Particle-in-cell simulations on antenna characteristics in space plasma

We focused on a dipole antenna immersed in space plasma and studied the antenna characteristics, such as input impedance, effective length and pickup factor by performing 3D PIC (particle-in-cell) electromagnetic simulations. In order to include plasma kinetic effects in the analysis, we applied the PIC method to the conventional FDTD field solving simulations. In the PIC method, we solve the equation of motion for each particle with the field components obtained at grid points with the FDTD method. In the simulations, we place a receiving antenna in a 3D plasma space in such a situation that initially all electrostatic waves are propagating along the antenna length. We particularly focus on the dependence of antenna properties on the ratio between the local Debye length and the antenna length as well as the ion sheath size created around the antenna. Preliminary results are also shown on the effects of photo-electron emission on the antenna impedance. We also considered the finite size of a conducting spacecraft and examined the antenna properties by changing the ratio between the spacecraft size and the antenna length.