Electrostatic Waves and Electron Heating Observed over Lunar Crustal
Magnetic Anomalies
Abstract
Above lunar crustal magnetic anomalies, large fractions of solar wind
electrons and ions can be reflected and stream back towards the solar
wind flow, leading to a number of interesting effects such as
electrostatic instabilities and waves. These electrostatic structures
can also interact with the background plasma, resulting in electron
heating and scattering. We study the electrostatic waves and electron
heating observed over the lunar magnetic anomalies by analyzing data
from the Acceleration, Reconnection, Turbulence, and Electrodynamics of
Moon’s Interaction with the Sun (ARTEMIS) spacecraft. Based on the
analysis of two lunar flyby events in 2011 and 2013, we find that the
electron two-stream instability (ETSI) and electron cyclotron drift
instability (ECDI) may play an important role in driving the
electrostatic waves. We also find that ECDI, along with the modified
two-stream instability (MTSI), may provide the mechanisms responsible
for substantial isotropic electron heating over the lunar magnetic
anomalies.