There's something strange in the tail of Earth's magnetic field. Where scientists expect to find violent space storms, an unexpected calm suddenly seems to reign. This is the mystery that the mission Magnetospheric Multiscale (MMS) NASA is now trying to solve.
Four satellites, launched in 2015, I've been working for a while to figure out what's going on in this remote region of space, where the rules of physics seem to have been overturned.
The tail of the magnetic field and its storms
You may not know it, but Earth's magnetic field has a tail. When the solar wind of our star hits us, leaves behind it a sort of long shadow that trails in the wake of our planet. Scientists call this magnetic tail, appropriately, the magnetotail. And typically, the magnetotail is littered with magnetic storms.
These storms, called substorms, are triggered by a phenomenon known as magnetic reconnection. In other words, the lines that make up a magnetic field they come together, break apart, and then rejoin, creating brilliant bursts of heat and kinetic energy. (If these reconnections happen in Earth's atmosphere, they can cause auroras.)
The anomaly detected by the MMS mission
For several years, as mentioned, scientists have been aware of a mystery in the magnetotail: a storm missing. They have found the signature of a storm, but no actual storm to accompany it. In 2017, MMS detected the characteristic magnetic reconnection of a substorm, but no actual substorm accompanying it. A substorm would be accompanied by violent electrical currents and magnetic field fluctuations, but MMS detected no trace of either.
“We have not looked at the movement of magnetic field lines on a global scale, so it could be that this unusual substorm was a very localized event that MMS was lucky to observe,” he said Andy Marshall of the Southwest Research Institute. “If not, it could reshape our understanding of the relationship between tail-side reconnection and substorms.”
Observations from space and simulations on the ground to solve the puzzle
For the next year, MMS will measure magnetic reconnections in Earth's real magnetic field, while scientists on the ground will conduct simulations of the magnetic field to understand how it behaves. By comparing the two, scientists hope to solve the mystery by understanding better the precise relationship between the reconnection and the events what cause.
“It is possible that significant differences exist between global magnetotail convection models for substorms and queue reconnection does not substorm,” Marshall said.
Implications for understanding the Earth's magnetic field
Solving this puzzle could have significant implications for our understanding of Earth's magnetic field and how it interacts with the solar wind. The magnetic field is a crucial component of the “shield” that protects the Earth from charged particles from the Sun, which can cause damage to satellites, power grids and even the health of astronauts in space.
Better understanding the mechanisms of magnetic storms and reconnections could help us predict and potentially mitigate the effects of the most violent solar storms, which pose a real threat to our increasingly technological society.
Another frontier of space exploration
The MMS mission also represents another example of how space exploration is pushing the boundaries of our knowledge. While we aren't physically exploring the magnetotail with astronauts, our robotic eyes and ears, in the form of satellites like MMS's, are allowing us to shed new light on regions of space that remain largely mysterious.
In this sense, solving the mystery of the missing magnetic storm is not just a matter of scientific curiosity. It's part of an ongoing effort to understand our place in the universe, and how cosmic forces shape our world.
As MMS continues its mission, and scientists on the ground work to decipher its data, we can only marvel at the complexity and beauty of the system that supports us. And we can be grateful for explorers, both human and robotic, who are working tirelessly to unlock the secrets of the cosmos.
Who knows what other surprises await us in the long magnetic shadow of the Earth? With missions like MMS at the forefront, we're sure to learn much more in the years to come. And every new discovery, every mystery solved, brings us one step closer to a more complete understanding of our extraordinary planet and its place in the vast tapestry of space.
