摘要: In this paper, the y-component of magnetic field line curvature in the plasma sheet was analyzed, and two kinds of shear structures of the flapping current sheet were found, i.e. symmetric and antisymmetric. The alternating bending orientations of the guiding field are exactly corresponding to alternating north-south asymmetries of the bouncing ion population in the sheet center. Those alternating asymmetric plasma sources consequently induce the current sheet flapping motion as a driver. In addition, a substantial particle population with downward motion was observed in the center of a bifurcated current sheet. This population is identified as the quasi-adiabatic particles, and provides a net current opposite to the conventional cross-tail current.
摘要: Space radiation has been identified as the main health hazard to crews involved in manned Mars missions. Active shielding is more effective than passive shielding to the very energetic particles from cosmic rays. Particle motion in a magnetic field is studied based on the single-particle theory and Monte Carlo method. By comparing the shielding efficiency of different magnetic field configurations, a novel active magnetic shielding configuration with lower mass cost and power consumption is proposed for manned Mars missions. The new magnetic configuration can shield 92.8% of protons and 84.4% of alpha particles with E < 4 GeV·n-1, when considering the passive shielding contribution of 10.0 g·cm-2 Al Shielding, the required magnetic stiffness can be reduced from 27 Tm to 16 Tm. The detailed analysis of mass cost and power consumption shows that active shielding will be a promising means to protect crews from space radiation exposure in manned Mars missions.