APPLICATION OF NON-OSCILLATORY, NON-FREE PARAMETER DIFFERENCE SCHEME ON SIMULATION OF SOLAR WIND FLOW IN A HELMET MAGNETIC STRUCTURE
YE Zhanyin WEI Fengsi WANG Chi FENG Xueshang SHI Yong YAO Jiusheng(Center for Space Science and Applied Research, The Chinese Academy of Sciences, Beijing 100080)
An algorithm called NNDMHD for the two-dimensional, three-component, eight-variable and time-dependent magnetohydrodynamic (MHD) conservative equations is proposed. It reduces Lorentz force error caused by numerical magnetic field divergence's non-zero error in a method of dividing magnetic field into two parts, a potential one invariant of time and a non-potential one varying with time. Then, NNDMHD could be developed from the Non-oscillatory, Non-free parameter Difference scheme (NND), which is very effective in numerical simulation of gas-dynamical transonic flow.At first, numerical tests on NNDMHD are carried out on a typical one-dimensional Riemann case and a two-dimensional Orszag-Tang example. The good numerical results agree with those of references and exhibit no non-physical oscillation near discontinuities. Then, example of solar wind flow in a helmet magnetic field structure being axisymmetric in meridian plane is taken for NNDMHD numerical test. In this example, although physical variables vary in a large scale (-10-4) in radial direction, NNDMHD can still reduce Lorentz force error caused by numerical magnetic field divergence's non-zero error. The numerical result in this example shows that: although the grid mesh is coarser four times than that of usual one, NNDMHD can still keep stable in computation for final steady state result.