Curvilinear Particle-in-Cell Code Simulations of Plasma Sheath Effects on the Impedance of a Very Low Frequency Dipole Antenna Operating in the Inner Magnetosphere

If a high-altitude nuclear explosion (HANE) were to occur, it would produce an artificial radiationbelt in the earth's upper atmosphere that would populate the earth's magnetic field with trappedhigh-energy electrons that can severely damage or destroy nearly all lower-earth orbit (LEO)satellites in a short amount of time. Therefore, it has been of much interest over the years to devisea scheme that remediates these MeV electrons from the inner magnetosphere and reduces theamount of damage caused by them. One of the techniques is to use a space-borne high voltagedipole antenna to generate very low frequency (VLF) whistler waves along the earth's magneticfield lines to pitch angle scatter the electrons. However, due to the magnetosphere being composedof plasma, a nonlinear plasma sheath forms around the dipole, which changes the input impedanceof the antenna. Therefore, it is crucial to understand the effects the sheath has on the antennaimpedance through numerical simulation, and to use these simulations to effectively inject whistlerwaves into the magneto plasma environment for optimal particle remediation. The research usesa three-dimensional electrostatic curvilinear particle-in-cell (CPIC) code to simulate the sheathand its effects on the antenna's terminal impedance, which is then compared to existing analyticalsheath models. In addition, simulations that vary the antenna's orientation relative to the earth'smagnetic field and varying its operating frequency are also presented. LA-UR-21-26919