Empirical Photochemical Modeling of Saturn’s Ionization Balance Including Grain Charging

Abstract We present a semianalytical photochemical model of Saturn’s near-equatorial ionosphere and adapt it to two regions (∼2200 ∼1700 km above the 1 bar level) probed during inbound portion Cassini’s orbit 292 (2017 September 9). The uses as input measured concentrations molecular hydrogen, hydrogen ion species, free electrons, well electron temperature. output includes upper limits, or constraints, on mixing ratios families molecules, concentrations, attachment rates electrons ions onto dust grains. suggests that, particularly near km, differ notably from what independent measurements by Ion Neutral Mass Spectrometer suggest. Possibly connected this, an electron-depleted plasma with level depletion around 50%. This is in qualitative agreement interpretations Radio Plasma Wave Science/Langmuir Probe measurements, but additional conundrum arises fact that coherent equilibrium scenario then relies component typical grain radii smaller than 3 Å.