Terrestrial near space, explosive bursts of plasma from the solar wind are observed daily. Major eruptions are indicated by, among other things, the sudden brightening of the aurora borealis.
The physics associated with the eruptions cause the strongest magnetic disturbances, which can affect, for example, the operation of electricity networks, says the professor of space physics at the University of Helsinki Minna Palmroth.
The studied plasma eruptions are told when the arc of the Aurora Borealis rises suddenly towards the sky. Then the arc brightens and different shapes suddenly appear.
Eruptions related to these so-called substorms have now been modeled at the Physics Department of the University of Helsinki.
Solar wind consists of charged particles falling from our nearby star and orbiting the Earth’s magnetosphere. Plasma eruptions are generated on the night side of the Earth by the interaction of the solar wind and the magnetosphere.
Eruptions are difficult to predict and vary in intensity. The chain leading to the eruptions has been the unsolved questions of space physics. Attempts have been made to find a solution to it since the 1960s, Palmroth points out the university in the bulletin.
The space physics group at the University of Helsinki studies eruptions using their Vlasiator model. Vlasiator modeling requires the computing power of a supercomputer. The software was developed for more than ten years.
Modeling showed that the main theories about the origin of eruptions are correct.
The first explanation has been that the so-called magnetic reconnection disconnects the plasma discharge from the magnetic field.
“Energy is constantly transferred from the solar wind to the magnetic field. In a substorm, energy accumulates in the magnetic field and stretches it at night like a windbag. At some point, a part of the magnetic field comes off as a large plasma cloud, or plasmoid,” says Palmroth.
The same can be described as the energy of the solar wind increases in the magnetic field in the same way as water slowly trickles out of a faucet. The water accumulates as a drop, until at an unpredictable moment the drop falls.
“Approximately this is how it happens in the magnetic field as well. Magnetic energy accumulates in its tail, and in one moment a part of the magnetic ring detaches.”
Another explanation has been that the kinetic instabilities break the current sheet that maintains the tail of the Earth’s magnetosphere, leading to plasma detachment. A small disturbance therefore grows into a large wave, which can then break the magnetic system.
“Now it seems that the cause-and-effect relationships are indeed more complicated than previously understood,” says Palmroth.
Result according to him, helps to understand how plasma eruptions in the earth’s magnetic field can arise.
It helps the design of spacecraft and equipment used in space and improves the predictability of so-called space weather.
What was new was that the Earth’s near space was modeled in six dimensions and on a scale corresponding to the size of the magnetosphere. What does it mean in six dimensions?
“In order to accurately model the plasma, in addition to the three spatial dimensions, the velocity distributions of the particles in the three-dimensional velocity space must be modeled. So a total of three dimensions of place and three dimensions of speed space”, answers Palmroth.
“If you don’t model this velocity space, you can’t accurately model all the physics involved in eruptions, and that’s why previous models haven’t gotten the same answers.”
The study was published Nature Geoscience –in the scientific journal.
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