Geomagnetism: Earth’s magnetic field Dipole Field

Geomagnetism: Earth’s magnetic field

Dipole Field

Strength of Earth’s magnetic field (nT)

Higher order poles

Power spectrum of Earth’s magnetic field

Inclination of Earth’s magnetic field

Inclination of Earth’s magnetic field

Inclination and Declination

Inclination is relatedto latitude

Declination dependson horizontal components

Declination of Earth’s magnetic field

Magnetic North Pole vs. time

Magnetic vs. Geographic coordinates

Dipole driftswestward at:0.044 - 0.14°/century(2500-8000 yr period)

Non-dipole featuresdrift westward at:0.2 – 0.7°/century(550-1650 yr period)

Geomagnetic field strength is decreasing:Will fall to zero in the year 4000:The beginning of a reversal?

Paleomagnetism:Study of geomagnetic field vs. time

Spinner magnetometer

Astatic magnetometer

Cryogenicmagnetometer

Axial Geocentric Dipole Hypothesis: average over 104 yearsis geographic pole

tan I = 2 tan λ Plio-Pleistocene paleomag poles

Calculating a paleomagnetic pole

Baked contact test

Reversals Test

Apparent Polar Wander paths

Paleo Reconstructions

Magnetic Reversals

Magnetic Reversals vs. Time