Sub-ion-gyro scale magnetic field compressions generated by the solar wind interaction with the moon

Abstract Short-period magnetic enhancements were detected by the MAP-LMAG magnetometer onboard Kaguya orbiting moon in solar wind at an altitude of 100 km. The duration was typically 10 s, which corresponds to 0.5 degrees latitude along orbit and a scale size 15 magnitude field enhanced up 1.5–3.6 times as large that preceding quiet periods. No such found upstream field. short-period categorized into 2 groups. One is sub-ion-gyro-scale limb compression terminator region nearly constant flared away from consistently with previously known compressions. deduced 11 km, 85 small reported It significantly smaller than typical proton gyroradius 50–100 km 1AU. other types appeared crossings discontinuities wind. Some them on nightside moon. A possible explanation they fields compressed ions reflected channeled back current sheet interplanetary tangential discontinuity, similar hot flow anomalies observed Earth’s bow shock. themselves not moon, while expanding can penetrate through be Graphical