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Magnetospheric Multiscale

Phase: Operating

Launch Date: March 2015

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Program(s):Heliophysics Research, Solar Terrestrial Probes

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MMS will investigate how the Sun's and Earth's magnetic fields connect and disconnect, explosively transferring energy from one to the other in a process that is important at the Sun, other planets, and everywhere in the universe, known as magnetic reconnection. Reconnection limits the performance of fusion reactors and is the final governor of space weather that affects modern technological systems such as telecommunications networks, GPS navigation, and electrical power grids. Four identically instrumented spacecraft will measure plasmas, fields, and particles in a near-equatorial orbit that will frequently encounter reconnection in action.

MMS will reveal, for the first time, the small-scale three-dimensional structure and dynamics of the elusively thin and fast-moving electron diffusion region. It will do this in both of the key reconnection regions near Earth, where the most energetic events originate.

The four identically instrumented MMS spacecraft will fly in an adjustable pyramid-like formation that will allow them to observe the three-dimensional structure of magnetic reconnection. MMS sensors will measure charged particle velocities, as well as electric and magnetic fields, with unprecedented (milliseconds) time resolution and accuracy needed to capture the elusively thin and fast-moving electron diffusion region. MMS probes reconnection of solar and terrestrial magnetic fields in the dayside and nightside of Earth's magnetosphere, the only natural laboratory where it can be directly observed by spacecraft.