Using Lunar Prospector magnetic field data, we identify four isolated anomalies (C_NA, C_SA1, C_SA1, and C_WA) within the Crisium basin. We assume the sources of the anomalies to be buried point dipoles and find that the estimated depths and radial positions are well contained within Crisium's melt pool (∼250‐km radii and ∼100‐km depth). This implies that the anomalies recorded a thermoremanent magnetization in a dynamo field at ∼3.9 Ga. We also find that the anomalies can be classified into two groups (Groups 1 and 2) according to source depths and paleopoles. The sources of Group 1 (C_NA and C_SA1) are buried at ∼30 km. Estimated paleopoles are located at ∼45°N for C_NA and near the equator (∼12°N) C_SA1, with remanence acquisition timescale of ∼5 Myr. The sources of Group 2 (C_SA2 and C_WA) are more deeply buried at ∼55–70 km. Their paleopole positions are close to the present south pole, with a remanence acquisition timescale of ∼15–23 Myr. These variable paleopoles imply that the local field orientation shifted during formation of the anomalies. That is, the Moon may have experienced a ∼14‐Myr‐epoch of complex field geometries. These changes may have arisen from true polar wander driven by impact or internal density changes, or from equatorial dynamo orientations produced by anomalous core heat flux conditions. The long cooling timescales of the anomalies also suggest that they were not magnetized by transient fields produced by impact‐induced stirring of the core.

We report an example of large electric field with a peak amplitude of ∼60 mV/m observed at the plasmapause by the Polar spacecraft on April 25, 1998. This electric field pointed radially outward and predominantly perpendicular to the ambient magnetic field. As comparing the plasmapause crossings in the previous and following Polar passes, we found that the large electric field is associated with forming a sharp plasmapause structure. Comparing with previous observations of subauroral electric fields in the ionosphere and magnetosphere, we suggest that the large electric field observed at Polar is associated with the subauroral ion drift phenomenon. In addition, we observed a negative‐then‐positive magnetic field perturbation at the plasmapause. That is, the magnetic field is reduced outside the plasmapause and enhanced inside the plasmapause. The field perturbation is dominant in the meridional plane. We suggest that the magnetic field perturbation is due to the dawnward plasmapause current (J_pp), which is associated with the balance of forces (∇P ∼ J_pp × B) at the plasmapause, perpendicular to the background magnetic field.

Kplo-MAGnetometer (KMAG) is one of the scientific instruments of Korea Pathfinder Lunar Orbiter (KPLO) set to be launched in 2022. Its objectives are magnetic field investigation and technical demonstration near the surface of the Moon. Specifically, it will investigate the lithospheric magnetism of the Moon and measure the electromagnetic wave properties near the lunar surface. It consists of three fluxgate magnetometers on a 1.2 m long boom, which is relatively shorter than the boom used in other missions. The three magnetometers are included for scientific measurements, redundancy checks, and multi-sensor technical investigation. The magnetometers and an inner Anisotropic Magneto-Resistive sensor perform simultaneous sampling to correct for the magnetic field interference caused by the spacecraft. The fully integrated flight model assembly showed that the magnetometer noise level was less than 30 pT Hz^−1/2 at 1 Hz and stability was within ±0.2 nT at the 10 Hz sampling rate. This paper describes the configuration and performance of the KMAG using the multi-sensing method. KPLO, THEMIS-ARTEMIS spacecraft, and Commercial Lunar Payload Service modules will be in their operational phase simultaneously. Therefore, the KMAG will be able to contribute to multi-site in-situ measurements of the lunar magnetic field. We expect that the KMAG will provide an up-to-date lunar observation data set and an opportunity to perform the multi-sensor observation.

The Korean Pathfinder Lunar Orbiter (KPLO)-MAGnetometer (KMAG) consists of three triaxial fluxgate sensors (MAG1, MAG2, and MAG3) that measure the magnetic field around the Moon. The three sensors are mounted in the order MAG3, MAG2, and MAG1 inside a 1.2 m long boom, away from the satellite body. Before it arrived on the Moon, we compared the magnetic field measurements taken by DSCOVR and KPLO in solar wind to verify the measurement performance of the KMAG instrument. We found that there were artificial disturbances in the KMAG measurement data, such as step-like and spike-like disturbances, which were produced by the spacecraft body. To remove spacecraft-generated disturbances, we applied a multi-sensor method, employing the gradiometer technique and principal component analysis, using KMAG magnetic field data, and confirmed the successful elimination of spacecraft-generated disturbances. In the future, the proposed multi-sensor method is expected to clean the magnetic field data measured onboard the KPLO from the lunar orbit.

3-D simulations for lunar sodium exosphereReproduction of lunar sodium brightness near the MoonReproduction of sodium brightness and velocity distribution at tail