Earth's magnetic field is an invisible, but crucial barrier that protects Earth from the solar wind – a stream of charged particles emanating from the outer layers of the Sun. The protective properties of the magnetic field may fail due to a process known as magnetic reconnection that occurs when two opposing magnetic field lines break and reconnect, dissipating large amounts of energy and accelerating particles that threaten air traffic and satellite communications systems.
Just before Earth's magnetic field, the onslaught of electrons and ionized gases in the solar wind creates a turbulent wake of magnetic energy, the magnetosheath. While magnetic reconnection near Earth is well documented, physicists have tried to determine whether reconnection will take place in this turbulent zone.
A new research by James Drake, a professor at the University of Maryland, suggests the answer to this question is yes. The observations published in the journal Nature on May 1
"We know that magnetic energy in turbulent systems is getting smaller and smaller." At some point, this energy is completely consumed. The big question is how this happens and what role the magnetic reconnection plays on such small scales, "said Drake." This study shows that a reconnection can actually take place on the electron scale without any ions, suggesting that a reconnection of the
By providing a clearer picture of the physics of magnetic reconnection, The Discovery promises to enhance the understanding of scientists for some unanswered questions in solar physics.For example, the magnetic reconnection of electrons can make one Role in warming the solar corona play – an expansive layer of charged particles that surrounds the sun and reaches temperatures that are a hundred times higher than the visible surface of the sun.This in turn could help, the physics of the solar wind and the nature of turbulent magnetic systems elsewhere in space to explain.
The NASA Magnetospheric Multiscale (MMS) mission collected the data for analysis. In a pyramid formation with a distance of only 4.5 miles between four identical spacecraft, the MMS fly every 30 milliseconds within the pyramid. These high-precision measurements enabled researchers to detect a turbulent, purely magnetic reconnection, a phenomenon that has not previously been observed.
"MMS discovered the electron-magnetic reconnection, a new process that differs from standard magnetic recovery in calmer areas of the world," said Tai Phan, a senior fellow at the Space Sciences Laboratory at the University of California, Berkeley and lead author of the Newspaper. "This finding helps scientists understand how turbulent magnetic fields derive energy throughout the cosmos."
Because turbulent reconnection involves only electrons, it remained hidden from scientists seeking the telltale signature of normal magnetic reconnection: ion beams. Compared to the standard reconnection, where ions' wide jets emit tens of thousands of miles from the reconnection site, a turbulent reconnect ejects narrow electron beams just a few miles wide.
But MMS scientists were able to develop the design of an instrument, the Fast Plasma Investigation, to develop a technique that allows them to read between the lines and gather additional data points to resolve the jets.
"The key event of the paper happens in 45 milliseconds to show you with the regular data," said Amy Rager, a graduate student at the Catholic University of America in Washington, DC, who worked at the NASA Goddard Space Flight Center develop. "Instead, with this method, we can get six to seven data points in that region so we can understand what's going on."
With the new method, MMS scientists hope to be able to sift through existing records to find more of these events and other unexpected discoveries as well.
"There were some surprises in the data," said Drake. "Magnetic reconnection occurs when two magnetic fields point in opposite directions and cancel each other out – in this case, a large surrounding magnetic field survived after annihilation. Frankly, we were surprised that a turbulent reconnection could occur at very small scales Background Magnetic field present . "
Magnetic reconnection takes place throughout the universe, so scientists who learn about it near Earth can be applied to other phenomena. For example, the discovery of a turbulent electron reconnection could help scientists understand the role of the magnetic reconnection when heating the inexplicably hot solar corona – the outer atmosphere of the sun – and accelerate the supersonic solar wind.
NASA's upcoming Parker Solar Probe mission will travel directly to the Sun in the summer of 2018 to investigate these issues – armed with a new understanding of magnetic reconnection near Earth.
University of Maryland
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