1,857 research outputs found
Growth rates of the Weibel and tearing mode instabilities in a relativistic pair plasma
We present an algorithm for solving the linear dispersion relation in an
inhomogeneous, magnetised, relativistic plasma. The method is a generalisation
of a previously reported algorithm that was limited to the homogeneous case.
The extension involves projecting the spatial dependence of the perturbations
onto a set of basis functions that satisfy the boundary conditions (spectral
Galerkin method). To test this algorithm in the homogeneous case, we derive an
analytical expression for the growth rate of the Weibel instability for a
relativistic Maxwellian distribution and compare it with the numerical results.
In the inhomogeneous case, we present solutions of the dispersion relation for
the relativistic tearing mode, making no assumption about the thickness of the
current sheet, and check the numerical method against the analytical
expression.Comment: Accepted by PPC
The exact Darwin Lagrangian
Darwin (1920) noted that when radiation can be neglected it should be
possible to eliminate the radiation degrees-of-freedom from the action of
classical electrodynamics and keep the discrete particle degrees-of-freedom
only. Darwin derived his well known Lagrangian by series expansion in
keeping terms up to order . Since radiation is due to acceleration the
assumption of low speed should not be necessary. A Lagrangian is suggested that
neglects radiation without assuming low speed. It cures deficiencies of the
Darwin Lagrangian in the ultra-relativistic regime.Comment: 2.5 pages, no figure
Classical dilute relativistic plasma in equilibrium. Two-particle distribution function
We consider here a dilute hot plasma which is homogeneous and in equilibrium in the framework of classical relativistic statistical mechanics as formulated recently by the authors. No external fields are present. The two-particle distribution function of the plasma is calculated for any temperature. This distribution will be physically significant, as long as the creation of pairs can be neglected. Several limits which apply at low or high temperatures are discussed. Comparison with previous work from several authors is made
Status of the NICA project at JINR
AbstractThe NICA (Nuclotron-based Ion Collider fAcility) project is now under active realization at the Joint Institute for Nuclear Research (JINR, Dubna). The main goal of the project is a study of hot and dense strongly interacting matter in heavy ion (up to Au) collisions at the centre-of-mass energies up to 11 GeV per nucleon. Two modes of operation are foreseen, collider mode and extracted beams, with two detectors: MPD and BM@N. The both experiments are in preparation stage. An average luminosity in the collider mode is expected as 10E27 cm-2 s-1 for Au (79+). Extracted beams of various nucleus species with maximum momenta of 13 GeV/c (for protons) will be available. A study of spin physics with extracted and colliding beams of polarized deuterons and protons at the energies up to 27 GeV (for protons) is foreseen with the NICA facility. The proposed program allows one to search for possible signs of phase transitions and critical phenomena as well as to shed light on the problem of thenucleon spin structure
Agrogeosystems of Krasnoyarsk krai: natural resource potential, environmental stability, optimization of functioning
The article presents the estimation of natural resource potential (NRP) of agrogeosystems of taiga-forest and forest-steppe zones, environmental stability and anthropogenic transformation to further optimization of their functionin
Magnetic Field Limitations on Advection Dominated Flows
Recent papers discussing advection dominated accretion flows (ADAF) as a
solution for astrophysical accretion problems should be treated with some
caution because of their uncertain physical basis. The suggestions underlying
ADAF involve ignoring the magnetic field reconnection in heating of the plasma
flow, assuming electron heating due only to binary Coulomb collisions with
ions. Here, we analyze the physical processes in optically thin accretion flows
at low accretion rates including the influence of an equipartition turbulent
magnetic field. For these conditions there is continuous destruction of
magnetic flux by reconnection.
The reconnection is expected to significantly heat the electrons which can
efficiently emit magnetobremstrahlung radiation. Because of this electron
emission, the radiative efficiency of the ADAF is not small. We suggest that
the small luminosities of nearby galactic black holes is due to outflows rather
than ADAF accretion.Comment: 7 pages, 3 figures, Submitted to Ap
Blue spectra and induced formation of primordial black holes
We investigate the statistical properties of primordial black hole (PBH)
formation in the very early Universe. We show that the high level of
inhomogeneity of the early Universe leads to the formation of the first
generation PBHs. %The existence of these PBHs This causes later the appearance
of a dust-like phase of the cosmological expansion. We discuss here a new
mechanism for the second generation of PBH formation during the dust-like
phase. This mechanism is based on the coagulation process. We demonstrate that
the blue power spectrum of initial adiabatic perturbations after inflation
leads to overproduction of primordial black holes with gg if the power index is .Comment: 16 pages, 2 figure
Submillimeter and X-ray observations of an X Class flare
The GOES X1.5 class flare that occurred on August 30,2002 at 1327:30 UT is
one of the few events detected so far at submillimeter wavelengths. We present
a detailed analysis of this flare combining radio observations from 1.5 to 212
GHz (an upper limit of the flux is also provided at 405 GHz) and X-ray.
Although the observations of radio emission up to 212 GHz indicates that
relativistic electrons with energies of a few MeV were accelerated, no
significant hard X-ray emission was detected by RHESSI above ~ 250 keV. Images
at 12--20 and 50--100 keV reveal a very compact, but resolved, source of about
~ 10" x 10". EUV TRACE images show a multi-kernel structure suggesting a
complex (multipolar) magnetic topology. During the peak time the radio spectrum
shows an extended flatness from ~ 7 to 35 GHz. Modeling the optically thin part
of the radio spectrum as gyrosynchrotron emission we obtained the electron
spectrum (spectral index delta, instantaneous number of emitting electrons). It
is shown that in order to keep the expected X-ray emission from the same
emitting electrons below the RHESSI background at 250 keV, a magnetic field
above 500 G is necessary. On the other hand, the electron spectrum deduced from
radio observations >= 50 GHz is harder than that deduced from ~ 70 - 250 keV
X-ray data, meaning that there must exist a breaking energy around a few
hundred keV. During the decay of the impulsive phase, a hardening of the X-ray
spectrum is observed which is interpreted as a hardening of the electron
distribution spectrum produced by the diffusion due to Coulomb collisions of
the trapped electrons in a medium with an electron density of n_e ~ 3E10 - 5E10
cm-3.Comment: Accpeted in Astronomy & Astrophysics. 9 Pages, 6 Figures ADDED
REFERENCE
Циркадианные изменения микрореологических свойств крови у больных хроническим бронхитом
Studies of circadian rhythmicity blood microrheological parameters (erythrocytes deformability and agregability) and relative plasma viscosity in COPD patients with different degree of respiratory insuffisiency and healthy subjects have been carried out. The presence of distinctive circadian rhythmicity of noted values changes both in patients and healthy subjects was determined. Microrheological values biological rhythm disorders creating critical situation for microcirculation at night and early morning hours in COPD patients grew progressively worse while intensifiing of respiratory insufficiency clinical manifestation.Проводили исследования циркадных ритмов (ЦР) микрореологических параметров крови (агрегантной способности и формы эритроцитов) у больных хроническим обструктивным бронхитом с различной степенью дыхательной недостаточности (ДН). Такие же исследования выполнили в группе здоровых лиц. Выявили наличие четких ЦР вышеозначенных параметров в обеих группах. По мере усиления ДН у больных хроническим обструктивным бронхитом увеличивались и выраженные расстройства микроциркуляции в ночные и ранние утренние часы
Numerical solution of the linear dispersion relation in a relativistic pair plasma
We describe an algorithm that computes the linear dispersion relation of
waves and instabilities in relativistic plasmas within a Vlasov-Maxwell
description. The method used is fully relativistic and involves explicit
integration of particle orbits along the unperturbed equilibrium trajectories.
We check the algorithm against the dispersion curves for a single component
magnetised plasma and for an unmagnetised plasma with counter-streaming
components in the non-relativistic case. New results on the growth rate of the
Weibel or two-stream instability in a hot unmagnetised pair plasma consisting
of two counter-streaming relativistic Maxwellians are presented. These are
relevant to the physics of the relativistic plasmas found in gamma-ray bursts,
relativistic jets and pulsar winds.Comment: Accepted by Plasma Physics and Controlled Fusio
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