A Statistical Study of the Lunar Plasma Wake using ARTEMIS Measurements

The Moon does not have an intrinsic magnetic field and lacks the conductivity necessary to develop an induced magnetosphere. Therefore, the interaction of the Moon with the solar wind is dominated by impact absorption on the day side and the generation of a plasma wake on the night side. The ARTEMIS (Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon's Interaction with the Sun) spacecraft mission is a two-probe lunar mission derived from the THEMIS (Time History of Events and Macroscale Interactions During Substorms) mission, repurposed to study the lunar space and planetary environment. Over the course of the mission there have been numerous passes of the ARTEMIS spacecraft through the lunar wake, starting on February 13, 2010. The wake fly-bys have occurred in a variety of orbit geometries and distances from the planet, ranging up to many lunar radii downstream. They have also occurred for a variety of external conditions. In this presentation, we will share a statistical study of the numerous wake-crossing events of the ARTEMIS probes, using data primarily from the ARTEMIS fluxgate magnetometer (FGM) and electrostatic analyzers (ESAs) to identify when the spacecraft entered and exited the wake. Using the morphology of the wake boundary, we will determine the spatial extent of the lunar wake as a function of distance behind the Moon and its response to external conditions.