. Montes ◽  
J. Coste ◽  
G. Diener
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Relaxation Process ◽  
Time Scales ◽  
Collisionless Plasma ◽  
Electron Plasma ◽  
Temperature Anisotropy ◽  
Quasilinear Theory ◽  
Aperiodic Instability

We study the quasifinear relaxation of an aperiodic instability, namely the instability caused by the temperature anisotropy of a collisionless electron plasma in the absence of an external magnetic field. We give a detailed description of the relaxation process and we examine the validity of the quasilinear theory (existence of separate time scales, quasilinearity of the particles' orbits).

scholarly journals Bursty emission of whistler waves in association with plasmoid collision

2017 ◽  
Vol 35 (4) ◽  
pp. 885-892 ◽  
Author(s):  
Keizo Fujimoto
Keyword(s):  
Magnetic Field ◽  
Electron Temperature ◽  
Magnetic Reconnection ◽  
High Energy ◽  
Temperature Anisotropy ◽  
Whistler Waves ◽  
High Energy Electrons ◽  
Parallel Direction ◽  
Short Time ◽  
Particle Energization

Abstract. A new mechanism to generate whistler waves in the course of collisionless magnetic reconnection is proposed. It is found that intense whistler emissions occur in association with plasmoid collisions. The key processes are strong perpendicular heating of the electrons through a secondary magnetic reconnection during plasmoid collision and the subsequent compression of the ambient magnetic field, leading to whistler instability due to the electron temperature anisotropy. The emissions have a bursty nature, completing in a short time within the ion timescales, as has often been observed in the Earth's magnetosphere. The whistler waves can accelerate the electrons in the parallel direction, contributing to the generation of high-energy electrons. The present study suggests that the bursty emission of whistler waves could be an indicator of plasmoid collisions and the associated particle energization during collisionless magnetic reconnection.

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>

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