Top: growth of individual Fourier modes for b_x (for the run labeled Fig. 4 in Table 3). The modes shown are those for i = 0,1,2, and j = 0,1,...,25, and one mode every 100 modes for the remaining. We note that the graphic has been cut and that the weak modes actually fill a continuum down to an energy of 10^-7. The sum of all 320 × 90 modes is shown in orange. We recall that mode (i,j) corresponds to (k_zd_e,k_xd_e) = 2π × 20(i/640,j/180). Bottom: growth map of the Fourier modes, in units of T_pe.