Abstract
Numerical simulations of electromagnetic interaction between the solar wind and the moderately-sized magnetic sails are made to clarify the characteristics of reaction forces exerted on the magnetic sail when its characteristic scale is reduced below the continuum limit at which the magneto-hydrodynamic approximations of the plasma flow fail. The hybrid particle-in-cell (PIC) method is used to take into account the finite Larmor-radius effect of the electromagnetic interaction between the plasma flow and the magnetic field. The magnetic dipole intensity is changed so that the characteristic size of the magnetic sail changes from several kilometers to few thousand kilometers. The results show that the drag coefficient of the magnetic sail based on the representative radius of the magneto-hydrodynamic interaction decreases as the ratio of the ion Larmor radius to this representative radius becomes greater than unity. An approximate formula to estimate the drag coefficient in a wide range of magnetic sail dimension is presented.
