Solar wind particles reflected by the lunar magnetic field are major energy source of electromagnetic wave activities around the moon. In addition to known waves such as 100 s magnetohydrodynamic waves and 1 Hz whistler mode waves generated by protons, or non-monochromatic whistler mode waves generated by mirror-reflected electron beams, Kaguya found a new type of whistler mode waves at an altitude of 100 km above the polar regions of the moon, not above intense magnetic anomalies. The frequency range 1-16 Hz was broad like the non-monochromatic waves generated by electron beams, but their occurrence was less sensitive to the magnetic connection like the waves generated by reflected protons. They appear diffuse both in time and frequency domains, and the polarization was right-handed with respect to the background magnetic field. The wave number vector was nearly parallel to the background magnetic field which was perpendicular to the solar wind flow. The diffuse waves are thought to be generated by solar wind ions reflected by the lunar magnetic field through cyclotron resonance. The resonant ions were expected to have velocity component parallel to the magnetic field larger than the solar wind bulk speed, but such ions were not always detected simultaneously. There is a possibility that the waves were generated above the dayside moon and then propagated along the magnetic field convected by the solar wind to reach polar regions to be detected by Kaguya.

Reversal of unified polarization of low-frequency magnetic field variation was found by Kaguya at equator crossings in the lunar wake under the condition of dawn-dusk directed background magnetic field. The polarization was left-handed over a frequency range from 0.01 to 0.3 Hz in the southern hemisphere of the lunar wake in the dawnward-directed magnetic field. It turned to be right-handed when the spacecraft entered the northern hemisphere of the wake. In the duskward-directed magnetic field the polarization reversed. The same configuration by 90 degrees rotated was observed in northward-directed magnetic field, too. The sense of rotation was alike that of surface waves generated by Kelvin-Helmhlotz instability, but it was not likely because the waves of unified polarization were not always accompanied by velocity shear. They penetrated into the very center of the wake, suggesting that they were not propagating along a surface of wake boundary. The polarization was highly elliptic except for high frequency component. The magnetic field variation was predominantly perpendicular to the background magnetic field, suggesting that they were shear Alfven waves. The mechanism of unifying the polarization is not yet understood.