Electrostatic parametric instabilities arising from relativistic electron mass oscillations

The relativistic oscillation of the electron mass in very intense high frequency fields can give rise to parametric instabilities. These instabilities, whose growth rates do not depend on the electron-to-ion mass ratio, will surpass the oscillating two-stream instability and become the dominant process when the laser beam produces electron mass variations of the order of (me/Mi)1/3 or about 6.5×10−2 for deuterium. This corresponds to oscillating energies of a few ten keV. The linear and nonlinear stages of these instabilities are investigated through analytic methods and computer simulations.