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Tom Moore: Magnetic reconnection is the process of disconnecting or connecting
the magnetic fields to each other, directing energy into the Earth on the dayside
and then letting it go on the nightside. The interplay between the
2 is what produces all the space weather around the Earth that
has big effects, can damage our spacecraft, can
hurt astronauts, can upset the flow of electrical energy in our electric grid
on the surface of the Earth. MMS is a mission with 4 spacecraft
that travel in formation, in an orbit that takes them
out into 2 special places near the Earth,
one upstream toward the sun, one downstream away from the sun.
Both of those place have magnetic reconnection.
We have never before MMS had the ability to
essentially run the camera fast enough to catch it
as it goes by, to make many measurements per second.
The science payload for MMS is all mounted on a single deck plate.
It consists of some 25 boxes per spacecraft,
divided into 3 general groups of instruments. That's those measuring
fields (electric and magnetic), those for measuring plasmas,
and a third for measuring energetic particles.
The magnetic field sensors are out on arms that extend away from the spacecraft. They are fixed, but the spacecraft is
spinning slowly, about once every 20 seconds.
The electric field is quite a bit different. It consists of 4 wires
that extend out away from the spacecraft with a ball out on the end of each of them.
that actually contacts the plasma.
All 4 of those are spinning around with the spacecraft with this 20 second period.
And then there's a third axis, there's booms that extend along
the spin axis of the spacecraft, both upward and downward with the probe at the end.
So you've got 3 components of the electric field. They can measure everything from
up to small wiggles and vibrations of the electric field.
Another sensor is called the search coil magnetometer is just a loop of wire
connected to a suitable amplifier, and it is designed
to measure the fluctuations at higher frequencies than you could get
with the DC magnetometers. For the plasmas
8 boxes. 2 boxes at each of the 4 points of the compass on the spacecraft.
Those are equally spaced all around the spacecraft. That is a real
key ingredient for being able to see the
entire sky instantaneously, without waiting for the spacecraft to spin
Then there is also the hot plasma composition analyzer
1 per spacecraft. It has sensor head that looks all around in a
360 degree annulus that sticks out the side of the spacecraft
and sweeps out the whole sky twice per spin.
It measures the chemical species of the particles.
Next are the accelerated particle analyzers that are measuring much more energetic particles
that are accelerated by the reconnection process.
Ultimately, what we will be doing is comparing our observations with simulations of the entire magnetoshere
as it is influenced with the solar wind coming in, down to the
details of what reconnection is occurring. People who do
those simulations try to apply them to all other kinds of places, like in the solar
atmosphere and other astrophysical stars
and other objects. They are very interested in
whether those simulations are accurate and reflect reality well
This is going to be the first time we actually bump them up against hard data of what's going
in there. I am almost certain, I'm very certain, they are gonna learn something
from that and the simulations will get better.
We are going to measure things at rates that have never been done before, in places that
have been hard to reach and even see, because they go by to fast
so, it's going to be fantastic.
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