Journal of Geophysical Research: Space Physics Statistical characterization of the foremoon particle and wave

Abstract Although the zeroth-order picture of the Moon-solar wind interaction involves no upstream perturbation, the presence of the Moon does affect the upstream plasma in a variety of ways. In this paper, a large volume of data obtained by the dual-probe Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon’s Interaction with the Sun (ARTEMIS) mission are used to characterize the large-scale morphology of the “foremoon, ” which is defined as the region upstream of the Moon and its wake that contains Moon-related particles and waves. Solar wind ions reflected from the unshielded surface and by crustal magnetic fields, together with heavy ions of lunar surface/exospheric origin, are picked up by the solar wind magnetic and electric fields. Partially coinciding with populations of these Moon-related ions, ∼0.01 Hz and ∼1 Hz magnetic field fluctuations are observed. The morphology of the Moon-related ion and wave distributions is well organized by the upstream magnetic field direction. In addition, the low-frequency wave distributions depend on the upstream Alfvén Mach numbers, suggesting that propagation effects also play a role in determining the wave foremoonmorphology. Occurrence of modified electron velocity distributions and higher-frequency, electromagnetic, and electrostatic waves is primarily controlled by magnetic connection to the Moon and its wake. These statistical results observationally demonstrate the large-scale properties of the foremoon and upstream-parameter control thereof. 1