1,275 research outputs found
Kinetic theory of electromagnetic ion waves in relativistic plasmas
A kinetic theory for electromagnetic ion waves in a cold relativistic plasma
is derived. The kinetic equation for the broadband electromagnetic ion waves is
coupled to the slow density response via an acoustic equation driven by
ponderomotive force like term linear in the electromagnetic field amplitude.
The modulational instability growth rate is derived for an arbitrary spectrum
of waves. The monochromatic and random phase cases are studied.Comment: 7 pages, 4 figures, to appear in Physics of Plasma
Nonlinear wave interactions in quantum magnetoplasmas
Nonlinear interactions involving electrostatic upper-hybrid (UH),
ion-cyclotron (IC), lower-hybrid (LH), and Alfven waves in quantum
magnetoplasmas are considered. For this purpose, the quantum hydrodynamical
equations are used to derive the governing equations for nonlinearly coupled
UH, IC, LH, and Alfven waves. The equations are then Fourier analyzed to obtain
nonlinear dispersion relations, which admit both decay and modulational
instabilities of the UH waves at quantum scales. The growth rates of the
instabilities are presented. They can be useful in applications of our work to
diagnostics in laboratory and astrophysical settings.Comment: 15 pages, to appear in Physics of Plasma
Astrid-2, an advanced microsatellite for auroral research
International audienceThe successful launch of the Swedish microsatellite Astrid-2 in December 1998 began a new era of auroral research, with advanced microprobes of 30 kg or less used as research tools. Innovative technologies and low-mass solutions were used for the sensors and deployment systems to allow a fairly complete set of scientific instruments within the 10 kg allocated for the scientific payload. A newly developed wire boom deployment system proved to function excellently. During its seven month lifetime Astrid-2 collected more than 26 Gbytes of high-quality data of auroral electric and magnetic fields, and auroral particle and plasma characteristics from approximately 3000 orbits at an inclination of 83° and an altitude of about 1000 km. Scientific results cover a broad range of topics, from the physics of energization of auroral particles to how the magnetosphere responds to the energy input from the solar wind and global magnetic field modelling. The fulfilment of both the technological and the scientific mission objectives has opened entirely new possibilities to carry out low-budget multipoint measurements in near-Earth space
Extracellular superoxide dismutase and other superoxide dismutase isoenzymes in tissues from nine mammalian species
Magnetospheric response to the solar wind as indicated by the cross-polar potential drop and the low-latitude asymmetric disturbance field
International audienceThe cross-polar potential drop ?pc and the low-latitude asymmetric geomagnetic disturbance field, as indicated by the mid-latitude ASY-H magnetic index, are used to study the average magnetospheric response to the solar wind forcing for southward interplanetary magnetic field conditions. The state of the solar wind is monitored by the ACE spacecraft and the ionospheric convection is measured by the double probe electric field instrument on the Astrid-2 satellite. The solar wind-magnetosphere coupling is examined for 77 cases in February and from mid-May to mid-June 1999 by using the interplanetary magnetic field Bz component and the reconnection electric field. Our results show that the maximum correlation between ?pc and the reconnection electric field is obtained approximately 25 min after the solar wind has reached a distance of 11 RE from the Earth, which is the assumed average position of the magnetopause. The corresponding correlation for ASY-H shows two separate responses to the reconnection electric field, delayed by about 35 and 65 min, respectively. We suggest that the combination of the occurrence of a large magnetic storm on 18 February 1999 and the enhanced level of geomagnetic activity which peaks at Kp = 7- may explain the fast direct response of ASY-H to the solar wind at 35 min, as well as the lack of any clear secondary responses of ?pc to the driving solar wind at time delays longer than 25 min
New Quantum Limits in Plasmonic Devices
Surface plasmon polaritons (SPPs) have recently been recognized as an
important future technique for microelectronics. Such SPPs have been studied
using classical theory. However, current state-of-the-art experiments are
rapidly approaching nanoscales, and quantum effects can then become important.
Here we study the properties of quantum SPPs at the interface between an
electron quantum plasma and a dielectric material. It is shown that the effect
of quantum broadening of the transition layer is most important. In particular,
the damping of SPPs does not vanish even in the absence of collisional
dissipation, thus posing a fundamental size limit for plasmonic devices.
Consequences and applications of our results are pointed out.Comment: 5 pages, 2 figures, to appear in Europhysics Letter
Cosmic magnetic fields from velocity perturbations in the early Universe
We show, using a covariant and gauge-invariant charged multifluid
perturbation scheme, that velocity perturbations of the matter-dominated dust
Friedmann-Lemaitre-Robertson-Walker (FLRW) model can lead to the generation of
cosmic magnetic fields. Moreover, using cosmic microwave background (CMB)
constraints, it is argued that these fields can reach strengths of between
10^{-28} and 10^{-29} G at the time the dynamo mechanism sets in, making them
plausible seed field candidates.Comment: 11 pages, 1 figure, IOP style, minor changes and typos correcte
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