This site may earn affiliate commissions from the links on this page. Terms of use.

magnetic field head

The world "pole" tends to hateful the "terminate" of something. If you and I are polar opposites, we're as far from one another as the space we're in will allow us to be — and that'south a common sense definition. Later all, the most famous poles by far are the Northward and the South poles of the World, which are oriented at opposite ends of a slightly elongated sphere. These locations are by far the virtually noticeable things about the planetary poles — but information technology's non what defines them. A new paper published this week in Geophysical Research Messages gets at this uncertainty with a startling new idea: non only accept the Earth'due south magnetic poles not always been at the ends of the planet, but there hasn't even always been two of them!

What a planetary magnetic pole is is an area of a planet's surface where the "lines" of that planet'southward intrinsic magnetic field are perpendicular to its surface. In other words, it's whatever place where the field lines that we draw to represent the force of a magnetic field are straight upwards and down, relative to the portion of the surface they're crossing. In a two-lobed magnetic field similar the Earth's, called a "di-polar" system, the poles will naturally fall at the end — but a di-polar organization is not the merely arrangement that can come most.

Earth's magnetic north pole, vs. true/geographic north pole

Earth'due south magnetic north pole, vs. truthful/geographic north pole

The Globe's magnetic field, and all other planetary magnetic fields, come about as the result of something called the planetary dynamo. All this is is the layers of the Globe rotating a very slightly different speeds than i another — in particular, the relative motion between layers of the planet's inner chaff, then-called "convection" of molten atomic number 26. As the fe circulates through the molten portions of the planet, it moves effectually the planet's solid cadre.

In an electrical generator, we have a magnetized system that we cause to motility — by introducing motion into a electrically conductive system with a stable magnetic field, we get a constant menstruum of electrons. Ability! In the Earth'southward magnetic dynamo, information technology works the other fashion around — we accept the movement of electrons in the electrically conductive iron, and we have the physical motion caused past convection of that iron within the Earth'southward crust. The consequence is a stable magnetic field.

magnetic field 2

Now, notice that the Earth's dipole is not perfectly aligned with the axis of rotation — it's really off by about 11 degrees. The reason for this is that the rotation and convection that cause this magnetic field are very complex, involving the interplay of heat, friction, and the Coriolis effect on rotating bodies. Today, with a fairly elementary molten layer over a solid core, this results in nothing more than a slight misalignment with the planet'southward rotational axis. Just the Globe wasn't always like this.

Cosmic Rays (Wikipedia)Back in the planet's early history, its cadre wasn't and so unproblematic, or stable. At a certain point, there had not been enough time elapsed to allow significant solidification of the core, meaning that the dynamo was entirely the result of a swirling storm of molten planet — much harder to model than the interior of the World today! Carnegie scientist Peter Driscoll tried, all the same, and by modeling the thermal lifetime of the Earth going all the way back to its inception, he was able to make predictions most what sort of magnetic field should have existed at each fourth dimension menses.

The geological record already showed that the planet'south magnetic field could possibly have gone haywire effectually a thousand years ago — and Driscoll's model predicts that effectually this fourth dimension, the dull solidification of the core should have been driving the magnetic field to some pretty crazy contortions. As the interior of the planet went through incredible changes, this produced a chaotic, many-lobed field that bears little resemblance to the planetary radiation shield we know and love.

Once the core solidified, Driscoll's model says that the field should have settled downward to a much more than stable dipole. Previously, this was thought to have been the situation for the planet'due south entire history. Now, it seems they have a much more complex history to dig into. All this syncs up quite well with the geological tape, which shows a foreign disturbance in the magnetic field 600-700 millions years ago. According to Discoll's calculations, that's right in the time period nosotros'd expect the Earth to have multiple, oddly space magnetic poles.

ParticleShower

The Earth'southward magnetic field is one reason cosmic rays from the Sun and elsewhere don't cook u.s., and all other life on Earth.

The field of exo-planetology is advancing at a lightning pace, offering an obvious possible path for research into Globe's history. We'll never be able to run across the Earth's bodily past, but astronomers are accruing an ever-growing list of Globe-like planets to study. Somewhen, 1 with fall under their lens at the correct time in its own planetary history to show usa just how we got hither.

In that spirit, there are already efforts at creating a method of measuring the magnetic field of a distant conflicting world — and the true next-gen planet hunting telescopes take still to fifty-fifty go into service. Will we learn that there is a large diversity of ways for a planet to have a magnetic field?

Even in our own solar arrangement, we accept many non-metallic moons with no magnetic field, right alongside Ganeymede, which has a magnetic field so strong it can straight the path of incoming charged particles from space (chosen a magnetosphere). What volition we find in the larger universe could be even more unique and alien, but in a way, we should hope for particularly mundane, Globe-like discoveries.