Summary: Imaging core flow from geomagnetic secular variation: Consequences
for core-mantle interactions and geomagnetic dipole moment changes
A dissertation submitted to The Johns Hopkins University in conformity with the
requirements for the degree of Doctor of Philosophy.
cHagay Amit 2005
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Flow in the fluid outer core just below the core-mantle boundary is inferred from ge-
omagnetic secular variation data, assuming frozen magnetic flux, tangential geostrophy,
and a new physical assumption termed helical flow. Helical flow, in which tangential di-
vergence correlates with radial vorticity, removes non-uniqueness in the inversion of the
magnetic induction equation. My flow solutions using geomagnetic field models from the
2000 Oersted and 1980 Magsat satellites resemble previous flow models, but contain more
flow along contours of radial magnetic field. I invert geomagnetic secular variation be-
tween 1895-1985 to isolate the time-average and time-dependent parts of the flow. The
most prominent flow structure is a large anti-cyclonic vortex in the southern hemisphere.