Takaaki Tanaka

In contrast to many ground‐based optical observations of the thin lunar alkali exosphere, in situ observations of the exospheric ions by satellite‐borne plasma instruments have been quite rare. MAP‐PACE‐IMA onboard Japanese lunar orbiter SELENE (KAGUYA) succeeded in detecting Moon originating ions at 100 km altitude. Here we make the first report of the ion detection during intervals when the Moon was embedded in the Earth's magnetotail lobe. In the absence of plasma effects on the source process, ion species of H⁺, He⁺⁺, He⁺, C⁺, O⁺, Na⁺, K⁺ and Ar⁺ are definitively identified. The ion fluxes were higher when the solar zenith angle was smaller, which is consistent with the idea that the solar photon driven processes dominates in supplying exospheric components.