by The Earth’s magnetic field plays an important role in protecting people from dangerous radiation and geomagnetic activity that could affect satellite communications and the operation of electrical grids. And it moves.
Scientists have studied and tracked the movement of magnetic poles for centuries. The historical movement of these poles indicates a change in the global geometry of the Earth’s magnetic field. It may even indicate the beginning of a field reversal: a “shift” between the north and south magnetic poles.
I am a physicist who studies the interaction between planets and space. While the magnetic north pole moving a little is no big deal, a reversal could have a big impact on Earth’s climate and our modern technology. But these changes do not occur instantly. Rather, they occur over thousands of years.
Magnetic field generation
So how are magnetic fields like the one around the Earth generated?
Magnetic fields are generated by moving electric charges. A material that allows charges to move easily in it is called a conductor. Metal is an example of a conductor: people use it to transfer electrical currents from one place to another. The electric current itself is simply negative charges called electrons moving through the metal. This current generates a magnetic field.
Layers of conductive material can be found in Earth’s liquid iron core. Charging currents move throughout the core and liquid iron also moves and circulates in the core. These movements generate the magnetic field.
Earth is not the only planet with a magnetic field: gas giant planets like Jupiter have a conductive layer of metallic hydrogen that generates their magnetic fields.
The movement of these conductive layers within the planets results in two types of fields. Larger motions, such as large-scale rotations with the planet, lead to a symmetrical magnetic field with a north pole and a south pole, similar to a toy magnet.
These conductive layers may have some local irregular motions due to local turbulence or smaller flows that do not follow the large-scale pattern. These irregularities will manifest themselves in some small anomalies in the planet’s magnetic field or in places where the field deviates from being a perfect dipole field.
These small-scale deviations in the magnetic field can actually lead to large-scale field changes over time and potentially even a complete reversal of the polarity of the dipole field, where north becomes south and vice versa. The “north” and “south” designations in the magnetic field refer to their opposite polarities; They are not related to geographic north and south.
Earth’s magnetosphere, a protective bubble
Earth’s magnetic field creates a magnetic “bubble” called the magnetosphere above the uppermost part of the atmosphere, the ionosphere layer.
The magnetosphere plays an important role in protecting people. It shields and deflects harmful high-energy cosmic ray radiation, which is created in stellar explosions and constantly moves through the universe. The magnetosphere also interacts with the solar wind, which is a flow of magnetized gas sent from the Sun.
The interaction of the magnetosphere and ionosphere with the magnetized solar wind creates what scientists call space weather. The solar wind is generally mild and there is little or no space weather.
However, there are times when the Sun spews large magnetized clouds of gas into space called coronal mass ejections. If these coronal mass ejections reach Earth, their interaction with the magnetosphere can generate geomagnetic storms. Geomagnetic storms can create auroras, which occur when a stream of energized particles hits the atmosphere and lights up.
During space weather events, there is more dangerous radiation near Earth. This radiation can potentially harm satellites and astronauts. Space weather can also damage large conducting systems, such as large oil pipelines and power grids, by overloading currents in these systems.
Space weather events can also disrupt satellite communications and GPS performance, on which many people depend.
field flips
Scientists map and track the general shape and orientation of Earth’s magnetic field using local measurements of the field’s orientation and magnitude and, more recently, models.
The location of the north magnetic pole has moved approximately 600 miles (965 kilometers) since the first measurement was taken in 1831. The speed of migration has increased from 10 miles per year to 34 miles per year (16 km to 54 km) in more recent years. This acceleration could indicate the beginning of a field reversal, but scientists can’t really tell with less than 200 years of data.
The Earth’s magnetic field reverses on time scales ranging from 100,000 to 1,000,000 years. Scientists can tell how often the magnetic field reverses by looking at volcanic rocks in the ocean.
These rocks capture the orientation and strength of Earth’s magnetic field when they are created, so dating them provides a good picture of how Earth’s field has evolved over time.
Field inversions occur quickly from a geological point of view, although slow from a human perspective. A reversal usually takes a few thousand years, but during this time the orientation of the magnetosphere can change and expose more of the Earth to cosmic radiation. These events can change the concentration of ozone in the atmosphere.
Scientists can’t say for sure when the next field reversal will occur, but we can continue to map and track the movement of Earth’s magnetic north.
This article is republished from The Conversation, an independent, nonprofit news organization bringing you data and analysis to help you understand our complex world.
It was written by: Ofer Cohen, University of Massachusetts Lowell.
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Ofer Cohen works for the University of Massachusetts Lowell. The university benefits from any public article written by one of its professors in terms of exposure and visibility. Ofer Cohen received funding from NASA that is somehow related to the article.
