On March 12, 2015, NASA plans to launch the Magnetospheric Multiscale, or MMS, mission. MMS consists of four identical spacecraft that will orbit around Earth through the dynamic magnetic system surrounding our planet to study a little-understood phenomenon called magnetic reconnection. The MMS mission is a Solar Terrestrial Probes mission comprising four identically instrumented spacecraft that will use Earth’s magnetosphere as a laboratory to study the microphysics of three fundamental plasma processes: magnetic reconnection, energetic particle acceleration, and turbulence. These processes occur in all astrophysical plasma systems but can be studied in situ only in our solar system and most efficiently only in Earth’s magnetosphere, where they control the dynamics of the geospace environment and play an important role in the processes known as “space weather.”

Orbiting Earth, MMS will pass through known areas of magnetic reconnection. During its first phase it will travel through reconnection sites on the sun side of Earth. Here the interplanetary magnetic field connects with Earth’s magnetic field, transferring particles, momentum and energy to the magnetosphere via magnetic reconnection. During the second phase of its mission, MMS will observe reconnection on the night side of Earth, where that connected field flows around both sides of Earth to a second reconnection point in what’s known as the magnetotail, where they then disconnect.

Under normal conditions, the magnetic field lines inside plasmas don’t break or merge with other field lines. But sometimes, as field lines get close to each other, the entire pattern changes and everything realign into a new configuration. The amount of energy released can be formidable. Magnetic reconnection taps into the stored energy of the magnetic field, converting it into heat and kinetic energy that sends particles streaming out along the field lines.

Scientists want to know exactly what conditions, what tipping points, trigger magnetic reconnection events. Much of what we currently know about the small-scale physics of magnetic reconnection comes from theoretical studies, computer models, and laboratory experiments. True understanding, however, requires observing magnetic reconnection up close – so MMS will take its measurements in Earth’s own magnetosphere, an ideal natural laboratory in which reconnection can be observed under a wide range of conditions.

Armed with this data, scientists will have their first chance to watch magnetic reconnection from the inside, right as it’s occurring. By focusing on the small-scale process, scientists open the door to understanding what happens on larger scales throughout the universe.  Determining how reconnection occurs nearby will improve our understanding of how this fundamental process works on the sun, on other stars, throughout space — and, of course, it will teach us more about giant geomagnetic storms like the Halloween storms, thus helping us safeguard our home planet Earth.

For more on MMS: www.nasa.gov/mms