Scientists' test results show that when the earth is struck by lightning, most of the negative charges in the thundercloud are discharged from Lei Yun to the earth, and a few are positive charges on the Lei Yun. In many lightning strikes in Lei Yun, the last lightning strike is often the positive charge on the Lei Yun discharging to the earth. From the observation, it is found that the lightning stroke of positive charge discharging to the earth is particularly fierce.

This proves that in most cases, the lower part of Lei Yun is negatively charged and the upper part is positively charged. The positive and negative charges carried in the thundercloud are the same, but the lower part is close to the ground, so the negative charges are easily neutralized by the discharge with the ground, and the positive charges on the upper part will accumulate more and more, and finally the discharge with the ground will be fierce.

Because most of the Lei Yun on the earth moves eastward, the direction of the magnetic field lines outside the earth is from the North Pole to the South Pole. According to the right-hand rule, the current generated by Lei Yun cutting the earth's magnetic field lines is upward, so the upper part is positively charged and the lower part is negatively charged. If the thundercloud moves westward, the charge distribution is opposite; When Lei Yun moves upward, the west of Lei Yun is positively charged and the east is negatively charged; When Lei Yun moves downward, the charge distribution is opposite.