Two-dimensional fully kinetic particle-in-cell simulations of an electrodeless plasma thruster, which uses a magnetic nozzle, were conducted to investigate the thrust generation induced by the internal plasma current. The results clearly show that the E Â B and diamagnetic current densities are the major components of the internal plasma current. The simulated pressure structures reproduced the experimentally observed structures well. The results for various magnetic field strengths reveal that the E Â B effect decreases, and the diamagnetic effect becomes dominant with an increase in the magnetic field strength; this demonstrates the significant contribution of the diamagnetic effect in thrust generation.
Fully kinetic simulations of magnetic nozzle acceleration were conducted to investigate the axial momentum gains of ions and electrons with electrostatic and Lorentz forces. The axial momentum gains per ion and electron are directly calculated from the kinetics of charged particles, indicating that electrons in the magnetic nozzle obtain the net axial momentum by the Lorentz force, even though they are decelerated by the electrostatic force. Whereas ions are also accelerated by the electrostatic force, the axial momentum gain of electrons increases significantly with increasing magnetic field strength and becomes dominant in the magnetic nozzle. In addition, it is clearly shown that the axial momentum gain of electrons is due to the electron momentum conversion from the radial to the axial direction, resulting in a significant increase in the thrust and exhaust velocity.
The density profile transition and high-energy electron transport in a magnetically expanding radio frequency (RF) plasma were investigated using particle-in-cell and Monte Carlo collision techniques, where both the plasma source and the diffusion region were simulated self-consistently. The simulation results show that the density profile changes from center-peaked to bimodal plasma with increasing magnetic field strength, where bimodal plasma was observed in previous experiments. Then, the density profile transition is discussed with respect to ionization, electron temperature, and high-energy electron density. This indicates that electrons were heated by the RF field and transported radially inward across magnetic field lines. The moving distance of high-energy electrons is explained by an electron-neutral elastic collision. Therefore, the density formation depends on where the electrons are heated and how far the high-energy electrons are transported by an elastic collision, implying the longer existing time of high-energy electrons that move radially inward away from the RF antenna.
We propose radiation shielding using Martian magnetic anomalies to protect human crews on the Martian surface. We have simulated the trajectories of energetic protons using the Buneman-Boris method to measure how magnetic anomalies affect the impact rate on the Martian surface. Protons from the west can be completely eliminated, while those from the east are concentrated on the area between the magnetic poles. This would mean crews would need to concern themselves about radiation from the vertex and east only. A Martian magnetic anomaly can therefore be used to realize continuous and efficient radiation shielding.
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