Transient Lunar Events: Possible Causes

IN a recent communication¹, E. J. Flamm and R. E. Lingenfelter discussed the nature of luminescence and of lunar bright spots. They found that of nineteen reported bright spots in the region of Aristarchus, most occurred during years when the sunspot numbers were low, and they stated: ``Clearly the 19 events are negatively correlated with solar activity''. The Moon possesses only a negligible magnetic field and the particle flux at the Moon is, as pointed out by Flamm and Lingenfelter, too small by orders of magnitude to excite fluorescence, no matter whether flares, the solar wind, or cosmic-ray flux is invoked. A `negative' correlation with sunspot number, if interpreted as a negative (or inverse) correlation with solar activity generally, implies a connexion with magnetic phenomena just as surely as a positive or direct correlation and would be just as hard to explain.