Subharmonic resonances in plasmas: exponential and superexponential growth of driven relativistic plasma waves
Subharmonic resonant beat-wave excitation of nonlinear relativistic plasma waves is studied analytically and in particle-in-cell simulations. We find that if the frequency separation of the lasers, Deltaomega, is 2omega(p) or 3omega(p) ( omega(p) is the plasma frequency), then plasma waves are still excited at omega(p) but they grow exponentially or superexponentially rather than secularly. Both of these subharmonic resonant instabilities saturate due to relativistic detuning. The analytical growth rates and saturation levels agree with the simulation results.
Ren
C
Department of Physics & Astronomy, University of California, Los Angeles, California 90095-1547, USA.
Dodd
ES
Gordon
D
Mori
WB