Scientists detect a magnetic reversal near Earth for the first time

A NASA fleet has spotted the first magnetic switchback near Earth, a zigzag in the magnetic field at the edge of our planet’s shield. The result shows that twists once seen near the Sun also appear in our space neighborhood.

The work was led by E. O. McDougall, a physicist, at the University of New Hampshire (UNH).
McDougall’s research focuses on magnetic switchbacks and reconnection in space plasmas.

Near Earth, the magnetosphere, the protective magnetic bubble that steers charged particles around the planet, stands between us and the Sun’s flow.

NASA’s Magnetospheric Multiscale Mission (MMS) was skimming that boundary when the field captured scale changes in particles and fields.

What makes a magnetic switchback

Parker Solar Probe revealed that switchbacks are common near the Sun, but their origin has been debated.
NASA explains that switchbacks are traveling disturbances in the solar wind, the fast stream of charged particles from the Sun.

A switchback is tied to magnetic reconnection, the breaking and rejoining of magnetic field lines that releases energy. That physics helps heat the solar atmosphere and powers near Earth disturbances.

Catching a twist in motion

The team describes a twisting patch of plasma that rotated and then rebounded to its original direction. Inside it, high energy electrons moved along the field, a clue that material came from within Earth’s field.

The structure sat in the magnetosheath, the turbulent layer just outside the magnetosphere where diverted solar wind flows around our magnetic bubble.

There, MMS measured a current sheet, a thin layer where electrical current is concentrated, that was actively reconnecting.

One part of the event featured a guide field, a magnetic component that runs along the reconnection layer, with a reported strength of 1.2.

The team also used a z parameter, a measure of how far the field direction rotates, which exceeded 0.5 to classify the structure as a switchback.

“This magnetic switchback was formed via interchange reconnection at the interface between open magnetosheath and closed magnetospheric field lines,” wrote McDougall. 

Implications for space weather

These twists matter because they mix solar and terrestrial plasma, which can change how energy moves into the upper atmosphere. When that energy surges, power grids, radio links, and satellites can feel the strain.

MMS was built to study reconnection with fast instruments that can catch split second changes.
The mission flies four identical spacecraft in formation so scientists can see how reconnection evolves in three dimensions.

Finding a switchback here means researchers can now probe this physics near Earth without sending a probe into the Sun’s furnace. That creates a practical test bed for forecasting space weather, the conditions in near Earth space that affect technology and astronauts.

A nearby lab for Sun physics

Recent research links many interplanetary switchbacks to reconnection at the Sun’s network boundaries.

Other work has provided direct evidence that reconnection happens at switchback edges in the inner heliosphere.

If a similar process happens where the solar wind meets Earth’s field, that helps unify a lot of puzzling observations.

It also suggests that the magnetosphere can twist open field lines upon themselves and then relax, leaving a switchback shaped imprint that can be mapped in detail.

With MMS, scientists can time how long the field rotates, measure particle speeds, and compare with models of reconnection and turbulence.

Those checks can reveal how often events inject energy into the system and whether they seed larger disturbances.

Tracking magnetic switchbacks

Future passes will let the team test how often switchbacks form at this boundary and what conditions trigger them.

They can compare events during quiet periods and during fast streams to untangle the roles of turbulence and reconnection.

Modelers can fold these observations into physics based simulations and watch how energy cascades across scales.

That helps set better bounds on when a small twist is harmless and when it primes a larger disturbance.

Space agencies can then refine alerts for operators who manage satellites, crewed missions, and long distance radio links.

A clearer picture of injection pathways can also guide new instruments that target the thin layers where reconnection works fastest.

Pinpointing where it happened

The event likely unfolded near the magnetopause, the moving boundary where solar wind pressure balances Earth’s field. That frontier shifts with conditions, which helps explain why some orbits will miss short lived twists.

Because each MMS craft samples a point, timing across the four spacecraft recovers the shape, speed, and thickness of a structure.

Those numbers will tell researchers whether switchbacks behave more like waves passing through or objects carried by the flow.

The study is published in the Journal of Geophysical Research.

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