1,326 research outputs found
Are perytons signatures of ball lightning?
The enigmatic downchirped signals, called "perytons", that are detected by
radio telescopes in the GHz frequency range may be produced by an atmospheric
phenomenon known as ball lightning (BL). If BLs act as nonstationary
radiofrequency cavities, their characteristic emission frequencies and
evolution time scales are consistent with peryton observations, and so are
general patterns in which BLs are known to occur. Based on this evidence,
testable predictions are made that can confirm or rule out a causal connection
between perytons and BLs. In either case, how perytons are searched for in
observational data may warrant reconsideration, for existing procedures may be
discarding events that has the same nature as known perytons
Particle Orbits in a Force-Balanced, Wave-Driven, Rotating Torus
The wave-driven rotating torus (WDRT) is a recently proposed fusion concept
where the rotational transform is provided by the E x B drift resulting from a
minor radial electric field. This field can be produced, for instance, by the
RF-wave-mediated extraction of fusion-born alpha particles. In this paper, we
discuss how macroscopic force balance, i.e. balance of the thermal hoop force,
can be achieved in such a device. We show that this requires the inclusion of a
small plasma current and vertical magnetic field, and identify the desirable
reactor regime through free energy considerations. We then analyze particle
orbits in this desirable regime, identifying velocity-space anisotropies in
trapped (banana) orbits, resulting from the cancellation of rotational
transforms due to the radial electric and poloidal magnetic fields. The
potential neoclassical effects of these orbits on the perpendicular
conductivity, current drive, and transport are discussed.Comment: 13 pages, 7 figure
Adiabatic nonlinear waves with trapped particles: III. Wave dynamics
The evolution of adiabatic waves with autoresonant trapped particles is
described within the Lagrangian model developed in Paper I, under the
assumption that the action distribution of these particles is conserved, and,
in particular, that their number within each wavelength is a fixed independent
parameter of the problem. One-dimensional nonlinear Langmuir waves with deeply
trapped electrons are addressed as a paradigmatic example. For a stationary
wave, tunneling into overcritical plasma is explained from the standpoint of
the action conservation theorem. For a nonstationary wave, qualitatively
different regimes are realized depending on the initial parameter , which is
the ratio of the energy flux carried by trapped particles to that carried by
passing particles. At , a wave is stable and exhibits group velocity
splitting. At , the trapped-particle modulational instability (TPMI)
develops, in contrast with the existing theories of the TPMI yet in agreement
with the general sideband instability theory. Remarkably, these effects are not
captured by the nonlinear Schr\"odinger equation, which is traditionally
considered as a universal model of wave self-action but misses the
trapped-particle oscillation-center inertia.Comment: submitted together with Papers I and I
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