MMS mission delivers promised measurements of ‘magnetic reconnection

Patricia Reiff, Ph.D., Professor of Physics and Astronomy at Rice

“Space weather is driven by the interactions between the solar wind and Earth’s magnetic field, and one of the most important of these interactions is ‘magnetic reconnection,’ a fundamental process that occurs when magnetic fields interact with plasmas,” said Rice University physicist Patricia Reiff, co-author of a new paper about MMS results that’s available online this week from the journal Science.

For Reiff and her MMS colleagues, including mission principal investigator and Rice alumnus James Burch, vice president of Southwest Research Institute in San Antonio, this week’s results are the culmination of a process that began with the initial idea for MMS more than 25 years ago.

Reiff said MMS, a collection of four identical spacecraft that orbit in a pyramid-shaped formation about 6 miles wide, is specifically designed to study region of space tens of thousands of miles above Earth’s surface that is a prime location for magnetic reconnection. This region, known as the “magnetopause,” is where the solar wind — a plasma of positive ions and negative electrons that stream continuously outward from the sun — comes in contact with Earth’s magnetosphere, the region of space dominated by Earth’s magnetic field.

“Magnetic reconnection is a fundamental process that’s responsible for the aurora borealis and australis and space storms here on Earth, as well as for solar flares on our own sun and analogous stellar flares elsewhere in the universe,” said Reiff, a professor of physics and astronomy at Rice who began studying Earth’s magnetosphere more than 45 years ago with instruments left on the moon by Apollo astronauts.

“When two magnets come together, reconnection is the process whereby the magnetic field rearranges itself to link the north pole of one magnet with the south pole of the other,” she said.

Reconnection occurs when the two magnets are not exactly co-aligned. If reconnection occurs in a vacuum or an electrically non-conducting medium like Earth’s lower atmosphere, the process occurs at the speed of light and has no effect on the surrounding medium.

But each medium of space measured by MMS — the solar wind and the magnetosphere — contain a fully ionized plasma that is an excellent electrical conductor. The plasma’s negatively charged electrons and positively charged ions orbit in opposite directions about a given magnetic field line.

MMS mission spacecraft assembly
The MMS mission’s four spacecraft stacked and ready for encapsulation in the launch nose cone at Kennedy Space Center. (Photo courtesy of NASA KSC)
“When the field lines of two different magnetic fields meet in space — as they do at the magnetopause — and try to reconnect, these gyrating particles initially resist,” Reiff said. “Each field line tends to retain its own distinct set of orbiting charged particles. Reconnection occurs when the field lines draw nearer one another than the distance of the ions or electrons orbiting them, and when it occurs, the energy released by the merger is transferred to the particles, which accelerate rapidly, sometimes at nearly light speed.”

This critical distance, known as the diffusion region, is considerably larger for ions than it is for electrons, and MMS is the first spacecraft designed to probe the much smaller “electron diffusion region” where the electrons become decoupled and reconnection actually occurs. The MMS plasma instruments are much faster than any previously deployed to measure the magnetosphere, and are thus designed to catch reconnection “in the act” on its most microscopic scale.

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Professor Patricia H. Reiff is a Professor in the Department of Physics and Astronomy and was the founding Director of the Rice Space Institute at Rice University. Her research focuses on space plasma physics, mostly in the area of magnetospheric physics: "space weather". Her research includes study of the aurora borealis, magnetic reconnection, solar wind-magnetosphere coupling (including solar wind control of magnetospheric and ionospheric convection), and magnetosphere-ionosphere coupling. She was the first person to prove, using Dynamics Explorer dual spacecraft data, that the aurora is caused by a mid-altitude electric field. She was a Co-I on the "IMAGE" magnetospheric imaging mission (launched March, 2000), Jim Burch, SWRI, P.I., and was the first to propose radio sounding of the magnetosphere, which that spacecraft included as a key instrument. She was a Co-Investigator on the "Peace" plasma instrument on the ESA "Cluster 2" 4-spacecraft suite which were launched in July and August 2000. She is a Co-Investigator for science and E/PO (Education and Public Outreach) on the "Magnetospheric Multiscale Mission" which launched in March 12, 2015. She is instrumental in bringing real-time space weather forecasts and "Space Weather" information to the public. Her "Space Weather" software, which can be found in many fine museums, can be downloaded free from She is a partner in the "Heliospheric Education Consortium" from NASA, and is developing "iClips", immersive educational clips for use in planetarium domes. She is working on a show on magnetism and will create a clip for the 2017 solar eclipse. She is the director for a major project which has developed an off-ramp for the information highway by "Creating the Public Connection" , bringing real-time earth and space science data to museums and schools (originally sponsored by NASA's Digital Library Technology Program). Over ten million people have interacted with her exhibits and planetarium shows at the Houston Museum of Natural Science and other museums, and another five million with her web sites. Over 300,000 of her educational CD and DVD-Roms and planetarium videos have been distributed through her spinoff company She has also been a leader in public education activities, including being director for four years for teacher education projects sponsored by the National Science Foundation and the Eisenhower Foundation, in collaboration with Dr. Carolyn Sumners of the Houston Museum of Natural Science (HMNS). Their latest collaboration is the creation and marketing of "Discovery Domes", portable digital theaters to teach earth and space science, with over 260 installations in 33 countries and 34 states, through her distribution company ePlanetarium. She has guided many scientific tours, including total solar eclipse trips to Canada in 1979, Louisiana (annular), Mexico in 1991, Peru in 1994, the Caribbean in 1998, the Black Sea in 1999, Madagascar in 2001, Libya in 2006, China in 2008 and 2009, Tahiti in 2010, annular in May 2012, Australia in November 2012, transatlantic in November 2013, and an Indonesian trip in 2016. = She is a Fellow of the American Geophysical Union , where she serves on the SPA Public Education Committee. In 2009, she received the AGU "Athelstan Spilhaus Award" and in 2013 she won the "SPARC" Award (Space Physics and Astronomy Richard Carrington Award) for service in public education. She is the Rice University representative and former Chair of the Council of Institutions of the USRA - the Universities Space Research Association. She has served on advisory committees for NASA, NSF, NCAR, Los Alamos National Laboratory, NAS/NRC and AAU. She tweets at "@discoverydome" and "@PatReiff"and has an outreach Facebook persona "Discovery Dome". She has a Youtube channel that has all her fulldome planetarium shows to view for free. Her educational videos about space science can be found at Her MMS Mascot "Trigger" has his own web page, his own "Trigger MMS" Facebook page, and twitter feed "@TriggerMMS"


Wednesday, August 16, 2017 - 16:00