Earth’s magnetic field is 3.5 billion years old, and since then, it has shielded every life form on Earth from the sun’s harmful cosmic radiation. The Earth’s magnetic field was studied in 1600 by William Gilbert in England. The magnetic field of the Earth’s magnetosphere is similar to a bar magnet. But the field lines are far from Earth and bend away. This is due to the ionized solar wind from the Sun that encounters the Earth.
Earth’s magnetosphere acts as a shield that protects it from the energetic solar wind. It extends more than five times the distance to the moon. The source of Earth’s magnetism is still not completely understood. Most investigators attribute the field to convection currents within Earth’s interior.
The direction and strength of Earth’s magnetic field change over time. The magnetic field can be deformed when all the other charged particles generate electric and magnetic fields. The charged particles that are accelerated to higher energies can hit communication satellites.
What is the magnetosphere?
The magnetosphere is the region around a planet, including Earth, influenced by its magnetic field. It is a protective shield formed by the interaction between the planet’s magnetic field and the solar wind—a stream of charged particles, mostly electrons and protons, emitted by the Sun.
Key features and functions of the Earth’s magnetosphere include:
Magnetic Field: The Earth has a dipole magnetic field, with a north magnetic pole near the geographic South Pole and a south magnetic pole near the geographic North Pole. The magnetic field lines extend from the planet’s interior into space, forming a magnetic field that envelops the Earth.
Bow Shock: As the solar wind approaches the Earth, the magnetic field deflects the charged particles, creating a boundary called the bow shock. The bow shock marks the outermost edge of the magnetosphere and acts as a barrier against the direct impact of the solar wind.
Magnetopause: Inside the bow shock, the magnetosphere’s boundary with the solar wind is called magnetopause. Magnetopause is where the pressure from the solar wind and the pressure from the Earth’s magnetic field balance.
Magnetotail: Extending away from the Earth in the opposite direction of the Sun, the magnetotail is a long, comet-like tail formed by the stretching and elongation of the magnetosphere due to the solar wind. It can extend millions of kilometers into space.
Van Allen Radiation Belts: Within the magnetosphere are two regions known as the Van Allen radiation belts. These belts are charged particles trapped by the Earth’s magnetic field. The inner belt primarily comprises energetic protons, while the outer belt contains protons and electrons.
Plasma is ionized gas, and because the charges move, they generate currents. Those currents generate magnetic fields. The magnetosphere is the extended magnetic field that is from the Earth. Then is deformed greatly through interaction with the plasma that comes from the sun. It’s called the solar wind, which deforms the earth’s magnetosphere into a long tail like a comet’s tail.
Earth’s magnetic pole is located where the magnetic field lines are perpendicular to Earth’s surface. However, it’s a complicated and rather dynamic planet because of this. The magnetic poles are not necessarily fixed at the same location. They tend to wander.
Over the past few centuries, the northern magnetic pole has slowly moved from Arctic Canada to northern Siberia. The magnetic field lines along Earth’s surface don’t always point to the magnetic poles. The geomagnetic poles are not currently aligned with the geographic poles.
- The major region in the magnetosphere is the Van Allen Belts. In these regions, electrons and protons travel at very high speeds.
So this extends outside of Earth. It affects electrically charged particles, also called ions. Magnetopause is the accidental boundary between the surrounding plasma and the magnetosphere.
Temperature: The temperatures range from 6000 kelvin to 35,100 kelvin (10,340 to 62,720 degrees Fahrenheit). It is very hot compared to the temperatures of Earth.
Length: It extends approximately 65,000 kilometers area. The planetary distance from the magnetosphere to the solar wind pressure is the Chapman–Ferraro distance.
Composition: It contains plasma, electrically charged particles in equal proportions of positive charge on ions and negative charge on electrons. Sun is the main source of plasma in the solar system.
Structure: Plasma, momentum, magnetic dipole, object’s spin nature, the magnitude and direction of the solar wind flow.
What causes a magnetic field?
An electric current causes a magnetic field. Four earth layers are the inner core, outer core, mantle, and crust. The inner and outer core is iron because iron is a good conductor. Iron atoms form metallic bonds where the electrons are shared between atoms and move freely in an electron sea.
These moving electrons can create a magnetic field. The solid inner core heats the lower part of the liquid outer core. It causes convection currents. A hot, less dense molten mass moves upward while a cooler, more dense mass sinks to the bottom of the outer core. These moving iron electrons generate a current, generating Earth’s magnetic field.
There’s a process on Earth called the Coriolis effect. It is what determines the major wind directions on Earth. Its directionality also controls motion deep in the Earth. In combination with the convection currents, a spiraling effect occurs. Because of this spiral, all the individual magnetic fields align and create one big magnetic field. This is why Earth has a magnetic field!
- A major difference between Earth’s magnetic field and a bar magnet’s is that the Earth’s magnetic field changes in direction over time.
How much does the Earth’s magnetic field move? A lot! The Earth’s magnetic poles flip about four to five times every million years. It’s estimated that a full pole flip only takes several thousand years. All of Earth’s past magnetic field orientations are imprinted in the Earth’s crust.
A new crust is formed at mid-ocean ridges on the seafloor, where two tectonic plates pull apart and lava wells up between them. As the lava cools, it forms tiny magnetic mineral grains. As these minerals cool, they become small magnets aligned with Earth’s magnetic field. This magnetic fingerprint is locked into the crust when it solidifies and can stay there long.
How does this prove that the poles flipped? People have measured the magnetism of the crust at mid-ocean ridges. They have found that the magnetism in the rocks switches back and forth, forming a symmetrical zebra-striped pattern. Some scientists think we might see another pole reversal soon since the North Pole has been wandering towards Siberia recently.
How is the magnetosphere formed?
The magnetic field is generated deep down in the Earth’s core. A dynamo effect causes Earth’s magnetic field or magnetosphere. Earth’s outer core is the liquid metal, and fluid motion generates electric currents.
- The motion of the fluid is sustained by convection and driven by buoyancy.
When the Earth spins on its axis, the electric currents form a magnetic field that extends around the planet. If the whole mass of the earth were solid, there wouldn’t be much of an electric field.
A similar example of the dynamo effect is the dynamo light. When you pedal, the dynamo’s bike magnets start spinning, creating an electric current. It turns on the light. The Wang Sheeley Arge Enlil model shows high or lower-speed solar wind coming to Earth.
The Geospace model tells about magnetic variations in the vicinity of Earth. Those magnetic variations can cause geoelectric fields. Those geoelectric fields can drive currents and power lines and disrupt power grids.
Why is the magnetosphere important?
The sun is a magnet that spits charged particles that travel to the Earth like the solar wind. Now the thing is, the Earth is also a magnet. When that solar wind arrives at the Earth, the charged particles from the sun interact with the Earth’s magnetic field.
The magnetosphere is a protective field around the Earth, shielding the solar wind constantly streaming toward Earth. Typically, the solar wind moves supersonically at about 400 kilometers per second. The solar wind primarily comprises protons and electrons-charged particles streaming from the Sun. Some of those particles have very high energies radiation energies. They can damage astronauts and spacecraft.
- The solar wind would blow the atmosphere away, and liquid water could not exist on the surface without an atmosphere. So, It is the magnetosphere that protects the Earth from this damage.
The radiation coming from outer space would damage any life on Earth. It can cause mutations in the DNA and all sorts of nasty things. So magnetosphere helps to protect it and keep the atmosphere safe.
“Magnetospheres.” NASA Science. NASA.
Ratcliffe, John Ashworth. An Introduction to the Ionosphere and Magnetosphere. CUP Archive. ISBN 9780521083416.
“Ionosphere and magnetosphere.” Encyclopædia Britannica.
Van Allen, James Alfred. Origins of Magnetospheric Physics. Iowa City, Iowa USA: University of Iowa Press.
Table of Contents