For the First Time, Spacecraft Measured an Explosive Magnetic Phenomenon

May 12, 2016 | Joanne Kennell

Artist's rendition of the four MMS spacecraft orbiting Earth and its magnetic field.
Photo credit: NASA

This is a critical step in understanding space weather.

Earth’s magnetic field is everybit as essential to life as the air we breath, the water we drink, and the sunlight that keeps us warm. Although we can’t see, hear, or touch it, the magnetosphere provides a crucial barrier between us and the sun’s magnetic field, which often drives streams of charged particles — known as the solar wind — towards Earth.

The interaction between Earth’s magnetic field and the sun’s can cause intense space storms, which have been known to temporarily knock out satellites.

A new study, which will appear in the May 13 issue of the journal Science, provides the first major results of NASA’s Magnetospheric Multiscale (MMS) mission, including a never-before-seen look at the interaction between the magnetic fields of Earth and the sun.

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The paper describes the first direct and detailed observation of a phenomenon known as magnetic reconnection, which occurs when two clashing magnetic field lines break and reconnect with each other, releasing huge amounts of energy.

To make the process of magnetic reconnection easier to understand, James Drake, a professor of physics at UMD and co-author of the study, used this analogy in a press release:

"Imagine two trains traveling toward each other on separate tracks, but the trains are switched to the same track at the last minute. Each track represents a magnetic field line from one of the two interacting magnetic fields, while the track switch represents a reconnection event. The resulting crash sends energy out from the reconnection point like a slingshot."

Although researchers have tried to study magnetic reconnection in the lab and space for almost 50 years, the MMS mission is the first to directly observe how reconnection happens.

Four identical spacecraft flying in a pyramid formation at the edge of Earth’s magnetic field, with as little as 10 kilometers (6.2 miles) of distance between them, imaged electrons in the pyramid once every 30 milliseconds — generating 100 times greater resolution than previous efforts.

NASA's MMS spacecraft orbiting in pyramid formation

The four MMS spacecraft in a pyramid shape that can be re-scaled by changing the distances between each spacecraft. Photo credit: NASA GSFC

Here is what MMS captured: Electrons shoot away in straight lines from the reconnection event at hundreds of miles per second and travel across magnetic boundaries that would normally deflect them. But once they crossed the boundary, the particles curved back around in response to the new magnetic field lines they encountered, making a U-turn.

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"There have been theories about the movement of electrons in magnetic reconnection for decades, but this is the first real proof of what they do. We have known what should be there — but knowing and actually measuring are two very different things," said Jonathan Eastwood from Imperial's Department of Physics, in a separate press release.

Although observing reconnection in detail is a major milestone, the ultimate goal of MMS is to determine how the magnetic field lines break initially.

Measuring the behavior of electrons in reconnections events not only give scientists a better idea of how reconnection works, but also brings them closer to understanding space weather — such as solar flares and magnetic storms — and whether they follow any sort of predictable pattern like weather here on Earth.

So far, MMS has focused its attention on the sun-facing side of Earth’s magnetic field. In the future, the mission will be sent to the night side to investigate the teardrop-shaped tail of the magnetic field, where reconnection events are believed to be even more explosive.

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