# Geomagnetism Flashcards

What is the equation for the magnetic potential?

V(r) = m*r/4πr^3, where m is the magnetic dipole moment from S->N

What is the equation for the magnetic field?

-μ0*∇V(r), where ∇ is in spherical polar coordinates

What are the equations for the 3 components of spherical polar coordinates for the magnetic field?

B(r) = 2*μ0*m*cosθ/4πr^3 B(θ) = μ0*m*sinθ/4πr^3 B(Ф) = 0

What are meridians?

Arcs of constant Ф in spherical polar coordinates

What is geomagnetic field strength measured with?

A magnetometer.

What does the magnetic field strength vary between at earths surface?

25 μT to 65 μT

What is the geomagnetic latitude?

Latitude analogues to geographical latitude, but defined relative to the magnetic poles.

What is the declination angle for geomagnetism?

Angle between the magnetic and geographical meridians.

What is the inclination angle for geomagnetism?

Angle between magnetic field and a horizontal on the surface.

What are 2 equations for the inclination angle?

tan(I) = B(r)/B(θ) = 2*cos(θ)/sin(θ)

tan(I) = 2*sin(λ)/cos(λ) = 2*tan(λ), where λ = 90 - θ

What are 3 important types of magnetism? How do they differ?

- Ferromagnetism (All spins aligned, generating strong B-field up to curie temp)
- Ferrimagnetism (spins on multiple sublattices of a crysta, some spins antialigned)
- Antiferromagnet (spins are all antialigned, so no net B-field)

What are the locations of the magnetic poles right now?

North: 193.710 degrees W, 86.395 degrees N

South: 136.419 degrees E, 64.245 degrees S

What type of magnet is the solid iron core of the Earth?

A giant ferromagnet, or geodynamo.

What is the curie temperature of iron, and what is the temperature of Earths core?

T(c) of iron = 1043 K

T(core) = 6000 K +/- 500 K

What does the temperature of Earths core mean for its magnetism?

- Far above curie temp
- Is not a permanent magnet
- Field strengths are very low