Abstract The study of lunar near-surface electron density provides crucial insights into the Moon’s space environment and its interaction with solar wind. The present work discusses the changes in the lunar near surface plasma environment when moon is in the geomagnetic tail, just prior to, during, immediately after and 24 hours after the hop (in terminator and outside the geotail) of Chandrayaan 3 Lander. The results obtained from the Langmuir probe measurements along with model simulations, highlight the variations in electron density (Ne) from ≈478/cc before hop, to ≈26/cc during and immediately after hop as well as ≈1100/cc at the terminator. Substantial reduction in ambient ionization during hop is modeled in terms of the lander firing induced hot exhaust and consequent movement of neutral species away from the lander vicinity and ensuing reduced refilling. In the terminator, the (Ne) increases to ≈1100/cc due to the combined effects of increased neutral densities and consequent increased production. The mean electron temperatures (Te) obtained during the sweep mode operation just prior to hop and in terminator are ≈2600 K and ≈3300 K respectively. The Lunar Ionospheric Model (LIM) is used to bring out the role of photo-ionization of molecular species along with solar wind proton /magnetospheric proton charge exchange processes and solar wind pick up/geomagnetic field related removal of ions in modulating the lunar ionosphere during the varying phases. Thus, the hop experiment enabled the study of the response of the lunar ionosphere to impulsive changes in the ambient atmosphere due to man-made (lander operation) and natural causes.
Manju et al. (Sat,) studied this question.