No abstract

An explosion-generated-plasma is explored for low and high frequency instabilities by taking into account the drift of all the plasma species together with the dust particles which are charged. The possibility of wave triplet is also discussed based on the solution of dispersion equation and synchronism conditions. High frequency instability (HFI) and low frequency instability (LFI) are found to occur in this system. LFI grows faster with the higher concentration of dust particles, whereas its growth rate goes down if the mass of the dust is higher. The ion and electron temperatures affect its growth in opposite manner and the electron temperature causes this instability to grow. In addition to the instabilities, a simple wave is also observed to propagate, whose velocity is larger for larger wave number, smaller mass of the dust and higher ion temperature.

A model of electron acceleration by an electron Bernstein mode in a parabolic density profile is developed. The mode has a Gaussian profile. It could be excited via the mode conversion of an electromagnetic wave or by an electron beam. As it attains a large amplitude, it axially traps electrons moving close to its parallel phase velocity, where parallel refers to the direction of static magnetic field. As the electrons are accelerated and tend to get out of phase with the wave, the transverse field of the mode enhances its energy and relativistic mass, increasing the dephasing length. The scheme can produce electron energies up to a few MeV.

A nonlocal theory of excitation of electron Bernstein waves in a magnetized plasma column by a gyrating relativistic electron beam has been developed. The beam response is obtained using the Vlasov equation. For a one-dimensional parabolic density profile of the background plasma, the mode structure equation yields Hermite polynomial eigenfunctions. The growth of the Bernstein wave occurs via a fast cyclotron interaction. For a typical case when the electron cyclotron frequency is comparable to the electron plasma frequency and beam velocity vb≈0.8c, the growth rate is maximum for k⊥ρ0≈5. The nonlocal effects reduce the growth rate.