The variations of (a) the spacecraft potential, (b) the P parameter, and (c) the electron density along the SKR longitude. Three spacecraft potential profiles represent the cases of zero dust current (dotted line), 8 km s-1 spacecraft speed (solid line), and 16 kms−1 speed (dash line). All profiles fluctuate along the SKR longitude due to the electron density modulation. Compared to the case with no dust current, the spacecraft potential is shifted positively. The faster the spacecraft speed, the less negative the potential becomes.