Bar magnets have two poles. They make dipole magnetic fields. Magnetic fields can have more than two poles. Quadrupole fields have four poles.
Click on image for full size
Original artwork by Windows to the Universe staff (Randy Russell).
Dipole, Quadrupole, and Multipole Magnetic Fields
Have you ever seen a bar magnet? Bar magnets have two magnetic poles - north and south. The magnetic field around a bar magnet is called a dipole magnetic field. "Dipole" means "two poles".
Bar magnets are not the only things that make dipole fields. Electricity flowing through a coiled wire can cause a dipole magnetic field. The magnetic fields of some planets are pretty much dipole fields.
Dipoles are not the only shape magnetic fields come in. There are also quadrupole fields with four poles. Sometimes magnetic fields have six or even eight poles (an octupole!). Any field with more than two poles is called a multipole field.
Some planets, stars, and moons have magnetic fields. Some of those magnetic fields are pretty much dipoles. Others are more complex. They have a mix of dipole and multipole magnetic fields. The magnetic fields of Earth and Jupiter are mostly dipoles. They only have weak multipole parts. Uranus and Neptune have more complicated magnetic fields. The quadrupole parts of their fields are just as strong as the dipole parts!
Shop Windows to the Universe Science Store!
Our online store
on science education, ranging from evolution
, classroom research
, and the need for science and math literacy
You might also be interested in:
The force of magnetism causes material to point along the direction the magnetic force points. Here's another picture of how this works. This picture shows where the magnetic poles of the Earth are to...more
The Earth has a dipole magnetic field. This is when magnetic field lines point in a direction out of the South Pole and into the North Pole. Planets can also have quadrupoles (4 poles) and octupoles (8-poles)....more
Jupiter's magnetosphere is very special. It is the biggest thing in the entire solar system. Not only is it big enough to hold all of Jupiter's moons, but the sun itself could fit inside. It goes all...more
The magnetosphere of Uranus is medium sized, but still much bigger than the Earth's. It holds all of Uranus' moons. It is probably made in the middle of the planet, and with ice, rather than with iron...more
Uranus has a strange magnetic field. The magnetic poles of Uranus are not at all close to the geographic poles of Uranus. The main magnetic field of Uranus is tilted 59° away from the planet's spin axis....more
Mercury has a magnetic field. Its field is weak. Earth's magnetic field is tilted. So is Mercury's. That means Mercury's magnetic poles are not in the same place as its geographic poles. Mercury has a...more
A magnetometer is an instrument for measuring magnetic fields. Many spacecraft carry magnetometers to measure the magnetic fields around planets. When a spacecraft makes those measurements, what do the...more