We present statistical analyses of whistler-mode waves observed by Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon’s Interaction with the Sun (ARTEMIS). Although some observations showed rising tone elements of the lunar whistler-mode waves similar to the terrestrial chorus emissions, it remains unknown whether a banded structure typically seen in chorus is common to the lunar waves. In this study, we automatically detected whistler-mode waves from 9 years of ARTEMIS data and classified them into four types of spectral shapes: lower band only, upper band only, banded, and no-gap. We first show that magnetic connection to the lunar surface is a dominant factor in the wave generation; the occurrence rate of whistler mode waves is more than 10 times larger on magnetic field lines connected to the Moon than on unconnected field lines. Then we compared the field line connected events according to the position of the Moon and the condition of the field-line foot point (day/night and existence of lunar magnetic anomalies). The results show that (i) almost no banded event is observed in any circumstances, suggesting that generation mechanisms for the two band structure on the terrestrial chorus are largely ineffective around the Moon, and (ii) the wave occurrence rate depends on the foot point conditions, presumably affected by electrostatic/magnetic reflections deforming the velocity distribution of the resonant electrons. Thus, our results provide implications for the two band structure formation and new insights to fundamental processes of the Moon-plasma interaction.
