The four spacecraft of NASA’s Magnetospheric Multiscale Mission (MMS) have flown through the heart of a magnetic process that controls Earth’s space weather and geomagnetic storms.
The four MMS spacecraft — shown here in an artist’s concept — have made more than 4,000 trips through the boundaries of Earth’s magnetic field. Image credit: NASA / Goddard / Conceptual Image Lab.
The Earth is surrounded by a magnetic bubble, called the magnetosphere, which protects us from harmful radiation from space.
The magnetosphere is defined by magnetic field lines, stretching out into space from the Earth. When these lines come up against field lines in different orientations – for example from the Sun – a process called magnetic reconnection occurs.
Magnetic reconnection is when the field lines clash and rearrange themselves in an explosive reaction.
The process throws out hot jets of particles, allowing them to cross boundaries normally created by the field lines.
In the Earth system, this process plays the key role in causing geomagnetic storms that can disrupt communications systems on the surface and satellites in space. It also leads to the creation of the auroras in the northern and southern hemispheres.
At the heart of magnetic reconnection is an extremely fast reaction that shoots out protons and electrons.
The movement of protons had been observed before, but now spacecraft have been able to capture direct measurements of the movements of the electrons for the first time, according to a team of researchers led by Dr. James Burch of the Southwest Research Institute in San Antonio, Texas.
“Because of the importance of magnetic reconnection in many laboratory and space environments, this result has opened up a new window into this universal process, one that is otherwise poorly understood,” Dr. Burch and co-authors said.
In March 2015, NASA launched four spacecraft as part of the MMS mission, which was designed to perform a high-resolution space experiment on magnetic reconnection at the electron scale.
“MMS is made up of four satellites flown in a precise formation using GPS that keeps them only around 10 km apart,” the scientists explained.
“This allows them to map the evolution of the event as it happens, and to track the small-scale movements of electrons. It is also able to track the electrons much faster than previous satellites.”
“Satellite measurements of electrons have been too slow by a factor of 100 to sample the magnetic reconnection region. The precision and speed of MMS, however, opened up a new window on the Universe, a new ‘microscope’ to see reconnection,” said team member Dr. Tom Moore of NASA’s Goddard Space Flight Center.
“MMS has made more than 4,000 trips through the magnetic boundaries around Earth, each time gathering information about the way the magnetic fields and particles move.”
The team analyzed the MMS data and determined the reconnection process is driven by the electron-scale dynamics.
The results, published in the journal Science, will aid researchers’ understanding of magnetized plasmas, including those in fusion reactors, the solar atmosphere, and magnetospheres of the Earth and other planets.
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J.L. Burch et al. Electron-scale measurements of magnetic reconnection in space. Science, published online May 12, 2016; doi: 10.1126/science.aaf2939
