Initial distribution of the background plasma density fluctuations δn/n0 in the plane (x, y), corresponding to the average level ﹩{\rm{\Delta }}N=\langle {(\delta n/{n}_{0})}^{2}{\rangle }^{1/2}\simeq 0.05﹩. The size of the box is ﹩{L}_{x}\times {L}_{y}=5792\times 2896{\lambda }_{D}^{2}﹩.