The Earth is rotating and has a permanent Magnetic field. It does not exhibits a correspondent Electric field. The answer is 0.
The magnetic field is due to the presence of a relative motion between the charges inside the Earth (electric dipole) and the observer. Thus, it is a derived quantity much like the Coriolis force. Instead of saying magnetic field I think more appropriate to say magnetic force.
by Hans de Vries: The simplest, and the full derivation of Magnetism as a Relativistic side efect of ElectroStatics He uses only Electrostactic field and the non-simultaneity to derive the Magnetic Field.