The area of space influenced by Earth’s magnetic field is called the magnetosphere. Within this protective bubble, scientists have observed an electric force that moves from the morning side of the planet toward the evening side. This vast electric field plays a crucial role in generating disturbances in near-Earth space, including geomagnetic storms.

Because electric forces move from positive to negative charges, researchers once believed that the morning side of the magnetosphere carried a positive charge while the evening side was negative. However, new satellite data has revealed the reverse: the morning side is actually negatively charged, and the evening side is positively charged.

This unexpected finding led a research group from Kyoto University, Nagoya University, and Kyushu University to take a closer look at the mechanisms that shape the magnetosphere.