By flying spacecraft through the magnetic fields that connect the Earth to the Sun, researchers at NASA’s Goddard Space Flight Center in Maryland have seen for the first time seen the inside of an explosive, invisible burst of energy known as a magnetic reconnection event.
As scientists at the US space agency explained Thursday in a statement, magnetic reconnection is one of the primary sources of space radiation, and learning more about these events would not only shed new light on the environment surrounding our little planet, but it would also help keep our astronauts and are spacecraft safer as we prepare to embark on longer-distance flights.
Despite being a far better vacuum than can be created on Earth, space is home to many small particles and is extremely active. It “overflows with energy” and is home to “a complex system of magnetic fields,” NASA said. On occasion, two sets of magnetic fields connect, which causes an “explosive” reaction to occur in the form of a magnetic reconnection. As these fields re-align, they convert magnetic energy into the heat and kinetic energy of charged particles.
Now, for the first time, the Goddard team has used the four Magnetospheric Multiscale (MMS) spacecraft to observe what happens inside a magnetic reconnection event, and as they reported in the latest edition of the journal Science, they not only observed magnetic energy being converted into particle energy, but also measured the electrical field and current, and found that the process is dominated by the physics of electrons.
Getting to the heart of a long-standing puzzle
While the effects of magnetic reconnection have been observed throughout the solar system in various forms, scientists were never able to directly witness the phenomenon prior to the MMS mission, which according to lead author Jim Burch of the Southwest Research Institute (SwRI) in San Antonio, is the first satellite with “the precision needed” to collect such data.
The MMS mission is comprised of four identical probes that launched in March 2015 and fly in a pyramid-shaped formation to create a 3D map of anything they observe. Last October, the probes traveled through a magnetic reconnection event which took place at the point where the magnetic fields of the Earth and sun meet. Though the encounter was short-lived, lasting just 25 seconds, it enabled the MMS spacecraft to make thousands of previously-impossible observations.
“From previous satellites’ measurements, we know that the magnetic fields act like a slingshot, sending the protons accelerating out,” Burch explained. “The decades-old mystery is what do the electrons do, and how do the two magnetic fields interconnect. Satellite measurements of electrons have been too slow by a factor of 100 to sample the magnetic reconnection region. The precision and speed of the MMS measurements, however, opened up a new window on the universe, a new ‘microscope’ to see reconnection.”
The four MMS spacecraft flew across the boundary of the magnetosphere and directly through a portion of the phenomenon known as the dissipation region, where the reconnection itself occurs. The observations reveal that, as the magnetic fields shifted suddenly, electrons were fired off in straight lines at speeds of several hundred miles per second – fast enough for them to cross over the magnetic boundaries rather than being deflected backwards.
Observations found to match the crescent model simulation
Once they made it across, the particles were affected by the new magnetic fields and made a U-turn in accordance with a computer simulation known as the crescent model. Then, much to the surprise of the NASA team, these crescents made an abrupt turn at the moment that the magnetic field lines of the Earth and sun interconnected.
The data revealed that the process was “orderly and elegant,” said Goddard scientist Michael Hesse, the man who originally developed the crescent model. “There doesn’t seem to be much turbulence present, or at least not enough to disrupt or complicate the process.”
Observing the crescent shape in the particle distribution “shows us that the electrons move in such a way that electric fields are established and these electric fields in turn produce a flash conversion of magnetic energy,” said co-author Roy Torbert, a scientist with the University of New Hampshire’s Space Science Center (SSC). “The encounter that our instruments were able to measure gave us a clearer view of an explosive reconnection energy release and the role played by electron physics.”
Since October, MMS has flown through five additional magnetic reconnections, and it is hoped that these observations will provide even more information about the processes that drive these unusual phenomenon. Each set of observations made by the spacecraft should help explain each component of these high-energy events, NASA explained, and this knowledge will help experts map out the space environment and better prepare for the long-distance journeys ahead.
Image credit: NASA Goddard