Simulation of the Earth’s magnetosphere in the laboratory

(ORDO NEWS) — The magnetosphere forms around any magnetized object, such as a planet, that is immersed in a stream of ionized gas called plasma.

Because the Earth has its own magnetic field, it is surrounded by a large magnetosphere that extends into space, blocks deadly cosmic rays and particles from the Sun and stars, and allows life itself to exist.

In the journal Physics of Plasmas, scientists from Princeton, the University of California and the ETH in Portugal report a laboratory method for studying smaller magnetospheres, sometimes only a millimeter thick.

These mini magnetospheres have been observed around comets and near certain regions of the Moon, and it has been suggested that they could power spacecraft. They are good test benches for studying magnetospheres of large planetary sizes.

Previously, laboratory experiments have been carried out using plasma wind tunnels or high-energy lasers to create mini-magnetospheres.

However, these early experiments were limited to one-dimensional measurements of magnetic fields, which do not represent the full three-dimensional behavior that scientists need to understand.

“To overcome these limitations, we have developed a new experimental mini-magnetosphere platform at the University of California’s Large Plasma Device (LAPD),” says author Derek Schaeffer.

This platform combines the LAPD’s magnetic field with a laser-driven fast plasma and a current-driven dipole magnet.

The LAPD magnetic field provides a model of the solar system’s interplanetary magnetic field, while the laser-guided plasma models the solar wind, and the dipole magnet provides a model of the Earth’s own magnetic field. Motorized probes allow the system to be scanned in three dimensions, combining data from tens of thousands of laser shots.

The advantage of using this setup is that the magnetic field and other parameters can be carefully changed and controlled.

If you turn off the dipole magnet, all signs of the magnetosphere disappear. When the dipole’s magnetic field is turned on, the magnetopause can be detected, which is a key piece of evidence for the formation of the magnetosphere.

The magnetopause is the place in the magnetosphere where the pressure of the planetary magnetic field is precisely balanced by the solar wind. Experiments have shown that as the dipole magnetic field increases, the magnetopause becomes larger and stronger.

The effect on the magnetopause was predicted by computer simulations, which were carried out by the researchers to better understand and validate the experimental results. These simulations will also guide future experiments, including studies using the recently installed cathode at LAPD.

“The new cathode will provide faster plasma streams, which in turn will allow us to study the nose impacts seen around many planets,” Schaeffer said.

Other experiments will study magnetic reconnection, an important process in Earth’s magnetosphere in which magnetic fields annihilate, releasing tremendous energy.

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