Gravity + Magnetics

Where does gravity act towards?

The centre of mass.

Field lines enter Earth at 90 and leave at magnetic south pole.

What are dipoles?

Like Bar magnets.

What is the formula for inclination?

What formula do you use for induced magnetism?

How does the Earth’s body induce magnetisation?

A magnetic dipole parallel to the direction of the inducing field.

When do you get a positive anomaly?

Observed field = Earth’s field + Induced field

Large observed field: positive anomaly - reinforce each other

When do you get a negative anomaly?

Small observed field: negative anomaly - oppose each other

Can you use rock type to determine susceptibility?

No.

What is the formula for gravitational force?

What is the formula for the magnetic field strength of a dipole?

H = 1/r³

What is similar about magnetics and gravity?

Both induced fields decay rapidly with distance.

Magnetics is more rapidly.

What is the anomaly strength controlled by?

• Distance from magnetic body

• Spacing of induced field lines

• Relative direction of induced and inducing field.

What is remanent magnetisation?

What’s the difference between inclination and declination?

Why do we assume there is no remanent magnetism in the observed magnetic field?

It is time consuming and expensive.

What is a proton precession magnetometer?

Measures the total amplitude of the Earth’s magnetic field.

What are the three main methods to acquire magnetic data?

What two parameters do magnetic anomalies depend on?