DC electric fields and solar electrons were simultaneoulsy measured by the Apollo 15 subsatellite in the earth's magnetotail at lunar orbital distance and by rocket and balloon experiments in the polar ionosphere. The magnetotail and polar ionosphere transverse electric fields are found generally to agree in magnitude and direction. The electron spectra from 0.5 to 200 keV are essentially identical, indicating that the potential difference due to parallel electric fields between the magnetotail and the rocket located in the polar ionosphere did not exceed approximately 500 V during the time of the measurements.