NASA spacecraft have managed to observe a magnetic thunderstorm caused by Earth’s magnetic field crossing the Sun’s for the first time.While space may be a vacuum, it contains a lot of energy and a system of magnetic fields surrounding massive bodies.
Earth's magnetic field, for example, provides an invisible barrier that protects life on the planet from the Sun's magnetic fields.
Sometimes, however, the boundaries can cross, causing an explosive reaction that creates effects like eruptions of the Sun, aurora and radiation storms.
The effects of these reconnection events had been measured before, but the event itself had never been directly observed.
NASA’s Magnetospheric Multiscale mission was developed for just that purpose.
A video outlining the MMS mission to observe magnetic field reconnections. Credit: NASA's Goddard Space Flight Center/Duberstein
NASA flew four spacecraft through the reconnection and managed to observe it directly for the first time.
The observations will help scientists learn more about near-Earth space and the effect of radiation.
“We received results faster than we could have expected,” says Jim Burch, principal investigator for MMS at the Southwest Research Institute.
“By seeing magnetic reconnection in action, we have observed one of the fundamental forces of nature."
MMS consists of four identical spacecraft that collect data to create a 3D map of the phenomena they observe.
On 16 October 2015, they flew through a magnetic reconnection event where Earth’s magnetic field meets the Sun’s.
The 25 sensors on each of the spacecraft collected thousands of observations of the event.
Magnetic fields are connected to a cosmic body, such as a planet or star, and create a giant magnetic network.
Sometimes these fields are travelling in the same direction to their neighbour, and do not cause much of a reaction at the point where they meet.
But if the two sets are travelling in opposite directions, the effect is explosive.
"One of the mysteries of magnetic reconnection is why it’s explosive in some cases, steady in others, and in some cases, magnetic reconnection doesn’t occur at all," says Tom Moore, mission scientist for MMS.
When the reaction occurs, the local particles are fired away from their source and cross other magnetic boundaries.
When this happens near Earth, for example, it can cause solar radiation to enter near-Earth space.
Once the electrons cross the magnetic boundaries, they curve back on themselves, making a U-turn.
This effect had been predicted previously in computer simulations, but the direct observations have confirmed this is the case.
What’s more, the rebounding electrons began to flow along the magnetic field lines of their neighbour, creating the breaking and reconnection event.
"This shows us that the electrons move in such a way that electric fields are established and these electric fields in turn produce a flash conversion of magnetic energy,” says Roy Torbert, co-author on the paper.
“The encounter that our instruments were able to measure gave us a clearer view of an explosive reconnection energy release and the role played by electron physics."
