NASCAP-2K simulations of a VLF antenna in plasma

Summary form only given. The response of a plasma to very low frequency (VLF) (3 kHz to 20 kHz) antennas at orbital altitudes of 1000 to 10,000 kilometers has been a subject of scientific interest for many decades. As this antenna frequency is less than either the plasma frequency or the electron gyrofrequency (both nearly 300 kHz for a plasma density of 10⁹ m^-3 and a magnetic field of 0.1 gauss), only certain modes can propagate as an electromagnetic (EM) wave, and the near field is dominated by electrostatic (ES) effects. Although a comprehensive self-consistent EM-ES simulation is the desired goal, there are many computational challenges to be overcome, so we begin with a quasistatic simulation to sort out the dominant ES effects. We present antenna simulations using Nascap-2k, modeling the plasma using both an explicit particle in-cell (PIC) approach and a hybrid approach with PIC ions and fluid barometric electron densities. In the latter, electron plasma oscillations are suppressed, while in the former they are excited. Accuracy of the simulations is assessed by comparison with lower dimensional simulations of similar cases