3.0 Overview

3.1 Magnetic Fields

• Oersted and Ampere
• The definition of magnetic induction, B
• Fields of a small loop (dipole)
• Magnetic fields in matter
• ferromagnetism
• magnetization, M
• magnetic susceptibility, c _m
• magnetic field, H
• remanent and induced M (hysteresis)

• The main dipole field
• Components of the vector field
• Secular variation in the main field
• External sources and the geomagnetic frequency spectrum

• The characteristics of magnetic anomalies
• Anomalies of simple shapes
• The sphere
• Demagnetization
• The half space
• The thin layer
• The quarter space
• The magnetic pole
• A line of poles
• Horizontal cylinders of polygonal section
• Poisson's relationship between g and H
• The magnetic field of an arbitrary 3D body

• Magnetic minerals
• Magnetite
• The effect of grain size
• c_m vs. the volume fraction of magnetite
• Remanent vs. Induced in rocks

• The dip needle
• The fluxgate magnetometer
• The proton precession magnetometer

• Sampling
• Time variations
• Gradiometers
• Processing

• Magnetic Anomalies due to a polygon