scholarly journals Temperature anisotropy instabilities stimulated by the interplay of the core and halo electrons in space plasmas

2018 ◽  
Vol 25 (2) ◽  
pp. 022902 ◽  
Author(s):  
M. Lazar ◽  
S. M. Shaaban ◽  
H. Fichtner ◽  
S. Poedts
Keyword(s):  
Space Plasmas ◽  
Temperature Anisotropy ◽  
The Core

scholarly journals Whistler instabilities from the interplay of electron anisotropies in space plasmas: a quasi-linear approach

2019 ◽  
Vol 492 (3) ◽  
pp. 3529-3539 ◽  
Author(s):  
S M Shaaban ◽  
M Lazar
Keyword(s):  
Heat Flux ◽  
Free Energy ◽  
Cumulative Effects ◽  
Space Plasmas ◽  
Stable States ◽  
Temperature Anisotropy ◽  
Realistic Interpretation ◽  
Linear Approach ◽  
Statistical Studies ◽  
Equipartition Of Energy

ABSTRACT Recent statistical studies of observational data unveil relevant correlations between whistler fluctuations and the anisotropic electron populations present in space plasmas, e.g. solar wind and planetary magnetospheres. Locally, whistlers can be excited by two sources of free energy associated with anisotropic electrons, i.e. temperature anisotropies and beaming populations carrying the heat flux. However, these two sources of free energy and the resulting instabilities are usually studied independently preventing a realistic interpretation of their interplay. This paper presents the results of a parametric quasi-linear study of the whistler instability cumulatively driven by two counter-drifting electron populations and their anisotropic temperatures. By comparison to individual regimes dominated either by beaming population or by temperature anisotropy, in a transitory regime the instability becomes highly conditioned by the effects of both these two sources of free energy. Cumulative effects stimulate the instability and enhance the resulting fluctuations, which interact with electrons and stimulate their diffusion in velocity space, leading to a faster and deeper relaxation of the beaming velocity associated with a core heating in perpendicular direction and a thermalization of the beaming electrons. In particular, the relaxation of temperature anisotropy to quasi-stable states below the thresholds conditions predicted by linear theory may explain the observations showing the accumulation of these states near the isotropy and equipartition of energy.

The ion-ion acoustic instability

1987 ◽  
Vol 37 (1) ◽  
pp. 45-61 ◽  
Author(s):  
S. Peter Gary ◽  
Nojan Omidi
Keyword(s):  
Numerical Solutions ◽  
Temperature Anisotropy ◽  
Acoustic Instability ◽  
The Core ◽  
Ion Acoustic ◽  
Earth’S Bow Shock ◽  
Kinetic Instability ◽  
Electrostatic Dispersion ◽  
Effective Beam ◽  
Vlasov Plasma

This paper considers the linear theory of ion-acoustic-like instabilities in a homogeneous Vlasov plasma with two ion components, a less dense beam and a more dense core, with a relative drift velocity. Numerical solutions of the full electrostatic dispersion equation are presented, and the properties of the ion–ion acoustic instability are studied in detail. The following properties are demonstrated: (i) At relatively cold beam temperatures, the instability is fluid-like, but it becomes a beam resonant kinetic instability as the beam temperature becomes of the order of the core temperature; (ii) if the mode is unstable, its threshold lies well below the threshold of the electron–ion acoustic instability; (iii) an electron temperature anisotropy T⊥/T‖e > 1 enhances the instability and (iv) at sufficiently large beam-core relative drift speeds, electron magnetization can either detract from or enhance the instability. If field-aligned ion beams are to drive the ion-acoustic-like enhanced fluctuations observed upstream of the Earth's bow shock, the effective beam temperature must be much smaller than values quoted in the literature.

scholarly journals Solar wind temperature anisotropy constraints from streaming instabilities

2018 ◽  
Vol 613 ◽  
pp. A23 ◽  
Author(s):  
S. Vafin ◽  
M. Lazar ◽  
H. Fichtner ◽  
R. Schlickeiser ◽  
M. Drillisch
Keyword(s):  
Solar Wind ◽  
Large Deviations ◽  
The Other ◽  
Space Plasmas ◽  
Plasma Stability ◽  
Particle Collisions ◽  
Temperature Anisotropy ◽  
Large Interval ◽  
Low Rate ◽  
Kinetic Instabilities

Due to the relatively low rate of particle-particle collisions in the solar wind, kinetic instabilities (e.g., the mirror and firehose) play an important role in regulating large deviations from temperature isotropy. These instabilities operate in the high β∥ > 1 plasmas, and cannot explain the other limits of the temperature anisotropy reported by observations in the low beta β∥ < 1 regimes. However, the instability conditions are drastically modified in the presence of streaming (or counterstreaming) components, which are ubiquitous in space plasmas. These effects have been analyzed for the solar wind conditions in a large interval of heliospheric distances, 0.3–2.5 AU. It was found that proton counter-streams are much more crucial for plasma stability than electron ones. Moreover, new instability thresholds can potentially explain all observed bounds on the temperature anisotropy, and also the level of differential streaming in the solar wind.

scholarly journals Effects of the Background Turbulence on the Relaxation of Ion Temperature Anisotropy in Space Plasmas

2021 ◽  
Vol 9 ◽  
Author(s):  
Pablo S. Moya ◽  
Roberto E. Navarro
Keyword(s):  
Solar Wind ◽  
Power Law ◽  
Large Scale ◽  
Wave Spectrum ◽  
Collisionless Plasma ◽  
Space Plasmas ◽  
Ion Temperature ◽  
Temperature Anisotropy ◽  
Background Spectrum ◽  
Background Magnetic Field

Turbulence in space plasmas usually exhibits two regimes separated by a spectral break that divides the so called inertial and kinetic ranges. Large scale magnetic fluctuations are dominated by non-linear MHD wave-wave interactions following a −5/3 or −2 slope power-law spectrum. After the break, at scales in which kinetic effects take place, the magnetic spectrum follows a steeper power-law k−α shape given by a spectral index α &gt; 5/3. Despite its ubiquitousness, the possible effects of a turbulent background spectrum in the quasilinear relaxation of solar wind temperatures are usually not considered. In this work, a quasilinear kinetic theory is used to study the evolution of the proton temperatures in an initially turbulent collisionless plasma composed by cold electrons and bi-Maxwellian protons, in which electromagnetic waves propagate along a background magnetic field. Four wave spectrum shapes are compared with different levels of wave intensity. We show that a sufficient turbulent magnetic power can drive stable protons to transverse heating, resulting in an increase in the temperature anisotropy and the reduction of the parallel proton beta. Thus, stable proton velocity distribution can evolve in such a way as to develop kinetic instabilities. This may explain why the constituents of the solar wind can be observed far from thermodynamic equilibrium and near the instability thresholds.

THE LOCK-IN TRANSITION OF VORTICES IN LAYERED SUPERCONDUCTORS

1993 ◽  
Vol 07 (11) ◽  
pp. 2085-2108 ◽  
Author(s):  
D. FEINBERG ◽  
A.M. ETTOUHAMI
Keyword(s):  
Free Energy ◽  
Type Ii ◽  
Temperature Anisotropy ◽  
Layered Superconductors ◽  
Simple Interpretation ◽  
The Core ◽  
Core Energy ◽  
Field Temperature ◽  
Demagnetizing Fields ◽  
Lock In

A review of the theory of the lock-in transition of vortices onto the layer direction in type II layered superconductors is presented. This phenomenon originates from the lowering of free energy when vortex cores are centered between adjacent layers. The approaches for the low-temperature “quasi-2D" as well as the 3D anisotropic regimes are reviewed. variational method. The phenomenological model with a modulated vortex core is shown In particular, the temperature variation of the core energy modulation is obtained by a to work in all the temperature range. The behaviour of the reversible torque is described as a function of the various parameters: field, temperature, anisotropy, and the existence of the London maximum is discussed. A simple interpretation of the transition is given as well as the influence of demagnetizing fields.

scholarly journals Effects of the Background Turbulence on the Relaxation of Ion Temperature Anisotropy in Space Plasmas

2021 ◽  
Author(s):  
Pablo S Moya ◽  
Roberto E Navarro
Keyword(s):  
Solar Wind ◽  
Power Law ◽  
Large Scale ◽  
Wave Spectrum ◽  
Space Plasmas ◽  
Linear Wave ◽  
Ion Temperature ◽  
Temperature Anisotropy ◽  
Background Spectrum ◽  
Background Magnetic Field

&lt;p&gt;Turbulence in space plasmas usually exhibits two regimes separated by a spectral break that divides the so called inertial and kinetic ranges. Large scale magnetic fluctuations are dominated by MHD non-linear wave-wave interactions following a -5/3 or -3/2 slope power-law spectrum. After the break, at scales in which kinetic effects take place, the magnetic spectrum follows a steeper power-law &lt;em&gt;k&lt;sup&gt;- &amp;#945;&lt;/sup&gt;&lt;/em&gt; shape given by a spectral index &lt;em&gt;&amp;#945; &lt;/em&gt;&gt; 5/3. The location of the break and the particular value of &lt;em&gt;&amp;#945;, &lt;/em&gt;depend on plasma conditions, and different space environments can exhibit different spectral indices. Despite its ubiquitousness, the possible effects of a turbulent background spectrum in the quasilinear relaxation of solar wind temperatures are usually not considered. In this work, a quasilinear kinetic theory is used to study the evolution of the proton temperatures in a solar wind-like plasma composed by cold electrons and bi-Maxwellian protons, in which electromagnetic waves propagate along a background magnetic field. Four wave spectrum shapes are compared with different levels of wave intensity. We show that a sufficient turbulent magnetic power can drive stable protons to transverse heating, resulting in an increase in the temperature anisotropy and the reduction of the parallel proton beta. Thus, stable proton velocity distribution can evolve in such a way as to develop kinetic instabilities. This may explain why the constituents of the solar wind can be observed far from thermodynamic equilibrium and near the instability thresholds.&lt;/p&gt;

scholarly journals Limits on the core temperature anisotropy of solar wind protons

2006 ◽  
Vol 24 (7) ◽  
pp. 2057-2063 ◽  
Author(s):  
E. Marsch ◽  
L. Zhao ◽  
C.-Y. Tu
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Radial Distance ◽  
Two Dimensional ◽  
Temperature Anisotropy ◽  
The Core ◽  
Total Temperature ◽  
To Come ◽  
The Magnetic Field ◽  
Statistical Results

Abstract. We analyse the temperature anisotropy of the protons in the solar wind and thereby concentrate on plasma data obtained in the year 1976 of the Helios 1 and Helios 2 missions. We derive the core proton temperatures and , in the directions perpendicular and parallel to the magnetic field, as well as the core parallel plasma beta, . The data are separately analysed for two distance ranges, AU and AU, and divided into 24 bins for the plasma beta, in the range from to , and into 72 bins for the total temperature anisotropy, , which is here considered in the range from −0.9 to 0.9. The number of spectra in each bin is determined to obtain distributions. The statistical results are presented in two-dimensional histograms. For each column we define a critical upper and lower limit of the anisotropy. The resulting empirical points are compared with the known theoretical instability thresholds. The protons are found to come with increasing radial distance closer to the fire-hose instability threshold.

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