Here’s what you’ll learn when you read this story:

• The Earth’s magnetosphere protects life from deadly space radiation, but many aspects of its function remain a mystery.
• Scientists have long believed that the magnetosphere’s charge-polarity was uniform from the poles to the equator, but new satellite data suggests that the equator actually maintains a reverse polarity.
• Understanding this environment is crucial, as this magnetic differential generates an electric field that plays a significant role during geomagnetic storms.

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Due to the movement of iron and nickel in our planet’s outer core, Earth is essentially a giant dynamo, continuously creating a magnetic field that forms the core of the magnetosphere—a protective bubble that protects life from the various radiative dangers of space. One of the quirks of the magnetosphere is that it contains what’s called a charge polarity, where the “morning side” is positively charged and the “evening side” is the opposite. This creates an electric field that can have a profound effect on geomagnetic disturbances, such as solar storms.

However, the traditional view of this global positive-negative charge polarity turns out to be more complicated than we originally thought. According to new satellite observation data, the reverse of this view is actually true—at least around the equator. In a new study published in the journal JGR Space Physics, a team of Japanese scientists (from Kyoto University, Nagoya University, and Kyushu University) discovered that near the equator, the morning side of the magnetosphere is negative and the evening side is positive. Near the poles, however, the magnetosphere adheres to scientists’ original charge-polarity view.

To look at this discrepancy more closely, the scientists used large-scale magnetohydrodynamic (MHD) simulations to recreate near-Earth space. Then, they simulated a stream of solar wind and found that the simulation matched up with this new satellite data. But what exactly is causing this latitudinal change in charge-polarity?

“In conventional theory, the charge polarity in the equatorial plane and above the polar regions should be the same. Why, then, do we see opposite polarities between these regions?” Yusuke Ebihara from Kyoto University said in a press statement. “This can actually be explained by the motion of plasma.”

To understand the role of plasma in this mystery, you’ll need to know about Earth’s magnetic field lines. These invisible lines travel in continuous loops and are nearly vertical at the planet’s magnetic poles. When the Sun’s magnetic energy (or plasma) enters the magnetosphere, it moves clockwise on the dusk side of the planet, channeling toward the poles. However, the field lines run in opposite orientations, and it’s these opposing forces that create the different polarities in different regions of the magnetosphere. “The electric force and charge distribution are both results, not causes, of plasma motion,” Ebihara said in a press statement.

Not only does this discovery provide valuable insight into near-Earth space conditions, particularly during solar storms (which are becoming more frequent), it gives us clues about the magnetic conditions surrounding other planets, such as Jupiter and Saturn.

This study also shows that there’s still much more to learn about the dynamic magnetic conditions that surround Earth. Just last year, NASA announced the discovery of an entirely new global ambipolar electric field, which the agency claims is as fundamental as the Earth’s magnetic and gravitational fields.

Darren lives in Portland, has a cat, and writes/edits about sci-fi and how our world works. You can find his previous stuff at Gizmodo and Paste if you look hard enough.