The Magnetospheric Multiscale, or MMS, mission is scheduled to launch into space on March 12, 2015. The mission consists of four spacecraft to observe a phenomenon called magnetic reconnection - which doesn't happen naturally on Earth all that often, but is a regular occurrence in space. At the heart of magnetic reconnection is a fundamental physics process in which magnetic field lines come together and explosively realign, often sending the particles in the area flying off near the speed of light.

The process may sound a bit abstract, but it is at the heart of some very concrete events in space. Take, for example, a giant explosion on the sun that occurred on July 12, 2012, causing colorful aurora and space weather near Earth a few days later. Magnetic reconnection catalyzed numerous events along the way.

It all began at 12:11 p.m. EDT on July 12, 2012, when magnetic reconnection in the sun's atmosphere, the corona, led to a solar flare. Scientists don't yet know exactly what sets off one of these gigantic explosions of light and x-rays, but they know that magnetic reconnection - initiated in areas of complex and intense magnetic fields on the sun - is ultimately responsible.

Solar eruptions such as flares often occur in conjunction with a different kind of explosion that is also a consequence of reconnection called a coronal mass ejection, or CME. CMEs are giant clouds of solar material that erupt upward fast enough to achieve escape velocity and zoom out into space.

On July 12, that CME sped out from the sun with an initial velocity of 850 miles per second and headed straight toward Earth, as can be seen in this simulation of the CME created with a model, called an Enlil model, via the Community Coordinated Modeling Center at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

The material in a CME is made of very hot, charged particles, also known as plasma. This plasma carries embedded magnetic fields along for the ride. On July 14, 2012 at around 2 p.m. EDT, after traveling for two days, those magnetic field lines collided with the magnetic field that naturally surrounds Earth, a giant bubble called the magnetosphere where it soon experienced another bout of magnetic reconnection.

The magnetosphere's field lines naturally point from Earth's south magnetic pole to its north pole. Sometimes, the magnetic field lines inside a CME are pointed in the same direction and the collision is a reasonably gentle one: Solar material from the CME is rebuffed, and the magnetosphere itself doesn't feel much effect.

But this was not the case for this CME. The magnetic field lines in the plasma were pointed in the opposite direction of the field's lines around Earth - as can be seen in this graph from NASA's Advanced Composition Explorer, or ACE, which sits 1 million miles closer to the sun than Earth, just outside our magnetosphere.

This type of graph from ACE shows just how much of a north/south magnetic field component is present at any given time. Above the midline, the graph shows magnetic fields that point north like Earth's do; below the midline indicates magnetic fields that point south.

Note, in this case, the extended period of strong southward magnetic field on July 15 and 16. Over and over during this time period, whenever the CME's oppositely directed magnetic fields collided with Earth's magnetospheric lines, magnetic reconnection occurred right at the boundary of the magnetosphere.

During this period of repeated magnetic reconnection, surges of solar material breached the magnetosphere, zooming into near-Earth space. In this visualization of the magnetosphere, you can see how the magnetic fields lines at the front of the magnetosphere realign, peeling back like layers of an onion. As more lines are peeled back, more energy is dumped in the tail end of the magnetosphere, the magnetotail, giving rise to what's called a geomagnetic storm.

This visualization shows how excited the magnetosphere became after the CME passed by. Such space weather events can compress the front of the magnetosphere so satellites are left exposed to the more harsh radiation outside the magnetosphere.

The magnetic variation can also initiate electric currents flowing through grid lines on Earth, with the potential to damage transformers and disrupt utility power grids.

In the visualization, you can also see field lines connecting and realigning on the right side of Earth, in the magnetotail. As the magnetotail gets increasingly unstable, we see additional examples of magnetic reconnection.

The reconnection events sent particles shooting off down the tail, and also toward Earth, where they collided with particles in the atmosphere to create aurora. This image shows the red purple aurora that occurred in Missouri on July 15, 2012.

The orbit for MMS will carry it through the magnetic reconnection at the nose of the magnetosphere for over a year, and then switch to flying through areas of magnetic reconnection in the magnetotail.

MMS will offer us our first ever three-dimensional view of this process as it is happening, which will provide unprecedented amounts of information to help scientists better understand what sets it off and what effects it causes near Earth.

Groups like NASA's Community Coordinated Modeling Center can then take that information to improve models such as those seen here, which can be used by NOAA's Space Weather Prediction Center - the U.S. government's official source for space weather forecasts, alerts, watches and warnings - uses to forecast space weather.

MMS is the fourth NASA Solar Terrestrial Probes Program mission. NASA Goddard built, integrated, and tested the four MMS spacecraft and is responsible for overall mission management and mission operations. The Southwest Research Institute in San Antonio, Texas, leads the Instrument Suite Science Team. Science operations planning and instrument command sequence development will be performed at the MMS Science Operations Center at the University of Colorado's Laboratory for Atmospheric and Space Physics in Boulder. ?