Scientists have found that something unusual is happening at the tail of the Earth's magnetic field.
When the solar wind hits the planet, it leaves behind a kind of long shadow that extends away from the planet from the Earth's magnetosphere in the opposite direction of the Sun, in the form of a tail called the magnetotail.
This means that the magnetotail is littered with energetic particles, which can sometimes be discharged by a turbulent event called a magnetospheric substorm.
But, over the past several years, scientists have learned about the magnetotail's secret: a missing storm, where they detected the signature of the storm but never found an actual storm to match it.
A team from the Southwest Research Institute (SwRI) examined data collected by NASA's Magnetosphere Multimission Mission (MMS) to solve this long-standing mystery surrounding substorms.
In 2015, NASA launched the Magnetosphere Multimission Mission (MMS) to closely study this magnetic region and decipher how magnetic reconnection occurs (a process in which opposing magnetic field lines merge).
The Magnetosphere Multimission Mission is exploring this region to look for signs of magnetic reconnection, leading to substorms.
In 2017, the Magnetosphere Multimission Mission observed magnetic reconnection without an actual substorm to accompany it. The substorm is supposed to be accompanied by violent electrical currents and fluctuations in the magnetic field, but the multi-tasking magnetospheric mission did not detect traces of either.
Strong electrical currents and magnetic field changes in the magnetotail are key indicators of a substorm, but MME data showed no such signs.
In the new one-year study, the Southwest Research Institute (SwRI) will compare MMS data with reconstructions of the global magnetosphere to uncover the secrets of this mysterious phenomenon.
“We want to see how the local physics observed by the Magnetosphere Multimission Mission affects the entire magnetosphere,” said Andy Marshall, a postdoctoral researcher at the Southwest Research Institute.
“By comparing this event to more typical substorms, we strive to improve our understanding of substorm causes and the relationship between substorms and reconnection,” Marshall added.
The Community Coordinated Modeling Center at NASA's Goddard Space Flight Center will use the University of Michigan's space weather modeling framework to develop reconstructions of the global magnetosphere.
“It is possible that there are significant differences between the global convection patterns of substorms and tail reconnection without substorms,” Marshall explained. “We did not look at the movement of magnetic field lines on a global scale, so it is possible that the absence of this unusual substorm was a very local event that occurred.” "If it is not observed by the Magnetosphere Multimission Mission, it may reshape our understanding of the relationship between tail-side reconnection and substorms."
The multi-mission magnetospheric mission consists of four identical spacecraft and is part of the mission of NASA's Solar Terrestrial Probes program. It was built by NASA's Goddard Space Flight Center.
Since its launch, the space mission has explored the magnetic divide, which is the boundary between the Earth's magnetic field and the solar wind.