Intense microwave generation by the negative-mass instability

Abstract

This paper examines the negative‐mass stability properties of an E layer for transverse electric (TE) and transverse magnetic (TM) waveguide modes in a conducting cylinder. The analysis is carried out for a relativistic non‐neutral E layer aligned parallel to a uniform axial magnetic field B₀ê_z, within the context of the assumptions that the electron motion is ultrarelativistic (γ₀≫1) and that (ν/γ₀)^1/3≪1, where ν is Budker’s parameter and γ₀mc² is the electron energy. One of the most important features of the analysis is that the axial energy spread can have a large influence on the stability behavior for both the TE and TM waveguide modes. By an appropriate choice of system parameters, it is shown that the spectrum of microwave radiation generated by the negative‐mass instability can be very narrowband.