Simulations

A snapshot of the simulated field of Glatzmaier and Roberts (1995) during normal polarity showing lines of magnetic flux with mainly dipolar character outside the core and tightly wound lines of magnetic flux inside the core. Blue (gold) color indicates field with inward (outward) component.

Gary Glatzmaier and Paul Roberts' simulation of the geodynamo is a physically self-consistent model in a 3-D spherical geometry appropriate for the core. It produces a dominantly dipolar field which is quite Earth-like in spatial spectral content, and it is the only one to date that undergoes spontaneous reversals of polarity. We are using paleomagnetic observations to evaluate the simulations and to better understand the behavior of the field and the conditions deep in the Earth that control how it is generated.

Geodynamo simulations for eight cases of different imposed patterns of heat flux through the core-mantle boundary. The total heat escaping the core is the same for each case. Solid red (dashed blue) contours denote greater (lesser) heat flux than the mean. Time is in terms of magnetic diffusion time for the core (20,000 yr). Zoom to enlarge.

Different field behavior is observed for the various heat flux cases. Some cases reversed frequently (A, C) and one didnÕt reverse at all (E). Case F almost died: the field intensity (dipole moment) dropped close to zero and stayed there. In the others the average intensity ranged from 10 to 75 percent of today's geomagnetic field strength. Case H has heat flux scaled to seismic velocity in the lower mantle revealed by deep-Earth tomography, more heat flowing into higher-velocity mantle where temperature is thought to be lower.

The relative spatial-spectral content of the simulations and Earth's geomagnetic field as observed by MAGSAT are similar, though the intensity is lower for all cases. Shown here are the homogeneous (G) and tomographic (H) heat flux cases.

 

Links: Case G Reversal | Case H Reversal | VGP Preference? | Case C Excursion | References

Home | Faculty | Graduate | Undergraduate | Contact | Computer Help | Seminars | Jobs | Alumni | Courses | UC Santa Cruz
Comments about this site should be directed to: webmaster@es.ucsc.edu