Experiment Demonstrates How Electron Pressure Accelerates Magnetic Reconnection

Magnetic reconnection, a phenomenon wherein oppositely directed magnetic field lines in plasma can break apart and reconnect, is still very poorly understood. This is despite the fact that it is believed to play a crucial role in the creation of auroras on Earth, flares on the surface of the sun, and even in processes taking place in the vicinity of black holes and neutron stars.

Physicists associated with the Magnetic Reconnection Experiment at the Princeton Plasma Physics Laboratory (PPPL) have now provided an answer to why magnetic reconnection seems to occur much faster than theory says it should. The experiment, whose findings have been detailed in a study published in the latest edition of Physical Review Letters, reveals that electrons that exert a varying degree of pressure along the magnetic field lines undergoing reconnection enable fast reconnection.

“The main issue we addressed is how reconnection can take place so quickly,” study lead author Will Fox, a physicist at PPPL, said in a statement released Friday. “The experiments demonstrate how the plasma can sustain a large electric field while preventing a large electric current from building up and halting the reconnection process.”

Reconnection occurs wherever plasma is present, which is 99 percent of the universe. Under normal conditions, the magnetic field lines inside plasmas don't break or merge, but occasionally, when these field lines get close to each other, the entire configuration changes, releasing, in the process, massive bursts of energy.

According to the study, the variation in electron pressure balances and keeps a strong electric current inside the plasma from growing out of control and halting reconnection. This, in turn, speeds up the process.

In addition to furthering our understanding of the esoteric processes taking place in areas surrounding black holes, studying the causes of magnetic reconnection could also help scientists develop better models for predicting space weather phenomenon that can pose a serious threat to satellites and manned missions.

“Magnetic reconnection in the magnetosphere, the magnetic field that surrounds the Earth, can set off geomagnetic ‘substorms’ that disable communications and global positioning satellites (GPS) and disrupt electrical grids,” PPPL said in the statement. “Improved understanding of fast reconnection can help locate regions where the process triggering storms is ready to take place.”