Simple linear relationships are given for the dependence of the potential drop across the polar cap on interplanetary parameters. The linear regression parameters are obtained by least-square fits to AE-C, AE-D, and S3-3 satellite data. Parameters are listed for the dependence on a variety of interplanetary parameters, including the solar wind velocity and the interplanetary magnetic field components. Variation with Kp is given by Senior et al. (1990).
References: P. H. Reiff, R. W. Spiro, and T. W. Hill, Dependence of Polar Cap Potential Drop on Interplanetary Parameters, J. Geophys. Res. 86, 7639, 1981.
C. Senior, D. Fortaine, G. Claudal, D. Alcayd_, and J. Fontanari, Convection Electric Fields and Electrostatic Potential Observed with the EISCAT Facility, Annales Geophysicae 8, 257, 1990.