Yläilmakean

Yläilmakean is the genitive form of yläilmakehä, the Finnish term for the upper layers of Earth's atmosphere. The base ilmakehä means atmosphere, and ylä- indicates “upper.” The suffix -n marks the genitive, so yläilmakean means “of the upper atmosphere.” In scientific Finnish, yläilmakehä is the standard term for the region, while yläilmakean is used in possessive phrases such as “yläilmakean koostumus” (composition of the upper atmosphere).

Broadly, the upper atmosphere includes the mesosfääri (mesosphere) and thermosfääri (thermosphere), roughly from about 50–60 kilometers above the surface up to several hundred kilometers. The Kármánlinja, near 100 kilometers, is often treated as the boundary to space in practical discussions.

Research on the yläilmakean focuses on atmospheric chemistry, temperature profiles, and solar-terrestrial interactions. Measurements rely on satellites, sounding rockets, lidars, and radar. Phenomena such as auroras and satellite drag are associated with this region and influence space-weather studies and satellite operations.

In Finnish usage, the term appears primarily in scientific and educational contexts; in everyday language, yläilmakehä is the more common form. The exact usage can vary by field and author, and there is no single universal boundary for the yläilmakean across disciplines.