Plasma distribution functions in the Earth's magnetotail (XGSM∼ −42RE) at the time of a magnetospheric substorm: GEOTAIL/LEP observation

1994 ◽  
Vol 21 (11) ◽  
pp. 1027-1030 ◽  
Author(s):  
S. Machida ◽  
T. Mukai ◽  
Y. Saito ◽  
M. Hirahara ◽  
T. Obara ◽  
...  
Keyword(s):  
Distribution Functions ◽  
Magnetospheric Substorm ◽  
Plasma Distribution

An instrument for rapidly measuring plasma distribution functions with high resolution

1982 ◽  
Vol 2 (7) ◽  
pp. 67-70 ◽  
Author(s):  
C.W. Carlson ◽  
D.W. Curtis ◽  
G. Paschmann ◽  
W. Michel
Keyword(s):  
High Resolution ◽  
Distribution Functions ◽  
Plasma Distribution

scholarly journals The κ-cookbook: a novel generalizing approach to unify κ-like distributions for plasma particle modelling

2020 ◽  
Vol 497 (2) ◽  
pp. 1738-1756 ◽  
Author(s):  
K Scherer ◽  
E Husidic ◽  
M Lazar ◽  
H Fichtner
Keyword(s):  
Debye Length ◽  
Distribution Functions ◽  
Energy Distributions ◽  
Pickup Ions ◽  
Plasma Distribution ◽  
Special Cases ◽  
Power Law Exponent ◽  
Velocity Moments ◽  
Analytical Expressions ◽  
Generalized Distribution

ABSTRACT In the literature different so-called κ-distribution functions are discussed to fit and model the velocity (or energy) distributions of solar wind species, pickup ions, or magnetospheric particles. Here, we introduce a generalized (isotropic) κ-distribution as a ‘cookbook’, which admits as special cases, or ‘recipes’, all the other known versions of κ-models. A detailed analysis of the generalized distribution function is performed, providing general analytical expressions for the velocity moments, Debye length, and entropy, and pointing out a series of general requirements that plasma distribution functions should satisfy. From a contrasting analysis of the recipes found in the literature, we show that all of them lead to almost the same macroscopic parameters with a small standard deviation between them. However, one of these recipes called the regularized κ-distribution provides a functional alternative for macroscopic parametrization without any constraint for the power-law exponent κ.

Suprathermal plasma distribution functions with relativistic cut-offs

2019 ◽  
Vol 491 (3) ◽  
pp. 3967-3973
Author(s):  
H-J Fahr ◽  
M Heyl
Keyword(s):  
Distribution Function ◽  
Heat Transport ◽  
Distribution Functions ◽  
The Other ◽  
Pressure Reduction ◽  
Plasma Distribution ◽  
Order Of Magnitude ◽  
Low Mass ◽  
Velocity Moments ◽  
Free Plasma

ABSTRACT In typical plasma physics scenarios, when treated on kinetic levels, distribution functions with suprathermal wings are obtained. This raises the question of how the associated typical velocity moments, which are needed to arrive at magnetohydrodynamic plasma descriptions, may appear. It has become evident that the higher velocity moments in particular, for example the pressure or heat transport, which are constructed as integrations of the distribution function, contain unphysical contributions from particles with velocities greater than the velocity of light. In what follows, we discuss two possibilities to overcome this problem. One is to calculate a maximal, physically permitted, upper velocity, which can be realized in view of the underlying energization processes, and to stop the integration there. The other is to modify the distribution function relativistically so that no particles with superluminal (v ≥ c) velocities appear. On the basis of a typical collision-free plasma scenario, like the plasma in the heliosheath, we obtain the corresponding expressions for electron and proton pressures and can show that in both cases the pressures are reduced compared with their classical values; however, electrons experience a stronger reduction than protons. When calculating pressure ratios, it turns out that these are of the same order of magnitude regardless of which of the two methods is used. The electron, as the low-mass particle, undergoes the more pronounced pressure reduction. It may turn out that electrons and protons constitute about equal pressures in the heliosheath, implying that no pressure deficit need be claimed here.

scholarly journals Kinetic entropy-based measures of distribution function non-Maxwellianity: theory and simulations

2020 ◽  
Vol 86 (5) ◽  
Author(s):  
Haoming Liang ◽  
M. Hasan Barbhuiya ◽  
P. A. Cassak ◽  
O. Pezzi ◽  
S. Servidio ◽  
...  
Keyword(s):  
Distribution Function ◽  
Magnetic Reconnection ◽  
Entropy Density ◽  
Distribution Functions ◽  
Local Distribution ◽  
Particle In Cell ◽  
Maxwellian Plasma ◽  
Plasma Distribution ◽  
Maxwellian Distribution Function ◽  
Quantitative Understanding

We investigate kinetic entropy-based measures of the non-Maxwellianity of distribution functions in plasmas, i.e. entropy-based measures of the departure of a local distribution function from an associated Maxwellian distribution function with the same density, bulk flow and temperature as the local distribution. First, we consider a form previously employed by Kaufmann & Paterson (J. Geophys. Res., vol. 114, 2009, A00D04), assessing its properties and deriving equivalent forms. To provide a quantitative understanding of it, we derive analytical expressions for three common non-Maxwellian plasma distribution functions. We show that there are undesirable features of this non-Maxwellianity measure including that it can diverge in various physical limits and elucidate the reason for the divergence. We then introduce a new kinetic entropy-based non-Maxwellianity measure based on the velocity-space kinetic entropy density, which has a meaningful physical interpretation and does not diverge. We use collisionless particle-in-cell simulations of two-dimensional anti-parallel magnetic reconnection to assess the kinetic entropy-based non-Maxwellianity measures. We show that regions of non-zero non-Maxwellianity are linked to kinetic processes occurring during magnetic reconnection. We also show the simulated non-Maxwellianity agrees reasonably well with predictions for distributions resembling those calculated analytically. These results can be important for applications, as non-Maxwellianity can be used to identify regions of kinetic-scale physics or increased dissipation in plasmas.

Plasma Distribution Functions in Accretion onto Neutron Stars

1982 ◽  
Vol 4 (4) ◽  
pp. 370-371
Author(s):  
N.F. Cramer
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Plasma Temperature ◽  
Small Region ◽  
Distribution Functions ◽  
Usual Model ◽  
Physical Conditions ◽  
Polar Caps ◽  
Plasma Distribution ◽  
Field Lines

In the usual model of discrete cosmic X-ray sources, it is assumed that a massive star loses matter to a companion neutron star, either through a stellar wind, or by means of Roche lobe overflow into an accretion disk around the neutron star (Pines 1980). The irifalling matter becomes ionized and is channelled along the magnetic field lines of the neutron star, so that it is accreted onto the star in a very small region at the magnetic polar caps. The physical conditions at these points are assumed to be: magnetic field B ~ 1012 G, plasma temperature ~107-108 K, and infall plasma velocity ~ 0.3 c-0.5 c.

Spatial variation of the kappa index in the Earth’s plasma sheet: RCMI results

2021 ◽  
Author(s):  
Sina Sadeghzadeh ◽  
Jian Yang ◽  
Ameneh Mousavi
Keyword(s):  
Plasma Sheet ◽  
Time History ◽  
Distribution Functions ◽  
Kappa Distribution ◽  
Kappa Index ◽  
Energy Fluxes ◽  
Astrophysical Plasmas ◽  
Initial Plasma ◽  
Plasma Distribution ◽  
History Of

<p>Astrophysical plasmas are collisionless and correlated systems in which particles are out of thermal equilibrium and can be characterized by non-Maxwellian distribution functions. Amongst those nonthermal distribution functions, the kappa distribution has been widely used and satisfactorily modeled numerous space plasma environments such as ring current and plasma sheet. The particles spectra observed by detector measurements onboard the satellites (e.g., Time History of Events and Macroscale Interactions during Substorms (THEMIS)) indicate that the energy fluxes of plasma sheet particles can be fitted well by the kappa distribution (or combinations thereof). Besides, many empirical models have also used such distributions to estimate fluxes at different energies. Statistically, in the RCM simulations, at all times, even geomagnetically quiet conditions, the initial plasma distribution is assumed to be a kappa function with κ≈6. However, based on the flux spectra constructed by THEMIS data, the kappa index has a significant dawn-dusk asymmetry and a clear dependency on the geocentric distance (R) and the magnetic local time (MLT). Using the averaged RCMI calculated energy fluxes in the equatorial plane we intend to analyze the spatial distribution of the spectral index both for ions (κ<sub>i</sub>) and electrons (κ<sub>e</sub>) in this region and compare the simulation results with observations.</p>

scholarly journals Experimental Study of Inhomogeneous Reflex-Discharge Plasma Using Microwave Refraction Interferometry

2018 ◽  
Vol 63 (12) ◽  
pp. 1057 ◽  
Author(s):  
Yu. V. Kovtun ◽  
Y. V. Syusko ◽  
E. I. Skibenko ◽  
A. I. Skibenko
Keyword(s):  
Phase Shift ◽  
Plasma Layer ◽  
Critical Density ◽  
Horn Antenna ◽  
Optical Path Length ◽  
Distribution Functions ◽  
Microwave Beam ◽  
Plasma Distribution ◽  
Reflex Discharge ◽  
Average Plasma Density

The phase shift at the plasma interferometry with oblique microwaves and microwaves passing through the center of a plasma formation has been calculated. The critical density Ncr and the critical radius rcr of a plasma layer, at which microwaves do not hit the horn antenna, are calculated for various radial plasma distribution functions. The time dependences of the phase shift for the transverse and oblique probing modes are experimentally measured. Using the phase shifts determined by the both methods, the time dependence of the product NpL of the electron concentration in plasma and the optical path length of a microwave beam in vacuum is found, and the average plasma density is estimated.

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