Slice at y=0 for the times t=442 s (top row), t=489.3 s (middle row), and t=532.8 s (bottom row), showing the formation and evolution of the rain blob. Left: Density of charges. The red arrows show the in-plane velocity of charges. Right: Density of neutrals. The red arrows show the in-plane velocity of neutrals. The in-plane magnetic field lines are overplotted by blue lines in all the panels. The perturbed null point is shown by a red dot, the other null point being outside the domain plotted in these panels. At the time t=489.3 s, when the blob is formed fully (middle row), the point with a high density, situated at x=−1.25 Mm and z=0.6 Mm, is marked in the charges and neutral density panels by a blue and green dot, respectively. This point is the same point marked in Figure 4 and Figure 6 below for the panels on the second row, for a better visualization. The line along the cut used in Figure 8 below is indicated by a dashed line: blue in the charge density panel and green in the neutral density panel.