Dynamical and magnetic field time constants for Titan's ionosphere: Empirical estimates and comparisons with Venus

• Autores: Cravens, T. E.; Richard, M.; Ma, Y. J.; Bertucci, Cesar; Luhmann, J. G.; Ledvina, S.; Robertson, I. P.; Wahlund, J. E.; Ågren, K.; Cui, J.; Muller Wodarg, I.; Waite, J. H.; Dougherty, M.; Bell, J.; Ulusen, D.
• Año de publicación: 2010
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Ionosphere: Ionosphere/magnetosphere interactions; Ionosphere: Ionosphere/atmosphere interactions; Ionosphere: Ionospheric dynamics; Planetary Sciences: Comets and Small Bodies: Ionospheres (2459), Planetary Sciences: Solar System Objects: Titan
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

Plasma in Titan´s ionosphere flows in response to forcing from thermal pressure gradients, magnetic forces, gravity, and ion-neutral collisions. This paper takes an empirical approach to the ionospheric dynamics by using data from Cassini instruments to estimate pressures, flow speeds, and time constants on the dayside and nightside. The plasma flow speed relative to the neutral gas speed is approximately 1 m s^‑1 near an altitude of 1000 km and 200 m s^‑1 at 1500 km. For comparison, the thermospheric neutral wind speed is about 100 m s^‑1. The ionospheric plasma is strongly coupled to the neutrals below an altitude of about 1300 km. Transport, vertical or horizontal, becomes more important than chemistry in controlling ionospheric densities above about 1200-1500 km, depending on the ion species. Empirical estimates are used to demonstrate that the structure of the ionospheric magnetic field is determined by plasma transport (including neutral wind effects) for altitudes above about 1000 km and by magnetic diffusion at lower altitudes. The paper suggests that a velocity shear layer near 1300 km could exist at some locations and could affect the structure of the magnetic field. Both Hall and polarization electric field terms in the magnetic induction equation are shown to be locally important in controlling the structure of Titan´s ionospheric magnetic field. Comparisons are made between the ionospheric dynamics at Titan and at Venus.
Fil: Cravens, T. E.. University of Kansas; Estados Unidos
Fil: Richard, M.. University of Kansas; Estados Unidos
Fil: Ma, Y. J.. University of California; Estados Unidos
Fil: Bertucci, Cesar. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina
Fil: Luhmann, J. G.. University of California; Estados Unidos
Fil: Ledvina, S.. University of California; Estados Unidos
Fil: Robertson, I. P.. University of Kansas; Estados Unidos
Fil: Wahlund, J. E.. Swedish Institute of Space Physics; Suecia
Fil: Ågren, K.. Swedish Institute of Space Physics; Suecia
Fil: Cui, J.. Imperial College London; Reino Unido
Fil: Muller Wodarg, I.. Imperial College London; Reino Unido
Fil: Waite, J. H.. Southwest Research Institute; Estados Unidos
Fil: Dougherty, M.. Imperial College London; Reino Unido
Fil: Bell, J.. Southwest Research Institute; Estados Unidos
Fil: Ulusen, D.. University of California; Estados Unidos