New Mechanisms of Ion Energization by Multiple Electrostatic Waves in a Magnetized Plasma

It is shown that with two or more electrostatic waves propagating across a uniform and steady-state magnetic field, ions with arbitrarily low initial energies can be nonlinearly accelerated to very high energies. This acceleration of ions requires an appropriate choice of wave amplitudes, frequencies, and wavenumbers. The new nonlinear energization mechanism is analyzed and shown to involve both coherent and chaotic dynamics in a new way. PACS numbers: 52.40.Db, 52.20.Dq,05.45.+b The interaction between electrostatic waves and charged particles in a magnetized plasma plays a fundamental role in laboratory, space, and astrophysical plasmas. The dynamics of particles in the presence of these waves is generally nonlinear, and this wave-particle interaction is a paradigm for nonlinear Hamiltonian dynamics. The waves in the plasma can be internally generated, due to an instability, or excited by coupling to.an external source. In the test particle approach to the study of nonlinear particle dynamics, the plasma particles interacting with the waves are assumed to be a small fraction of the total population and, thus, they can be assumed to have no effect on the propagation characteristics of the waves. Consequently, in such wave-particle interactions the wave properties, once prescribed, remain the same. The interaction of ions in a magnetized plasma with a single, plane electrostatic wave, in the lower-hybrid frequency range (above the ion cyclotron frequency), and propagating across the ambient magneti