Magnetosferen

Magnetosferen, or the magnetosphere, is the region surrounding a planet in which the planet’s magnetic field dominates the motion of charged particles. It is produced by the planetary dynamo in the core and shaped by interaction with the solar wind. The magnetosphere acts as a protective bubble, deflecting or trapping energetic particles and helping to shield the atmosphere from solar-wind erosion.

On the dayside, the solar wind compresses the magnetic field until the magnetopause is reached, at roughly about 10 Earth radii from the planet. Ahead of this boundary lies a bow shock where solar-wind plasma is slowed and heated. The nightside is stretched into a long magnetotail with lobes and a central plasma sheet, and the inner magnetosphere contains features such as the plasmasphere and radiation belts. The outer magnetosphere includes regions of open field lines and currents, like the ring current that contributes to geomagnetic activity.

Energy from the solar wind enters the magnetosphere mainly through magnetic reconnection at the dayside magnetopause and in the magnetotail. This transfer drives geomagnetic activity, substorms, and auroras, especially near the polar regions. The magnetosphere couples with the ionosphere, and magnetic-field variations produced here are monitored on the ground with indices such as Dst and Kp.

Variability in size and shape correlates with solar activity and wind conditions. Planets with strong internal dynamos, such as Jupiter and Saturn, possess extensive magnetospheres, while Mars lacks a global magnetic field. The magnetosphere concept also applies to other planetary bodies with magnetic fields and to their satellite environments.