IAFE   05512
INSTITUTO DE ASTRONOMIA Y FISICA DEL ESPACIO
Unidad Ejecutora - UE
artículos
Título:
Structure of Titan s induced magnetosphere under varying background magnetic fi eld conditions: Survey of Cassini magnetometer data from fl ybys TA T85
Autor/es:
S. SIMON; S. VAN TREECK; A. WENNMACHER; J. SAUR; F. NEUBAUER; C. BERTUCCI; M. DOUGHERTY
Revista:
JOURNAL OF GEOPHYSICAL RESEARCH
Editorial:
AMER GEOPHYSICAL UNION
Referencias:
Año: 2013 p. 1 - 21
ISSN:
0148-0227
Resumen:
Cassini magnetic field observations between 2004 and 2012 suggest the ambient field conditions near Titans orbit to differ significantly from the frequently applied pre-Cassini picture (background magnetic field homogeneous and perpendicular to Titans orbital plane, stationary upstream conditions). In this study, we analyze the impact of these varying background field conditions on the structure of Titans induced magnetosphere by conducting a systematic survey of Cassini magnetic field observations in the interaction region during flybys TAT85 (July 2004July 2012). We introduce a set of criteria that allow to identify deviations in the structure of Titans induced magnetosphereas seen by the Cassini magnetometer (MAG)from the picture of steady-state field line draping. These disruptions are classified as weak, moderate, or strong. After applying this classification scheme to all available Titan encounters, we survey the data for a possible correlation between the disruptions of the draping pattern and the ambient magnetospheric field conditions, as characterized by Simon et al. [2010a]. Our major findings are: (1) When Cassini is embedded in the northern or southern lobe of Saturns magnetodisk within a ` 3 h interval around closest approach, Titans induced magnetosphere shows little or no deviations at all from the steady-state draping picture. (2) Even when Titan is embedded in perturbed current sheet fields during an encounter, the notion of draping the average background field around the moons ionosphere is still applicable to explain MAG observations from numerous Titan flybys. (3) Only when Titan is exposed to intense north- south oscillations of Saturns current sheet at the time of an encounter, the signatures of the moons induced magnetosphere may be completely obscured by the ambient field perturbations. (4) So far, T70 is the only flyby that fully meets the idealized pre-Cassini picture of the Titan interaction (steady background field perpendicular to Titans orbital plane, steady upstream flow, unperturbed induced magnetosphere).