In this project you will study what happens when an electromagnetic wave is sent into an unmagnetized plasma. It will illustrate the concepts of cutoffs, reflection, skin depths, and phase and group velocity.
You will simulate plasmas in which each plasma electron is initialized with positions (only in x, or what we call ) such that the plasma has a nonuniform density profile. In some cases, the density is zero until a specific , at which time it rises sharply to a value of . It then remains at this value until , which is the edge of the simulation window. In other cases, the density is zero until , at which time is rises to a value of between and . It then remains constant until (the edge of the simulation window).
The spacing between the electrons is proportional to the inverse of the density. Each electron is also initialized with velocities ( , , ) = ( , , ) or momentum ( , , ) from a Maxwellian in each direction. The particles then begin to move in the self-consistent fields that their current and charge density produce.
At , an electromagnetic (EM) wave polarized in the direction with a pulse duration of is launched by an antenna from the left hand boundary. The peak amplitude is . In the first example, the EM wave has a frequency of , while in the later examples it has a frequency of .