| |
|
|
| The World Digital
Magnetic Anomaly Map (WDMAM) shows the variation in strength of the
magnetic field after the Earth's dipole field has been removed. Earth's
dipole field is generated by circulating electric currents in the
planet's metal core. It varies from 35,000 nanoTesla (nT) at the Equator
to 70,000 nT at the poles.
Image: Korhonen, J.V.,
Fairhead, J.D., Hamoudi, M., Hemant, K., Lesur, V., Mandea, M., Maus,
S., Purucker, M., Ravat, D., Sazonova, T.,and Thebault, E., 2007,
Magnetic Anomaly Map of the World (and associated DVD), Scale:
1:50,000,000, 1st edition, Commission for the Geological Map of the
World, Paris, France.
 |
Most computers will open this document automatically, but
you may need Adobe Reader
|
After removal of the dipole field anomalies, the
variations in the field (few hundreds of nT) are due to changes in the
magnetic properties of the crustal rocks themselves.
Hot colours (reds) indicate high values; cold colours (blues)
indicate low or negative values of the magnetic field strength.
|
|
|
