Science Opportunities - Basic Research Opportunities in Earth Science - page 67

Geomagnetic Studies
High-performance computing has allowed the first realistic simulations of
the convective dynamo that creates the geomagnetic field. These numerical
simulations have been used to explore the possible consequences of changing
thermal boundary conditions at the core-mantle boundary and have made
intriguing predictions about the possible connections between the geodynamo and
mantle dynamics. Analyses of the historical magnetic field show long-standing
features that persist for at least hundreds of years, and comparison with the time-
averaged field over 5 million years reveals intriguing similarities ( Figure 2.16 ).
The newest generation of paleomagnetic instrumentation provides measurements
of an unprecedented quality. Coupled with careful field work, these new
instruments permit reliable estimates of field paleointensity. Short-term variations
in both direction and intensity not only furnish a means for making high-
resolution stratigraphic correlations, but also place important constraints on the
processes that generate the geomagnetic field. In particular, the new data can be
used to develop a more detailed understanding of magnetic field reversals, and
the time-averaged field can be used to understand long-term deviations from an
axial dipole. Finally, extending the geographical coverage of high-resolution
paleomagnetic records obtained from sediments and igneous rocks is critical for
testing predictions made by core dynamo models. Drilling into high-
sedimentation-rate, anoxic basins provides the best data for attaining these goals,
although paleomagnetic studies of continental rocks will also yield valuable
measurements.