The United Launch Alliance Atlas V rocket with NASA’s Magnetospheric Multiscale (MMS) spacecraft on board launches from the Cape Canaveral Air Force Station Space Launch Complex 41, Florida, on Thursday, March 12, 2015.NASAMagnetic reconnection takes place high above the planet in the magnetosphere, a protective barrier around Earth that deflects the powerful solar winds that emanate from our sun. During that deflection, the plasma energy in the solar wind—which also contains magnetic fields—interacts violently with the magnetosphere, transferring energy in explosive realignments that send particles in the area flying off at speeds near that of light.

MMS will investigate how the magnetic fields of the sun and Earth connect and disconnect by using four identical spacecraft, each with 11 instruments, to study plasmas, fields, and particles. The mission will provide data about magnetic fields, plasma, and particle acceleration that will answer long-standing questions scientists have had about these reconnection events.

"The process of magnetic reconnection that MMS will study is the means by which the energy from the sun gets inside the magnetosphere, through tears along magnetic field lines," said Barry Mauk of APL, the lead investigator of the mission's Energetic Particle Detector (EPD) investigation team. "Also, magnetic reconnection is the process that allows the energy of the solar wind into the magnetosphere. That energy creates powerful phenomena like the Van Allen radiation belts." These doughnut-shaped hazardous regions of highly-charged particles above Earth are studied by another NASA mission, the Van Allen Probes, for which Mauk is project scientist, and which were built and are operated by APL.

MMS will explore different regions where magnetic reconnection often occurs, one on the day-side and the other on the night-side of Earth.NASA"These regions where the magnetic reconnection occurs can be quite small, relatively speaking," Mauk said, "sometime only tens of miles, or a few dozen kilometers, in size." By using four spacecraft, researchers will be able to see the reconnection regions in three dimensions, and hope to better and more clearly understand the many physical processes at work.

There are 11 instruments on board each spacecraft; the EPD team will use two instruments to focus on the detection of energetic particles, some of which are accelerated to near-relativistic speeds. (The team is made up of researchers from four institutions: APL; the University of Colorado's Laboratory for Atmospheric and Space Physics (LASP) in Boulder; Los Alamos National Laboratory, New Mexico; and the University of New Hampshire. The EPD payload lead is the Southwest Research Institute in San Antonio, Texas.)

In addition to the APL-built EIS, which will make comprehensive measurements of ions in the region, a second instrument, the Fly's Eye Energetic Particle Sensor (FEEPS, built by the Aerospace Corporation), will record the number and direction of electrons in the area. Together, the instruments allow MMS to take fast, accurate ion and electron measurements as the spacecraft operate through fast-changing reconnection sites. (APL also contributed other electronics and testing to the mission.)

"MMS will help us better understand the processes occurring in these magnetic reconnection events," Mauk said. "It's the first time we'll be able to have a multi-spacecraft mission specifically study what is going on in these reconnection regions, and we hope to prove which theories about particle acceleration and other fundamental universal processes are correct."