Premium
Fluid flow near the surface of Earth's outer core
Author(s) -
Bloxham Jeremy,
Jackson Andrew
Publication year - 1991
Publication title -
reviews of geophysics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 8.087
H-Index - 156
eISSN - 1944-9208
pISSN - 8755-1209
DOI - 10.1029/90rg02470
Subject(s) - dynamo theory , geology , geophysics , secular variation , mantle (geology) , outer core , flow (mathematics) , inner core , earth's magnetic field , core–mantle boundary , geomagnetic secular variation , core (optical fiber) , mechanics , physics , dynamo , magnetic field , quantum mechanics , geomagnetic storm , optics
Maps of the fluid flow at the core surface are important for a number of reasons: foremost they may provide some insight into the workings of the geodynamo and may place useful constraints on geodynamo models; from the flow, the force balance at the top of the core can, at least in part, be deduced; the flow can provide short‐term predictions of the secular variation; the flow is important in understanding changes in the length of day; and constraints on lateral temperature variations and topography at the core‐mantle boundary may be derived. Unlike the case of mantle convection, only very small lateral variations in core density are required to drive the flow; these density variations are too small (by several orders of magnitude) to be imaged seismically, so instead we use the geomagnetic secular variation to infer the flow. Despite considerable recent progress in mapping the core flow, substantial differences exist between maps produced by different researchers. Here we examine the possible underlying reasons for these differences, paying particular attention to the inherent problems of nonuniqueness. We focus on the aspects of the flow which do seem to be well determined and discuss their geophysical implications.