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Simulating Imaging of Large Scale Radio Arrays on the Lunar Surface
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Identifying Ultra Low Frequency Waves in the Lunar Plasma Environment Using Trajectory Analysisand Resonance
S K Howard1, J S Halekas1, W M Farrell2
1Department of Physics and Astronomy, University of Iowa, Iowa City, IA, USA.
Journal of Geophysical Research. Space Physics
|January 28, 2021
Summary
Localized lunar magnetic fields reflect solar wind protons, driving plasma waves. A new method using reflected ion trajectories and Doppler shifts identifies these ultralow-frequency waves, crucial for understanding lunar space weather.
Area of Science:
- Space Physics
- Plasma Physics
- Lunar Science
Background:
- Lunar crustal magnetic fields reflect solar wind protons.
- Reflected ions can generate plasma waves.
- Single-spacecraft observations complicate wave property determination due to Doppler shifts.
Purpose of the Study:
- Develop a technique to identify ultralow-frequency (ULF) waves at the Moon.
- Determine the intrinsic properties of ULF waves.
- Investigate the role of reflected ions in wave generation.
Main Methods:
- Combine reflected proton trajectory analysis with Doppler shift and resonance conditions.
- Analyze plasma wave data from the Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS) probes.
- Solve Doppler shift and cyclotron resonance equations.
Main Results:
- Identified ULF waves with right-hand circular polarization in the lunar reference frame.
- Determined conditions for reflected ions to excite observed waves.
- Simulated reflected ion trajectories matched ARTEMIS observations, supporting their role in wave generation.
Conclusions:
- Reflected ions are the primary driver of observed ULF waves.
- The developed method uniquely identifies upstream propagating, right-hand polarized waves.
- Wave generation is attributed to cyclotron resonance with reflected ions.
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