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Studying Earth’s Magnetic Personality
Presented by Science NASA.
Magnetic reconnection could be the Universe's favorite way
to make things explode.
It operates anywhere magnetic fields pervade space -
which is to say almost everywhere.
In the cores of galaxies, magnetic reconnection sparks
explosions visible billions of light-years away.
On the sun, it causes solar flares as powerful as a million
atomic bombs.
At Earth, it powers magnetic storms and auroras.
It's ubiquitous.
The problem is, researchers can't explain it.
The basics are clear enough.
Magnetic lines of force cross, cancel, reconnect and—Bang!
Magnetic energy is unleashed, with charged-particles flying
off near the speed of light.
But how?
How does the simple act of crisscrossing magnetic field
lines trigger such a ferocious explosion?
"Something very interesting and fundamental is going on
that we don't fully understand," says Jim Burch of the
Southwest Research Institute.
NASA is about to launch a mission to get to the bottom of
the mystery.
It's called MMS, short for "Magnetospheric Multiscale" and
it consists of four spacecraft that will fly through
Earth's magnetic field, or "magnetosphere," to study
reconnection in action.
"Earth's magnetosphere is a wonderful natural laboratory
for studying this phenomenon," says Burch, the MMS
Principal Investigator.
Slated for launch on March 12th, the four spacecraft were
designed, built and tested at NASA’s
Goddard Space Flight Center.
Each one is shaped like a giant hockey puck, about 4 meters
in diameter and 1 meter in height.
In space, however, they are much larger.
"After launch, the spinning spacecraft will unfurl their
electromagnetic sensors, which are at the end of wire booms
as much as 60 meters long," says Craig Tooley,
MMS Project Manager at Goddard.
"When fully extended, the sensors are as wide as a baseball
field." These sprawling, spinning probes will fly in
precise formation, as close as 10 kilometers apart and are
guided by GPS satellites orbiting Earth far below them.
"We can maintain formation with an accuracy
of only 100 meters," says Tooley.
"This is crucial to our measurements." Any new physics MMS
observes could help provide clean energy on Earth.
"For many years, researchers have looked to fusion as a
clean and abundant source of energy for our planet,"
says Burch.
"One approach, magnetic confinement fusion, has yielded
very promising results with devices such as tokamaks.
But there have been problems keeping the plasma contained
in the chamber." "One of the main problems is magnetic
reconnection," he continues.
"A spectacular result of reconnection is known as the
'sawtooth crash.' As heat in the tokamak builds up, the
electron temperature reaches a peak, then 'crashes' to a
lower value.
Some of the hot plasma escapes.
This is caused by reconnection of the containment field."
In light of this, you might suppose that fusion chambers
would be a good place to study reconnection.
But no, says Burch.
Reconnection in tokamaks happens in a tiny volume only a
few centimeters wide.
It is practically impossible to build sensors small enough
to probe the reconnection zone.
Earth's magnetosphere is much better.
In the expansive magnetic bubble that surrounds our planet,
the process plays out over volumes as large as tens of
kilometers across, for instance, when reconnection at the
sun propels plasma clouds toward Earth, where additional
reconnection events then sparks auroras.
"We can fly spacecraft in and around it and get a good look
at what's going on," he says.
That is what MMS will do: fly directly into the
reconnection zone.
The spacecraft are sturdy enough to withstand the
energetics of reconnection events known to occur in Earth's
magnetosphere, so there is nothing standing in the way of a
full two-year mission of discovery.
For explosive updates, stay tuned to science.nasa.gov.