What is meant by the term "magnetic variation" in aviation?

The term "magnetic variation" in aviation refers to the difference between true north and magnetic north. This is crucial for navigators, as aircraft compass systems rely on magnetic north for directional guidance. However, true north is based on the geographic North Pole.

The existence of magnetic variation is due to the Earth's magnetic field not aligning perfectly with its rotational axis. Thus, pilots must account for this variation when plotting their courses to ensure accurate navigation. By understanding and applying magnetic variation, aviators can adjust their headings accordingly, allowing for more precise navigation across different geographical areas, as magnetic variation varies depending on where you are on the planet.

Considering the other choices, they describe unrelated concepts such as weather influences on magnetic forces or altitude effects, which do not pertain to the fundamental definition of magnetic variation in the context of navigation.