One‐dimensional multispecies hydrodynamic models of the wakeside ionosphere of Titan

Abstract

The passage of Voyager 1 through the wakeside region of Titan's ionosphere provided an interesting probe of this plasma environment. A one‐dimensional multispecies hydrodynamic model was developed to study the wakeside ionosphere for radial distances ranging from 1.3 to 4.5 R T and included the ion species H 2 CN + , C n H m , C 2 H 5 + , CH 5 + , H + , H 2 + , and H 3 + . Plasma transport only along magnetic field lines was included. The only source of ion production was from electron impact ionization of Titan's atmosphere by radially streaming Satumian magnetospheric electrons (i.e., the nightside wakeside ionosphere). We found that ion production rates due to hot (200 eV) magnetospheric electrons impacting Titan's neutral atmosphere along radial field lines were comparable to the dayside ion production rates due to solar EUV flux. The magnetic flux tube area was varied along with electron temperature, and the results were compared to the ion densities and velocities measured during the Voyager 1 encounter. We found outward ion flows of about (2‐7) × 10 6 cm −2 s −1 , resulting in a total ion loss from Titan into Saturn's magnetosphere of about (6 ‐ 20) × 10 24 s −1 .