This artist’s depiction illustrates the four Magnetospheric Multiscale (MMS) spacecraft flying in a tetrahedral formation, superposed on a conceptual rendering of Earth’s magnetosphere (not to scale). MMS is measuring this explosive physical process as the Sun’s and Earth’s magnetic fields interact, converting stored magnetic energy into kinetic energy and heat.
Image Courtesy of NASA's Goddard Space Flight Center Conceptual Image Lab
Last October the MMS mission, made of 4 identical satellites flying in a precise formation 10 km apart, flew through the heart of a magnetic reconnection region, on the boundary between the solar wind and Earth's magnetosphere. In only a few seconds, MMS collected hundreds of observations of the way the magnetic fields and particles were moving. Examining the data from the encounter, the MMS team saw a drop in the magnetic field to near zero, oppositely directed ion flows, accelerated electrons, an enhanced electric field, and a strong electrical current. The tell-tale signature of reconnection, however, was a spike observed in the electric power generated by the electrons. This was the 'smoking gun' for reconnection. It was theoretically predicted but never seen until MMS.
The solar wind and Earth's magnetospheric plasmas are both magnetized. For reconnection to occur, the plasmas become ‘demagnetized’ - that is, the plasma and the magnetic field become decoupled. The critical and final stage in this process occurs in a relatively small region in space known as the ‘electron dissipation region.’ As the electrons become demagnetized, the magnetic fields of the Sun and the Earth interconnect and the solar wind and magnetospheric plasmas mix.
One of the mysteries of Magnetic Reconnection is why it’s explosive in some cases, steady in others, and in some cases, Magnetic Reconnection doesn’t occur at all. Whether explosive or steady, the local particles are caught up in the event, hurled off to areas far away, crossing magnetic boundaries they could never have crossed otherwise. At the edges of Earth's magnetic environment, the magnetosphere, such events allow solar radiation to enter near-Earth space.
The data obtained by MMS shows that Magnetic Reconnection is dominated by the physics of electrons — thus providing crucial information about what powers this fundamental process in nature. These discoveries - which have significant implications for space and solar physics, astrophysics, and fundamental plasma physics - were published in the May 12 online issue of Science.
Source: Southwest Research Institute: http://www.swri.org/9what/releases/2016/mms-magnetic-reconnection.htm#.Vz-6dL6DtsS