Astronomy & Astrophysics 101: Magnetosphere

What Is a Magnetosphere?

Earth is surrounded by a giant magnetic bubble called the magnetosphere, which is is part of a dynamic, interconnected system that responds to solar, planetary, and interstellar conditions. Credit: NASA

A magnetosphere is the region surrounding a planet that is dominated by its magnetic field. While other planets in our solar system also have magnetospheres, Earth’s stands out as the strongest among the rocky planets. This vast, comet-shaped magnetic bubble has been essential to Earth’s habitability, providing protection that has allowed life to develop and thrive. The magnetosphere shields the planet from harmful solar and cosmic radiation and prevents the solar wind — a continuous stream of charged particles from the sun — from eroding our atmosphere.

Earth’s magnetosphere is part of a dynamic and interconnected system influenced by solar, planetary, and interstellar forces. It is powered by the movement of electrically charged, molten iron deep within Earth’s outer core. The constant bombardment of solar wind compresses the magnetosphere on the sun-facing side, known as the dayside, which extends six to ten times Earth’s radius. On the opposite side, the nightside magnetosphere stretches outward into a vast magnetotail that fluctuates in length, reaching hundreds of Earth radii and extending well beyond the moon’s orbit.

NASA heliophysics studies the magnetosphere to better understand its role in our space environment. Such research helps unravel the fundamental physics of space, which is dominated by complex electromagnetic interactions unlike what we experience day-to-day on Earth. By studying this space environment close to home, we can better understand the nature of space throughout the universe. Additionally, space weather within the magnetosphere — where many of our spacecraft reside — can sometimes have adverse effects on space technology as well as communications systems. Better understanding of the science of the magnetosphere helps improve our space weather models.

NASA’s studies of the magnetosphere include research into: understanding the nature of the electromagnetic phenomena in near-Earth space; how near-Earth space responds to external and internal stimuli; how the coupled middle and upper atmosphere respond to external factors; and how the various regions of the magnetosphere and upper atmosphere interact with each other.