Measurements of the perturbed-interplanetary magnetic field in the lunar wake

Measurements of the interplanetary magnetic field in the vicinity of the moon have been made from lunar orbit on the Explorer 35 spacecraft. No shocks are observed in the vicinity of the moon, either in front of the moon or within 5.4 RM behind the moon. The interplanetary magnetic field appears to be convected past the lunar body without much distortion. A regular pattern of magnetic perturbations is observed when passing through the lunar wake. The perturbation amplitude is small and variable, typically less than 30% of the ambient interplanetary magnetic field. Simultaneous measurements made by Explorer 33 while in the interplanetary medium but not in the lunar wake show that even sharp changes in the interplanetary magnetic field are found essentially undistorted in the lunar wake. These simultaneous measurements also help to identify the magnetic perturbation pattern in the wake region.