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Energetic ion or electron beams cause plasma instabilities. Depending on plasma and the beam parameters, an ion beam leads to change in the dispersion relation of Alfven waves on interacting with magnetoplasmas as it can efficiently transfer its energy to the plasma. We have derived dispersion relation and the growth rates for oblique shear Alfven wave in hydrogen plasma. The particles of the beam interact with the Shear Alfven waves only when they counter-propagate each other and destabilize left-hand polarized mode for parallel waves and left-hand as well as right-hand polarized modes for oblique waves, via fast cyclotron interaction. The collisions between beam ions and plasma components affect the growth rate and the frequency of generated Alfven waves, differently for right-hand (RH) and left-hand (LH) polarized oblique Alfven modes. For (ω + kzvbo > ωbc), the most unstable mode is the LH polarized oblique Alfven mode, and it is the RH polarized oblique Alfven mode for (ω + kzvbo < ωbc), which shows a polarization reversal after resonance condition. Numerical results indicate that the growth rates increase with increase in angle of propagation. The maximum growth rate values in the presence or absence of beam increase due to obliquity of wave. [ABSTRACT FROM AUTHOR]

An electron beam propagating through a magnetized dusty plasma drives electrostatic lower hybrid waves to instability via Cerenkov interaction. A dispersion relation and the growth rate of the instability for this process have been derived taking into account the dust charge fluctuations. The frequency and the growth rate of the unstable wave increase with the relative density of negatively charged dust grains. Moreover, the growth rate of the instability increases with beam density and scales as the one-third power of the beam density. In addition, the dependence of the growth rate on the beam velocity is also discussed. [ABSTRACT FROM AUTHOR]

A density modulated electron beam propagating through a conductor-dusty plasma interface drives electromagnetic surface plasma waves (SPWs) to instability via Cerenkov and cyclotron interaction. The SPWs propagate across an external magnetic field parallel to the interface. Numerical calculations of the growth rate and unstable mode frequencies have been carried out for the typical parameters of the SPWs. The frequency and the growth rate of the unstable wave instability increase with the relative density of negatively charged dust grains δ (= nio/neo, where nio is the ion plasma density and neo is the electron plasma density). The phase velocity of the unstable waves also increases with δ. In addition, the growth rate of the instability increases with the beam density and scales as one-third power of the beam density in Cerenkov interaction and square root of beam density in fast cyclotron interaction. Moreover, the dispersion relation of SPWs has been retrieved in the absence of the modulated beam and without dust grains. [ABSTRACT FROM AUTHOR]

A density-modulated electron beam propagating through a plasma cylinder excites surface plasma waves (SPWs) via Cerenkov and fast cyclotron interaction. A nonlocal theory of this process has been developed. Numerical calculations of the growth rate and unstable mode frequencies have been carried out for the typical parameters of the SPWs. The growth rate γ (in rad/s) of the unstable wave instability increases with the modulation index Δ and has the largest value for Δ∼1 in addition to when the frequency and wave number of the modulation are comparable to that of the unstable wave. For Δ=0, γ turns out to be ∼6.06×109 rad/s for Cerenkov interaction and ∼5.47×109 rad/s for fast cyclotron interaction. The growth rate of the instability increases with the beam density and scales as one-third power of the beam density in Cerenkov interaction and is proportional to the square root of beam density in fast cyclotron interaction. The real part of the frequency of the unstable wave increases as almost the square root of the beam voltage. The results of the theory are applied to explain some of the experimental observations. [ABSTRACT FROM AUTHOR]

A density modulated electron beam propagating through a vacuum magnetized plasma interface drives electromagnetic surface plasma waves (SPWs) to instability via Cerenkov and fast cyclotron interaction. Numerical calculations of the growth rate and unstable mode frequencies have been carried out for the typical parameters of the SPWs. The growth rate γ of the unstable wave instability increases with the modulation index (Δ) and is maximized for Δ=1. For Δ=0, γ turns out to be ∼4.32×1010 rad/s for Cerenkov interaction and ∼6.81×1010 rad/s for fast cyclotron interaction. The growth rate of the instability increases with the beam density and scales as one-third power of the beam density in Cerenkov interaction and is proportional to the square root of beam density in fast cyclotron interaction. In addition, the real frequency of the unstable wave increases with the beam-energy and scales as almost one-half power of the beam-energy. [ABSTRACT FROM AUTHOR]