Magnetics Business & Technology - May/June 2019 - 16

RESEARCH & DEVELOPMENT

NASA Spacecraft Discover New Magnetic Process in Turbulent Space
they are still too slow to capture turbulent reconnection in action,
which requires observing narrow layers of fast-moving particles
hurled by the recoiling field lines. Compared to standard reconnection, in which broad jets of ions stream out from the site of reconnection, turbulent reconnection ejects narrow jets of electrons
only a couple miles wide.
"The smoking gun evidence is to measure oppositely directed
electron jets at the same time, and the four MMS spacecraft were
lucky to corner the reconnection site and detect both jets", said
Jonathan Eastwood, a lecturer at Imperial College, London, and
a co-author of the paper.

Credits: NASA's Goddard Space Flight Center/Joy Ng

Crucially, MMS scientists were able to leverage the design of
one instrument, the Fast Plasma Investigation, to create a technique to interpolate the data essentially allowing them to read
between the lines and gather extra data points in order to resolve
the jets.

In a new discovery reported in the journal, Nature, scientists
working with NASA's Magnetospheric Multiscale spacecraft
(MMS) have uncovered a new type of magnetic event in our
near-Earth environment by using an innovative technique to
squeeze extra information out of the data.
Magnetic reconnection is one of the most important processes in
the space filled with charged particles known as plasma around
Earth. This fundamental process dissipates magnetic energy and
propels charged particles, both of which contribute to a dynamic
space weather system that scientists want to better understand,
and even someday predict, as we do terrestrial weather. Reconnection occurs when crossed magnetic field lines snap,
explosively flinging away nearby particles at high speeds. The
new discovery found reconnection where it has never been seen
before; in turbulent plasma.
"In the plasma universe, there are two important phenomena:
magnetic reconnection and turbulence," said Tai Phan, a senior
fellow at the University of California, Berkeley, and lead author
on the paper. "This discovery bridges these two processes."
Magnetic reconnection has been observed innumerable times
in the magnetosphere, the magnetic environment around Earth,
but usually under calm conditions. The new event occurred in a
region called the magnetosheath, just outside the outer boundary of the magnetosphere, where the solar wind is extremely
turbulent. Previously, scientists didn't know if reconnection even
could occur there, as the plasma is highly chaotic in that region.
MMS found it does, but on scales much smaller than previous
spacecraft could probe.
MMS uses four identical spacecraft flying in a pyramid formation
to study magnetic reconnection around Earth in three dimensions. Because the spacecraft fly incredibly close together at
an average separation of just four and a half miles, they hold
the record for closest separation of any multi-spacecraft formation They are now able to observe phenomena no one has seen
before. Furthermore, MMS's instruments are designed to capture
data at speeds a hundred times faster than previous missions.
Even though the instruments aboard MMS are incredibly fast,

Magnetics Business & Technology * May/June 2019

"The key event of the paper happens in only 45 milliseconds.
This would be one data point with the basic data," said Amy
Rager, a graduate student at NASA's Goddard Space Flight
Center in Greenbelt, Maryland, and the scientist who developed
the technique. "But instead we can get six to seven data points
in that region with this method, allowing us to understand what is
happening."
With the new method, the MMS scientists are hopeful they
can come back through existing datasets to find more of these
events, and potentially other unexpected discoveries as well.
For more information, visit: https://www.nasa.gov/

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Magnetics Business & Technology - May/June 2019

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