Use this URL to cite or link to this record in EThOS:
Title: Studies of 10 hour periodicity in Saturn's magnetosphere
Author: Espinosa, Stephane Alexandre
ISNI:       0000 0004 2737 3624
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2001
Availability of Full Text:
Access from EThOS:
Access from Institution:
Studies of 10 hour periodicity are especially interesting in the context of Saturn's magnetosphere, because the current knowledge and understanding of the Saturn system do not provide a satisfactory explanation for modulations with this type of periodicity. The planetary internal magnetic field has been modelled as exactly axisymmetric, and therefore cannot account for periodic observations with a period close to that of planetary rotation (10 hours 39.4 minutes). Nevertheless, such 'spin-periodic' modulations are present in a few data sets, including the kilometric radio emissions and the aurora observations. These elements suggest an as yet undetected longitudinal asymmetry in the planetary magnetic field, hence the interest in carrying out a detailed analysis of the magnetic field data to ensure that all the valuable information is obtained. Only three spacecraft have encountered Saturn so far (Pioneer 11, Voyager 1 and 2), each time as a single fiy-by, hence the scarcity of the in-situ observations and the importance of expressing all the available magnetic field data in a standard coordinate system, chosen as planetocentric spherical polar. As a result of a thorough data analysis, the magnetic field in fact presents a spin-periodic perturbation almost throughout the observations. A list of unlikely causes, including a tilt of the magnetic dipole axis, is provided, in order to understand well the difiiculties raised by these new results. Finally, the 'Camshaft model' is proposed, based on a hypothetical anomaly (possibly magnetic) at Saturn and the generation of magnetohydrodynamic waves in the fast mode. These waves produce a local spin-periodic perturbation of the magnetic field, independently of the level of plasma sub-corotation. This conceptual model is very successful in explaining qualitatively the magnetic field observations, and the initial hypothesis should be verified by the Cassini spacecraft that will accurately determine the planetary internal magnetic field.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available