2:00 PM - 2:15 PM
[PPS08-14] Macroscale Properties of Lunar Surface Magnetic Fields in the Solar Wind: Insights from Apollo-Era Data
Keywords:Lunar surface magnetic field, Crustal magnetism, Solar wind interaction, Apollo Lunar Surface Experiments Package
The magnetic field of the Moon provides valuable insights into various aspects of lunar science. The primary source of the lunar magnetic field is crustal magnetization, and its distribution offers clues about the evolution of the lunar dynamo. Unlike Earth or Mars, which have dense atmospheres, the Moon is directly exposed to the solar wind, a space weathering process that can alter the properties of the lunar surface. One of the most pressing unanswered questions in lunar science today is whether lunar swirls form due to localized magnetic fields influencing space weathering. Additionally, the lunar magnetic field plays a crucial role in surface charging, as it reflects electrons more effectively and can contribute to a positive surface potential. Despite their significance, data collected during the Apollo era remain underexamined in the context of understanding the interaction between the lunar surface magnetic field and the solar wind.
This study utilizes data from three sources: Lunar Surface Magnetometer (LSM) data from Apollo 12, 15, and 16; Solar Wind Spectrometer (SWS) data from Apollo 12 and 15; and the OMNI solar wind dataset. Cross-comparison of these datasets reveals large-scale properties of solar wind interactions with the lunar surface. The Apollo 12, 15, and 16 landing sites exhibit distinct levels of crustal magnetization. By comparing LSM data with solar wind measurements, I have derived the best estimates of the local magnetic field at these three Apollo sites by removing the effects of the interplanetary magnetic field and solar wind dynamic pressure. My results indicate that the stronger the local crustal field, the less the surface magnetic field correlates with the IMF, suggesting additional effects arising from interactions between the solar wind and the crustal magnetic field. Furthermore, the solar wind dynamic pressure and zenith angle emerge as two major factors influencing the strength and orientation of surface magnetic field variations.
Simultaneous measurements from the Apollo 12 and 15 SWS instruments provide further insights into the interaction between the solar wind and the crustal magnetic field. Cross-comparisons between datasets reveal that at the Apollo 15 site, where crustal magnetization is minimal, solar wind particles are nearly identical to those in the external environment. The results indicate that the local magnetic field at the Apollo 12 site can either increase or decrease plasma density and velocity, depending on the local time at the station and the corresponding solar wind zenith angle.
This study utilizes data from three sources: Lunar Surface Magnetometer (LSM) data from Apollo 12, 15, and 16; Solar Wind Spectrometer (SWS) data from Apollo 12 and 15; and the OMNI solar wind dataset. Cross-comparison of these datasets reveals large-scale properties of solar wind interactions with the lunar surface. The Apollo 12, 15, and 16 landing sites exhibit distinct levels of crustal magnetization. By comparing LSM data with solar wind measurements, I have derived the best estimates of the local magnetic field at these three Apollo sites by removing the effects of the interplanetary magnetic field and solar wind dynamic pressure. My results indicate that the stronger the local crustal field, the less the surface magnetic field correlates with the IMF, suggesting additional effects arising from interactions between the solar wind and the crustal magnetic field. Furthermore, the solar wind dynamic pressure and zenith angle emerge as two major factors influencing the strength and orientation of surface magnetic field variations.
Simultaneous measurements from the Apollo 12 and 15 SWS instruments provide further insights into the interaction between the solar wind and the crustal magnetic field. Cross-comparisons between datasets reveal that at the Apollo 15 site, where crustal magnetization is minimal, solar wind particles are nearly identical to those in the external environment. The results indicate that the local magnetic field at the Apollo 12 site can either increase or decrease plasma density and velocity, depending on the local time at the station and the corresponding solar wind zenith angle.