68 research outputs found
Instabilities for a relativistic electron beam interacting with a laser irradiated plasma
The effects of a radiation field (RF) on the unstable modes developed in
relativistic electron beam--plasma interaction are investigated assuming that
, where is the frequency of the RF and
is the plasma frequency. These unstable modes are parametrically
coupled to each other due to the RF and are a mix between two--stream and
parametric instabilities. The dispersion equations are derived by the
linearization of the kinetic equations for a beam--plasma system as well as the
Maxwell equations. In order to highlight the effect of the radiation field we
present a comparison of our analytical and numerical results obtained for
nonzero RF with those for vanishing RF. Assuming that the drift velocity
of the beam is parallel to the wave vector of the
excitations two particular transversal and parallel configurations of the
polarization vector of the RF with respect to are
considered in detail. It is shown that in both geometries resonant and
nonresonant couplings between different modes are possible. The largest growth
rates are expected at the transversal configuration when is
perpendicular to . In this case it is demonstrated that in general
the spectrum of the unstable modes in -- plane is split into two
distinct domains with long and short wavelengths, where the unstable modes are
mainly sensitive to the beam or the RF parameters, respectively. In parallel
configuration, , and at short wavelengths
the growth rates of the unstable modes are sensitive to both beam and RF
parameters remaining insensitive to the RF at long wavelengths.Comment: 23 pages, 5 figure
On the Possibility of Development of the Explosion Instability in a Two-Component Gravitating System
We obtain an expression for the energy of the density wave propagating in a
multicomponent gravitating medium in the form well known from electrodynamics.
Using the above, the possibility of "triple production" of the quasi-particles,
or waves, with their energies summing up to zero, in a non-equilibrium medium
is demonstrated. That kind of resonance wave interaction is shown to result in
the development of an explosion instability. By the method developed in plasma
physics, the characteristic time of the instability is evaluated.Comment: 15 pages, 3 figures, accepted for publication (JETP
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