(a) Time development of magnetic field energy of ﹩B_{y}﹩ component during the tearing stage. (b) Energy spectrum of ﹩B_{y}﹩ component on the line ﹩y=0﹩ at ﹩\omega _{pe}t=150﹩. The horizontal axis in (b) shows the wavenumber normalized by the width of the compressed current sheet ﹩L_{\mathrm{comp}\,}﹩.