1,018 research outputs found
Plasma wave mediated electron pairing effects
Pairing of particles, in particular electrons, in high temperature plasma is
generally not expected to occur. Here we investigate, based on earlier work,
the possibility for electron pairing mediated in the presence of various kinds
of plasma waves. We confirm the possibility for pairing in ion- and
electron-acoustic waves, pointing out the importance of the former and the
expected consequences. While electron-acoustic waves probably do not play any
role, ion-acoustic waves may cause formation of heavy electron compounds. Lower
hybrid waves also mediate pairing but under different conditions. Buneman modes
which evolve from strong currents may cause pairing among trapped electrons
constituting a heavy electron component that populates electron holes. All
pairing processes are found to generate cold pair populations. They provide a
mechanism of electron cooling which can be interpreted as kind of classical
condensation, in some cases possibly accompanied by formation of current
filaments, weak soft-X-ray emission and superfluidity which might affect
reconnection physics.Comment: Ready for submission, Journal not yet specified. 10 pages, 2 figure
Incomplete-exclusion Statistical Mechanics in Non-collisional Violent Relaxation of Celestial Objects
Violent relaxation has been proposed half a century ago to bear
responsibility for non-collisional dynamics and formation of gravitationally
bound systems of extended celestial objects (agglomeration of stars, galaxies,
clusters of galaxies) when reaching an approximate equilibrium state which can
be described thermodynamically. The Lynden-Bell equilibrium distribution of
such systems, resulting from a spatial exclusion principle, had been shown to
be an analog to the Fermi distribution of states in solid state physics. Real
extended objects like galaxies do not completely exclude each other, however.
Permitting for partial exclusion leads to a modification of the equilibrium
distribution. Here we show that this case can be treated in analogy to a
hypothetical incomplete population of Fermi states. An incomplete-exclusion
equilibrium distribution is obtained which enters the violent relaxation
theory.Comment: 17 pages, no figure
Fractional Laplace Transforms - A Perspective
A form of the Laplace transform is reviewed as a paradigm for an entire class
of fractional functional transforms. Various of its properties are discussed.
Such transformations should be useful in application to differential/integral
equations or problems in non-extensive statistical mechanics.Comment: 5 pages, no figures, to appear in Frontiers in Physics 201
Beyond Gibbs-Boltzmann-Shannon: General Entropies -- The Gibbs-Lorentzian Example
We propose a generalisation of Gibbs' statistical mechanics into the domain
of non-negligible phase space correlations. Derived are the probability
distribution and entropy as a generalised ensemble average, replacing
Gibbs-Boltzmann-Shannon's entropy definition enabling construction of new forms
of statistical mechanics. The general entropy may also be of importance in
information theory and data analysis. Application to generalised Lorentzian
phase space elements yields the Gibbs-Lorentzian power law probability
distribution and statistical mechanics. Details can be found in arXiv:1406.6639Comment: 6 pages, no figures, paper appeared in slightly different form in.
For details on application see arXiv:1406.663
Collisionless Magnetic Reconnection in Space Plasmas
Magnetic reconnection requires the violation of the frozen-in condition which
ties gyrating charged particles to the magnetic field inhibiting diffusion.
Ongoing reconnection has been identified in near-Earth space as being
responsible for the excitation of substorms, magnetic storms, generation of
field aligned currents and their consequences, the wealth of auroral phenomena.
Its theoretical understanding is now on the verge of being completed.
Reconnection takes place in thin current sheets. Analytical concepts proceeded
gradually down to the microscopic scale, the scale of the electron skin depth
or inertial length, recognizing that current layers that thin do preferentially
undergo spontaneous reconnection. Thick current layers start reconnecting when
being forced by plasma inflow to thin. For almost half a century the physical
mechanism of reconnection has remained a mystery. Spacecraft in situ
observations in combination with sophisticated numerical simulations in two and
three dimensions recently clarified the mist, finding that reconnection
produces a specific structure of the current layer inside the electron inertial
(also called electron diffusion) region around the reconnection site, the X
line. Onset of reconnection is attributed to pseudo-viscous contributions of
the electron pressure tensor aided by electron inertia and drag, creating a
complicated structured electron current sheet, electric fields, and an electron
exhaust extended along the current layer. We review the general background
theory and recent developments in numerical simulation on collisionless
reconnection. It is impossible to cover the entire field of reconnection in a
short space-limited review. The presentation necessarily remains cursory,
determined by our taste, preferences, and knowledge. Only a small amount of
observations is included in order to support the few selected numerical
simulations.Comment: Review pape
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