Plasma-neutral gas interactions in various space environments beyond simplified approximations

<p>The majority of the atmospheres of solar system bodies are composed of neutral gas, and hence their upper atmosphere are always partially ionized by the solar UV and collisions, allowing a complex nonlinear interaction with interplanetary plasma. &#160;Thus, ion-neutral and electron-neutral interaction plays a key role in this transition regions (ionosphere for planets and moons). However, our current understanding of plasma-neutral gas interactions is very limited due to lack of observations with proper instrumentation and to the difficulty in making laboratory experiments (almost impossible to reproduce the ionosphere with low energy plasma). &#160;Particularly the effect of small amount of neutral species in space above the exobase and the effects of electric charges on neutrals have been underestimated. &#160;</p> <p>To advance our knowledge of these basic but still poorly understood interactions between plasma and neutral gas at key regions of energy, momentum, and mass exchange between the space and the atmosphere, we evaluate what kind of measurement package is needed for different solar system objects in a cost-effective manner. &#160;We particularly focus on understanding the re-distribution of externally provided energy to the composing species through this interaction. &#160;</p> <p>The presentation is based on a white paper submitted to ESA's Voyage 2050 (Experimental Astronomy, 2022), and related mission proposals to space agencies. &#160;Here we skip the chemical aspect that is also mentioned in the white paper.</p> <p>Reference: https://doi.org/10.1007/s10686-022-09846-9</p>