Increasing the peaks of non‐linear electron density near critical density in terahertz–plasma interaction

Increasing the peaks of non‐linear electron density in the interaction between high‐power terahertz beams and plasmas with electron density and electron temperature ramps is investigated. Considering the linear inhomogeneities and using the non‐linear electron density, a non‐linear differential equation governing the wave propagation is derived. Results show that the slope of the temperature and density ramps and their signs affect the amplitude and wavelength of oscillations of electric and magnetic fields. These effects are a result of the ponderomotive non‐linearity that changes the distribution of plasma density and leads to the modification of electric and magnetic fields. Furthermore, increase or decrease in the electric field amplitude is because of the energy exchange between electrons and electric field. Profiles of the non‐linear electron density indicate that, for positive values of temperature ramp, the amplitude of non‐linear electron density decreases, and the wavelength of oscillations increases. However, for negative values of temperature ramp, this behaviour is vice versa. It is also illustrated that, close to critical density, electrons become more steepened. Finally, it is concluded that both positive values of density ramp and negative values of temperature ramp increase the peaks of non‐linear electron density, especially near the critical density.