Planetary Group Seminar: Energetic Neutral Atom imaging at Mars, Venus and Moon: Interactions between plasma, exosphere, and surface (Y. Futaana)
13:00 - 14:00
Swedish Institute of Space Physics
It is frequently said that 99% of all known matter in the universe is in the plasma state. To understand the universe, understanding of the behavior of the plasma is therefore essential. Traditionally, space plasma has been investigated using in-situ charged particle measurements, or electromagnetic emission (or absorption) lines. Recently, energetic neutral atom (ENA) imaging has opened a new channel for space plasma investigations. ENAs are produced mostly by the charge exchange mechanism in space; when an ion receives an electron from a neighboring neutral atom, the primary ion becomes an ENA. During the charge exchange process, the energy loss of the primary ion is negligible. Due to the neutrality, ENAs do not feel any electromagnetic force. Therefore, we can know the primary ion's velocity distribution function remotely using ENAs. In this presentation, we review recent achievement of ENA observations conducted at Mars, Venus, and Moon. We identified several populations of ENAs, and characterized them. As future missions, ENA sensors will be inserted to Mercury (with BepiColombo) and to Jupiter (with JUICE). We also predict the anticipated results from these future observations.