Lunar wake at large distances


  • F. C. Michel


The expected properties of the lunar wake at large distances are examined in light of the Explorer 35 data on the solar wind interaction with the moon. It is concluded that any geomagnetic activity expected by means of the interaction of this wake with the magnetosphere would be below the limit of detectability by present methods. It is also concluded on the basis of energy conservation that the December 14–15, 1983, disturbance observed on Explorer 18 and interpreted by Ness to the wake of the moon was actually a disturbance already in the solar wind itself and not generated by the moon, although the very mild disturbance of February 11, 1964, might be attributed to the lunar wake, as was suggested by Ness. The December disturbance involved at least two orders of magnitude more disturbance energy than could be generated by a lunar source. The February disturbance is quantitatively consistent with turbulence being present in the lunar wake.