Magnetosphere

A region around a celestial body where its magnetic field controls charged-particle motion in surrounding plasma. Its shape and boundaries result from interaction with external plasma and magnetic fields.

Solar wind: A stream of charged particles flowing outward from the Sun. Its pressure compresses the dayside and stretches the magnetosphere into a nightside tail.
Magnetic field: A physical field produced by electric currents and magnetic materials that exerts forces on moving charges and magnets. The body's magnetic field is the organizing influence that defines its magnetosphere.
Earth's magnetosphere: The magnetic environment surrounding Earth, shaped by the solar wind and Earth's internal magnetic field. It is the best-studied example, with directly measured boundaries and particle populations.
Aurora: A luminous display in a planet's upper atmosphere caused by energetic particles interacting with atmospheric gases. Magnetospheric particles guided toward the polar atmosphere produce Earth's auroras.
Induced magnetosphere: A magnetic environment produced when the solar wind interacts with a conducting ionosphere or other obstacle, rather than an intrinsic planetary field. Venus develops this type despite lacking a strong global intrinsic magnetic field.
Magnetopause: The boundary separating a magnetosphere from the surrounding plasma. It marks where the body's magnetic influence balances the solar wind.
Plasma: A state of matter consisting of free electrons and ions that collectively respond to electromagnetic fields. The magnetosphere is a region of plasma governed by magnetic forces.
Jupiter's magnetosphere: The extensive magnetic environment around Jupiter, powered by its strong field and plasma from Io. Its scale and internally supplied plasma differ sharply from Earth's solar-wind-dominated system.
Geomagnetic storm: A disturbance of Earth's magnetosphere driven by enhanced solar-wind energy and magnetic fields. Storms can disrupt satellites, navigation, radio communication, and electrical power systems.
Venusian ionosphere: The ionized upper atmosphere of Venus, which interacts directly with the solar wind. It helps deflect the solar wind without the intrinsic dipole that defines Earth's system.

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