Time development of the magnetic field ﹩B_{x}/ B_{0}﹩ and the phase space ﹩y/ L_{0}- v_{i,z}/ v_{\mathrm{th}\,,i}﹩ plots for some ions at ﹩\omega _{pe}t=0﹩, 300, and 600. In (a.1)–(a.3), the magnetic field ﹩B_{x}/ B_{0}﹩ is plotted on the ﹩x=5L_{0}﹩ line between ﹩y/ L_{0}=0﹩ and ﹩y/ L_{0}=5﹩. Some ions whose velocities are larger than ﹩3v_{\mathrm{th}\,,i}﹩ are randomly picked up from the region between ﹩y/ L_{0}=0﹩ and ﹩y/ L_{0}=5﹩ in (b.1)–(b.3).