Acceleration of electrons by a lower hybrid wave in a magnetic mirror

Abstract

In the present study, a theory of electron acceleration by a very large-amplitude lower hybrid wave (LHW) in a magnetic mirror having frequency less than the plasma frequency is developed. The LHW has a Gaussian mode profile and is localized due to the parabolic plasma density and the magnetic field profile. The mode can be excited by launching an electron beam from outside into the magnetic mirror. Large-amplitude LWHs have potential to axially trap the electrons when they are moving nearly parallel to the phase velocity, where parallel refers to the direction of the axial magnetic field. The energy of the electrons is enhanced at the instant of interaction between the wave and the electrons. The acceleration of electrons possibly stops as the electrons gets out of phase with the wave. The transverse field of the mode favors stronger mirror confinement and increases the dephasing length. This theory can accelerate electrons up to keV energies and can be employed in the heating of electrons in a magnetic mirror.