8,158 research outputs found
A study of Traveling Ionospheric Disturbances and Atmospheric Gravity Waves using EISCAT Svalbard Radar IPY-data
We present a statistical study of Traveling Ionospheric
Disturbances (TIDs) as observed by the EISCAT Svalbard Radar (ESR) during the
continuous IPY-run (March 2007–February 2008) with field-aligned
measurements. We have developed a semi-automatic routine for searching and
extracting Atmospheric Gravity Wave (AGW) activity. The collected data shows
that AGW-TID signatures are common in the high-latitude ionosphere especially
in the field-aligned ion velocity data (244 cases of AGW-TID signatures in
daily records), but they can be observed also in electron density (26 cases),
electron temperature (12 cases) and ion temperature (26 cases). During the
IPY campaign (in solar minimum conditions) AGW-TID events appear more
frequently during summer months than during the winter months. It remains
still as a topic for future studies whether the observed seasonal variation
is natural or caused by seasonal variation in the performance of the
observational method that we use (AGW-TID signature may be more pronounced in
a dense ionosphere). In our AGW-TID dataset the distribution of the
oscillation periods has two peaks, one around 0.5–0.7 h and the other
around 1.1–1.3 h. The diurnal occurrence rate has a deep minimum in the
region of magnetic midnight, which might be partly explained by irregular
auroral activity obscuring the TID signatures from our detection routines. As
both the period and horizontal phase speed estimates (as derived from the
classical AGW dispersion relation) show values typical both for large scale
TIDs and mesoscale TIDs it is difficult to distinguish whether the generator
for high-latitude AGW-TIDs resides typically in the troposphere or in the
near-Earth space. The results of our statistical analysis give anyway some
valuable reference information for the future efforts to learn more about the
dominating TID source mechanisms in polar cap conditions, and to improve AGW
simulations
Double bracket dissipation in kinetic theory for particles with anisotropic interactions
We derive equations of motion for the dynamics of anisotropic particles
directly from the dissipative Vlasov kinetic equations, with the dissipation
given by the double bracket approach (Double Bracket Vlasov, or DBV). The
moments of the DBV equation lead to a nonlocal form of Darcy's law for the mass
density. Next, kinetic equations for particles with anisotropic interaction are
considered and also cast into the DBV form. The moment dynamics for these
double bracket kinetic equations is expressed as Lie-Darcy continuum equations
for densities of mass and orientation. We also show how to obtain a
Smoluchowski model from a cold plasma-like moment closure of DBV. Thus, the
double bracket kinetic framework serves as a unifying method for deriving
different types of dynamics, from density--orientation to Smoluchowski
equations. Extensions for more general physical systems are also discussed.Comment: 19 pages; no figures. Submitted to Proc. Roy. Soc.
Optimization of the Wound Reparation Process
Nowadays, postoperative wound complications are quite frequent in surgery. Various medicines and physical methods are widely used to accelerate reparative regeneration (1,2). So far, the effect of oxygen air ions on the wound healing process has not been studied. Meanwhile, aeroionotherapy, characterized by an anti-oxidant action, can have an inducer effect.The purpose of the research was to study the effect of oxygen air ions on the regeneration of tissue structures of a laparotomic wound. Clinical and laboratory studies were conducted in 48 patients (divided into two groups) with acute peritonitis of appendicular origin. The patients of the basic group underwent aerorionotherapy in the early postoperative period. While using aeroionotherapy, the reparative process was faster and more perfect. The effect of oxygen air ions was accompanied by an acceleration of the inflammatory reaction course, which is manifested by the rapid migration of cellular elements to the wound surface and their differentiation into the connective tissues. This important fact explains the anti-inflammatory effect of such therapy, its capability to inhibit the alterative process and stimulate the reparative process. In the basic group, the intensity of biological consolidation was significantly different from that of the comparison group. Only 3 days after the operation, it was higher than the control value by 23.2%, after 5 days - by 37.7%, after 7 days - by 35.6% (p <0.01). Thus, the obtained data suggest that the negative oxygen air ions should have a rather pronounced regenerative effect
Interaction between superconducting vortices and Bloch wall in ferrite garnet film
Interaction between a Bloch wall in a ferrite-garnet film and a vortex in a
superconductor is analyzed in the London approximation. Equilibrium
distribution of vortices formed around the Bloch wall is calculated. The
results agree quantitatively with magneto-optical experiment where an in-plane
magnetized ferrite-garnet film placed on top of NbSe2 superconductor allows
observation of individual vortices. In particular, our model can reproduce a
counter-intuitive attraction observed between vortices and a Bloch wall having
the opposite polarity. It is explained by magnetic charges appearing due to
discontinuity of the in-plane magnetization across the wall.Comment: 4 pages, 5 figure
Spatial Solitons in Media with Delayed-Response Optical Nonlinearities
Near-soliton scanning light-beam propagation in media with both
delayed-response Kerr-type and thermal nonlinearities is analyzed. The
delayed-response part of the Kerr nonlinearity is shown to be competitive as
compared to the thermal nonlinearity, and relevant contributions to a
distortion of the soliton form and phase can be mutually compensated. This
quasi-soliton beam propagation regime keeps properties of the incli- ned
self-trapped channel.Comment: 7 pages, to be published in Europhys. Let
The impact of QCD plasma instabilities on bottom-up thermalization
QCD plasma instabilities, caused by an anisotropic momentum distributions of
the particles in the plasma, are likely to play an important role in
thermalization in heavy ion collisions. We consider plasmas with two different
components of particles, one strongly anisotropic and one isotropic or nearly
isotropic. The isotropic component does not eliminate instabilities but it
decreases their growth rates. We investigate the impact of plasma instabilities
on the first stage of the ``bottom-up'' thermalization scenario in which such a
two-component plasma emerges, and find that even in the case of non-abelian
saturation instabilities qualitatively change the bottom-up picture.Comment: 12 pages, latex, one typo corrected, several minor changes in the
abstract and the text, to appear in JHE
Equilibration in the time-dependent Hartree-Fock approach probed with the Wigner distribution function
Calculating the Wigner distribution function in the reaction plane, we are
able to probe the phase-space behavior in time-dependent Hartree-Fock during a
heavy-ion collision. We compare the Wigner distribution function with the
smoothed Husimi distribution function. Observables are defined to give a
quantitative measure for local and global equilibration. We present different
reaction scenarios by analyzing central and non-central and
collisions. It is shown that the initial phase-space
volumes of the fragments barely merge. The mean values of the observables are
conserved in fusion reactions and indicate a "memory effect" in time-dependent
Hartree-Fock. We observe strong dissipation but no evidence for complete
equilibration.Comment: 12 pages, 10 figure
Hydrodynamic Instability of the Flux-antiflux Interface in Type-II Superconductors
The macroturbulence instability observed in fluxline systems during
remagnetization of superconductors is explained. It is shown that when a region
with flux is invaded by antiflux the interface can become unstable if there is
a relative tangential flux motion. This condition occurs at the interface when
the viscosity is anisotropic, e.g., due to flux guiding by twin boundaries in
crystals. The phenomenon is similar to the instability of the tangential
discontinuity in classical hydrodynamics. The obtained results are supported by
magneto-optical observations of flux distribution on the surface of a YBCO
single crystal with twins.Comment: 12 pages, 3 figures, submitted to Physical Review Letter
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