Kyoto, Japan -- The region of space dominated by Earth's magnetic field is the magnetosphere. Observations have shown that, within this region, an electric force acts from the morning side to the evening side as seen from Earth. This large-scale electric field is known to be a key driver of various disturbances such as geomagnetic storms.

Since electric forces act from positive charge to negative, it has been thought by some that the magnetosphere is positively charged on the morning side and negatively charged on the evening side. Yet recent satellite observations have revealed that this polarity is actually the opposite.

This discovery prompted a team of researchers from the universities of Kyoto, Nagoya, and Kyushu to reexamine the underlying mechanisms of the magnetosphere.

A Dartmouth-led study identifies potentially more that 300 small galaxies orbiting low-mass systems known as dwarf galaxies. If confirmed, these satellite galaxies—which are about one-tenth the size of the Milky Way—could provide new, clearer insight into galaxy formation and its connection to dark matter. The study triples the number of dwarf galaxies that have been surveyed in search of satellite star systems.