One Dimensional Multispecies Magnetohydrodynamic Models of the Ionosphere of Titan and the Inner Coma of Comet P/halley
Abstract
The interaction of the Saturnian magnetosphere with the ionosphere of Titan exhibits many parallels to the solar wind interaction with non-magnetic bodies in the solar system. A one-dimensional magnetohydrodynamic model was developed, for radial distances from 1.3-2 R _{rm T}, to study the dynamics of H_2CN^+ , C_{rm n}H _{rm m}^+(rm n,m>2), C_2H_5 ^+, and CH_5^+, in the ramside ionosphere of Titan. A hydrodynamic model was employed to study the wakeside ionosphere and included the additional ions H^+, H _2^+, and H_3^+, as well as plasma transport along magnetic field lines. The sources of ionization and the electron temperatures included in the model are affected by the relative locations of Titan, Saturn, and the sun. For the case of a dayside -ramside ionosphere (solar zenith angle of 60^ circ) we found that the external magnetospheric plasma interacting with Titan's ionosphere produced a very broad region of ionospheric magnetic field with a peak magnetic field strength of ~26 nT. The ionosphere was magnetized well below the ionospheric peak, allowing ionizing Saturnian magnetospheric electrons access to this region. On the wakeside, we found outward ion flows of about 2times10^6 cm ^{-2} s^ {-1}, resulting in a total ion loss from Titan into Saturn's magnetosphere of about 6times10 24 s^{-1 }. We also developed a multispecies model to extend the work which Cravens (1987,1989) used to predict the existence of a narrow (50 km) layer of enhanced plasma density (factor of 3 over background) at the boundary of the Comet Halley diamagnetic cavity. For eighteen ion species we investigated factors affecting the magnitude of the density enhancement and its relationship to the thickness of the transition layer. Ion species with short chemical lifetimes are shown to have smaller density enhancements than species with longer lifetimes. The cometocentric distance of the cavity boundary also strongly affects the magnitude of the density enhancement; the enhancement increases with increasing distance.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- January 1992
- Bibcode:
- 1992PhDT........66K
- Keywords:
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- COMET HALLEY;
- MAGNETOSPHERE;
- Physics: Fluid and Plasma, Physics: Astronomy and Astrophysics