Confirm a source of the process behind auroras and star formation

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Rapid magnetic reconnection, rapid convergence, separation and explosive fusion of magnetic field lines give rise to northern lights, solar flares and geomagnetic storms that can disrupt mobile phone service and power grids. The phenomenon occurs in the plasma, state of matter composed of free electrons and atomic nuclei, or ions, which accounts for 99% of the visible universe. But it is not yet known whether rapid reconnection can occur in a partially ionized plasma (plasma containing atoms, as well as free electrons and ions).

Researchers at the Princeton Laboratory of Plasma Physics (PPPL) at the Department of Energy (DOE) have developed the first fully kinetic model of plasma particle behavior and discovered that a quick reconnection could actually occur in partially ionized systems. Kinetic models simulate the distribution and velocity of billions of particles, compared to fluid models that treat plasma as a continuous medium rather than a set of individual particles.

"There is a whole class of partially ionized plasmas whose connection to the reconnection has not been well studied," said physicist Jonathan Jara-Almonte, lead author of an article in Letters of physical examination which reports the recent results. "We have now shown that a fast reconnection can occur in partially ionized systems."

For example, research suggests that a fast reconnection in the partially ionized plasma of the solar chromosphere, the region between the sun's surface and the halo-shaped solar corona, could play a role in the development of jet jets. reaction. These flows are a possible source of the solar wind which bounces the hot plasma charged with the Earth's magnetic field.

Important implications

Rapid reconnection in a partially ionized plasma has important implications for the interstellar medium, the vast clouds of gas and dust that fill the cosmos between the stars. The dense, cold regions of the interstellar medium where stars are formed are only very weakly ionized, and rapid reconnection in these regions can help eliminate magnetic fields that prevent star formation.

Understanding when and where rapid reconnection is still an unresolved problem and previous analytical predictions for partially ionized plasmas was based on extrapolation from totally ionized plasmas. New simulations, done on computers at Princeton University, have shown that the transition to a fast reconnection occurs only when the current sheet is much thinner than expected. The results suggest that plasma and heat transport is different in partially ionized plasmas and may change the mode and timing of reconnection.

These results focus on very small scale reconnection, unlike the process that occurs in the solar chromosphere. Nevertheless, the simulation proved to be compatible with reconnection in the upper chromosphere as well as in small scale laboratory experiments.

In the future, Jara-Almonte plans to compare the results of kinetic simulation with those of fluid simulations that dominated previous modeling of partially ionized plasmas. PPPL physicist Hantao Ji, professor of astrophysics at Princeton University; Masaaki Yamada, Principal Investigator of Magnetic Reconnection Experience (MRX) at PPPL; and Will Fox, with Bill Daughton from Los Alamos National Laboratory.

Explore further:
PPPL experiments show remarkable agreement with satellite observations

More information:
J. Jara-Almonte et al., Kinetic Simulations of Magnetic Reconnection in Partially Ionized Plasmas, Letters of physical examination (2019). DOI: 10.1103 / PhysRevLett.122.015101

Journal reference:
Letters of physical examination

Provided by:
Princeton Plasma Physics Laboratory

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