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  • PPPL provides insight to how magnetic reconnection energizes plasma particles

PPPL provides insight to how magnetic reconnection energizes plasma particles

The process of magnetic field line reconnection, in which the magnetic field lines in a plasma snap apart and violently reconnect, transforms magnetic field energy into particle energy. Little was known about this phenomenon that is known most prominently in the form of solar flares on the surface of the sun. The subsequent geomagnetic storms on earth have demonstrated how much energy can be released by magnetic reconnection.

In the research conducted on the Magnetic Reconnection Experiment (MRX) at PPPL, scientists measured experimentally the amount of magnetic energy that turns into particle energy. They showed that reconnection converts about 50 percent of the magnetic energy in the plasma, with one-third of the conversion heating the electrons and two-thirds accelerating the ions.

The findings also suggested the process by which the energy conversion occurs. According to the researchers, reconnection first propels and energizes the electrons, which creates an electrically charged field that becomes the primary energy source for the ions.

Magnetic Islands and Magnetic Reconnection
On a much smaller scale than in astrophysics, the phenomenon of magnetic reconnection comes in play with magnetic islands in magnetically confined fusion plasmas. In Magnetic islands are structures that attribute their name to the islands-like appearance in a cross-section of the magnetic flux surface (see illustration). In three dimensions, the structure extends to a tube that circulates the entire plasma (multiple times) and closes in on itself.

Associated with magnetic islands are short-circuits of radial heat transport towards the plasma edge, which may cause violent disruptions. On the other hand, the islands could be used to induce transport of waste products such as helium ash. Various side-effects of magnetic islands and its influence on the performance of a reactor, make it an ever recurring topic in fusion research.

It is the hope therefore, that these findings of PPPL on magnetic reconnection provide not only valuable insights at the scales of astrophysics but can also lead to new insights in suppression and control of magnetic islands in fusion reactors.