Ekzosfera

Ekzosfera, or exosphere, is the outermost layer of Earth's atmosphere and the gradual boundary where the atmosphere transitions into interplanetary space. In this region the air is extremely tenuous, and collisions between particles are rare. Gas molecules can travel long distances, following ballistic paths, and some eventually escape into space.

The altitude range of the ekzosfera is not fixed. Most definitions place the lower boundary around 600 to 800 kilometers above the Earth's surface, with the exosphere extending upward to roughly 10,000 kilometers or more. Beyond this, the distinction between atmosphere and space becomes increasingly blurred as particle density diminishes toward the solar wind and solar radiation dominates the environment.

Composition in the ekzosfera is dominated by the lightest elements, primarily hydrogen and helium, with trace amounts of heavier species such as atomic oxygen and nitrogen. The region contains both neutral atoms and ions, the latter produced by solar ultraviolet radiation and interactions with the solar wind. The exosphere exhibits high temperatures driven by solar heating, but the sparse particle population means that thermal energy translates into high-velocity, long-range trajectories rather than dense gas behavior.

A key process in the ekzosfera is atmospheric escape, where light components like hydrogen reach escape velocity due to the Jeans escape mechanism. The exosphere overlaps with the thermosphere below and the interplanetary space above, and its dynamics are influenced by solar activity and Earth's magnetic environment. Studied for insights into atmospheric evolution and for understanding the near-space environment impacting satellites and space missions, the ekzosfera remains a transitional, poorly defined region rather than a sharp boundary.