An article published in the journal “Nature” describes the discovery of a new type of magnetic reconnection. A team of researchers used data collected by NASA’s Magnetospheric Multiscale (MMS) space probes to discover this phenomenon occurring in a boundary layer between the supersonic solar wind and the Earth’s magnetic field called magnetosheath. What was called electron magnetic reconnection is very different from the standard phenomenon and converts magnetic energy into high speed electron jets.
The four MMS (Magnetospheric MultiScale) spacecraft, launched in March 2015, flying in a variable formation allowed to detect with a number of instruments the standard magnetic reconnection generated by the interaction between the magnetic field of the Earth and that of the Sun.
Recently, the mission went further allowing to investigate the turbulence inside the magnetosheath. It contains a lot of magnetic energy coming from the solar corona, an extremely hot environment that ejects particles at speeds around 1.6 million km/h (about 1 million mph).
When this solar wind hits the magnetosheath, it slows down dramatically generating a shock wave composed of chaotic plasma. Electrons are the particles most affected by the phenomenon: they move about forty times faster than the ions accelerated by standard magnetic reconnection. This new phenomenon occurs on much smaller scales than those already detected by the MMS space probes.
So far, researchers examined the ions to discover magnetic reconnection events, but in this case electrons are involved, hence the name electron magnetic reconnection. Jonathan Eastwood of the Imperial College of London, one of the authors of the article, explained that according to his team the new phenomenon concerns electrons because they are fast and light while protons are much slower and heavier so they can’t be part of it.
The key event described in the article lasted only 45 milliseconds. The MMS space probes weren’t designed to measure such quick and small-scale events, but they still detected something. To understand more of it, the researchers developed a new way to use the Fast Plasma Investigation instrument, which allowed to collect more data.
In the image (Mary Pat Hrybyk-Keith / NASA’s Goddard Space Flight Center), solar wind is represented by a sort of yellow haze that flows around the Earth’s magnetic field, indicated by the blue lines. In the boundary area in which they collide, the magnetosheath indicated by the small yellow vortices is formed, where the electron magnetic reconnection was detected.
Tai Phan of the University of California at Berkely, lead author of the article, explained that this discovery brings together two important phenomena such as magnetic reconnection and turbulence. He added that this will help scientists understand how turbulent magnetic fields dissipate energy into the cosmos.