Although you might not think it, Earth's magnetic field is just as essential to life on the planet as air, water and sunlight, providing us with the critical barrier that protects us from the sun's magnetic field. Now, a new study using results from NASA's Magnetospheric Multiscale (MMS) mission provides the first look at the interaction between the magnetic fields of Earth and the sun and gives the first direct observation of magnetic reconnection, a phenomenon that occurs when two opposing magnetic field lines break and then reconnect.
"Imagine two trains traveling toward each other on separate tracks, but the trains are switched to the same track at the last minute," said James Drake, a professor of physics at the University of Maryland and co-author of the study. "Each track represents a magnetic field line from one of the two interacting magnetic fields, while the track switch represents a reconnection event. The resulting crash sends energy out from the reconnection point like a slingshot."
Previous research has suggested that reconnection is the major force behind interstellar events such as solar flares and magnetic storms, although direct observation of this phenomenon has never happened, until now.
The MSS spacecraft flew in a pyramid formation at the edge of Earth's magnetic field and captured electrons within the pyramid once every 30 milliseconds, much more than the previous Cluster II mission, which took measurements every three seconds.
"Just looking at the data from MMS is extraordinary," Drake said. "The level of detail allows us to see things that were previously a blur. With a time interval of three seconds, seeing reconnection with Cluster II was impossible. But the quality of the MMS data is absolutely inspiring. It's not clear that there will ever be another mission quite like this one."
Shedding light on magnetic reconnection will allow us to better understand space weather and determine any potential patterns similar to those seen in the weather on Earth. In addition, it can help us understand other mysterious astrophysical phenomena such as magnetars - neutron stars with a strangely strong magnetic field.
"Understanding reconnection is relevant to a whole range of scientific questions in solar physics and astrophysics," said Marc Swisdak of the University of Maryland, who was not involved in the current study.
"Reconnection in Earth's magnetic field is relatively low energy, but we can get a good sense of what is happening if we extrapolate to more energetic systems," he added. "The edge of Earth's magnetic field is an excellent test lab, as it's just about the only place where we can fly a spacecraft directly through a region where reconnection occurs."
The findings were published in the May 12 issue of the journal Science.
