NASA to Launch Satellites into Powerful Magnetic Explosions

Magnetic reconnection is ubiquitous — wherever there’s a magnetic field there’s the potential for the field to ‘snap’, reconnect and, if the magnetic field is embedded in an energetic plasma, explode.

Although the physical phenomenon has been observed to occur in everything from the sun’s corona to the tokamaks inside experimental fusion reactors, scientists are not entirely clear what triggers it and why the result of reconnection is often highly energetic.

Tomorrow, NASA hopes to change that by launching a formation-flying group of probes into the Earth’s very own reconnection ‘laboratory’, the magnetosphere.

Countless pages of physics textbooks are devoted to the theory behind magnetic reconnection, but the science remains difficult to understand. The simple act of magnetic field lines crossing is often all it takes for reconnection to occur, but why does it often result in such an energetic reaction? Two very visible solar phenomena, solar flares and coronal mass ejections, are driven by magnetic reconnection — field lines break, reconnect and rapidly accelerate plasma through the corona, often generating powerful blasts of X-ray radiation.

At the opposite end of the scale, inside experimental fusion chambers on Earth, powerful magnetic fields are used to contain and control the plasma undergoing fusion. However, instabilities in the magnetic field cause small-scale reconnection events that can interrupt experiments.

“For many years, researchers have looked to fusion as a clean and abundant source of energy for our planet,” said Jim Burch of the Southwest Research Institute. “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 said in a NASA news release. “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.”

Unfortunately, these events cannot be properly studied as they occur over tiny volumes that are too small to be probed.

So rather than trying to catch reconnection in the act in the laboratory, Burch and his team have built a constellation of satellites that will be launched into the Earth’s very own reconnection factory on Thursday (March 12).

“Earth’s magnetosphere is a wonderful natural laboratory for studying this phenomenon,” he said.

Guided by GPS and flying in formation around 10 kilometers apart, the four Magnetospheric Multiscale (MMS) satellites will embed themselves in the magnetic environment surrounding our planet.

The Earth’s magnetosphere acts to deflect charged particles from the sun, but it is also shaped by the solar wind and the sun’s own magnetic field. Geomagnetic storms, for example, are ripples generated through the magnetosphere, often triggering reconnection events in the magnetosphere’s tail, that go on to accelerate solar plasma, injecting it into the Earth’s magnetic poles. Magnetospheric reconnection events therefore drive auroral activity at high latitudes.

But unlike the tiny scales impossible to measure in fusion reactors, reconnection zones in the magnetosphere are far bigger and MMS will be embedded inside the region to take high-resolution look at magnetic reconnection in action.

“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 NASA’s Goddard Space Flight Center in Greenbelt, Md. “When fully extended, the sensors are as wide as a baseball field.”

Read more at Discovery News