HR: 08:30h
AN: P31A-03    [PDF]
TI: Models for Mars' Magnetic Scalar Potential
AU: * Jurdy, D M
EM: donna@earth.northwestern.edu
AF: Northwestern University, Department of Geological Sciences; 1850 Campus Drive, Evanston, IL 60208-2150 United States
AU: Stefanick, M
EM: mike@earth.northwestern.edu
AF: Northwestern University, Department of Geological Sciences; 1850 Campus Drive, Evanston, IL 60208-2150 United States
AB: Mars Global Surveyor MAG/ER measured strongly magnetized crust, despite Mars' weak field at present, the intensity reaches about 10 times that of Earth's magnetic lineations. We analyze the magnetic lineations in an octant centered at $40\deg$S, $180\deg$W $\pm40\deg$, concentrated in the more heavily cratered Southern hemisphere. Data from the mapping phase of Mars Global Surveyor, MAG/ER magnetic measurements at an altitude of 404 $\pm34$ km, were made available by Connerney conveniently binned into degree boxes. Using a rotated spherical co-ordinate system centered at $40\deg$S, $180\deg$W, we perform a two-dimensional Fourier analysis over this region. This can be shown to be a good approximation: results can be used to reconstruct the original components as a check. The magnetic field components can be described by the curl of a vector potential or the gradient of a scalar potential. The scalar potential is especially attractive as it can be obtained from the Fourier transform of the vertical magnetic component, H$_{z}$. The gradient of this field generates the horizontal magnetic components which can be compared with the rotated horizontal components. The corresponding fields are nearly identical, thus an independent check as the horizontal components were not used to construct the scalar potential. We model the magnetic field using the observed scalar potential. With vertical dipoles we determine depths and magnitudes for selected centers and average surroundings, and find that 8 sources account for 80% of the variance. (Only 4 sources already account for 60% of the variance.) These sources range in depth 260$\pm130$ km, and the source magnitudes range over a factor of 4. Using the autocorrelation of the scalar potential, we estimate that there are only 20-30 independent components of the field (which corresponds to a resolution of 4x5 or 5x6).
DE: 5440 Magnetic fields and magnetism
DE: 6055 Surfaces and interiors
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2003 Fall Meeting