(a) Contour of mode (﹩{k}_{x},{k}_{y},{k}_{z}=4,0,0﹩) from spatial–temporal FFT results of B_z (the injected Alfvén wave), as well as the theoretical dispersion relations of fast (blue), Alfvén (red), and slow (black) waves. Note that fast wave and Alfvén wave are degenerate in this situation. (b) Contour of mode (﹩{k}_{x},{k}_{y},{k}_{z}=5,0,0﹩) from spatial–temporal FFT results of ﹩\delta \rho ﹩, as well as the theoretical dispersion relations of fast (blue), Alfvén (red), and slow (black) waves. (c) Contour of mode (﹩{k}_{x},{k}_{y},{k}_{z}=5,1,2﹩) from spatial–temporal FFT results of ﹩\delta \rho ﹩, as well as the theoretical dispersion relations of fast (blue), Alfvén (red), and slow (black) waves. Analyses uses the simulation data from t = 2 and 2.4, ﹩\beta =0.5﹩, and ﹩\delta B=0.2.﹩