A Topical Study of Planetary Magnetic Fields

We investigate multiple aspects of planetary magnetic fields and develop insights into several problems. We present new models of the magnetic field of Saturn using data from the Cassini-Huygens mission. We simultaneously find the simplest models that satisfy the data and solve for Saturn's rotation period. We systematically search for the rotation period that minimizes the misfit of its associated magnetic field model to the data. We do not unambiguously resolve the rotation period, implying a very axisymmetric field morphology. We place a bound on the amount of non-axisymmetry. We thus necessarily find a zonal model for Saturn's magnetic field, which is similar to models previously described, but better constrained.;To account for limited geographical data coverage of a planet by a satellite we develop and investigate spherical Slepian basis functions as an alternative to spherical harmonics in the analysis of planetary magnetic fields. We successfully adapt the functions to magnetic field analysis but find they generally underperform with respect to traditional spherical harmonics, with the exception of very specific geometries for which they are clearly better suited.;For Earth we examine the interaction between its paleomagnetosphere and the solar wind for a Young Sun. Using magnetohydrodynamic simulations we find plausible young solar wind conditions with which we force the paleomagnetosphere and determine its response to different conditions. We constrain solar mass flux and magnetosphere shape and size as a result.;We assess the thermal evolution of early solar system planetesimals and determine which parameters are relevant for the occurrence and longevity of a thermal convection dynamo. Planetesimals almost always meet conditions for a dynamo as they cool down from an initially hot and vigorously convecting state. However, these dynamos are very short-lived. We find minimum radii for planetesimals with long-lived dynamos which has implications for the prevalence of such bodies. Consideration of the evolution of planetesimals' lid thickness is critical to this problem. We can neglect the possibility of surface recycling based on basal stress calculations. We find an approximate analytical solution for the longevity of a dynamo as a function of radius and mantle viscosity.