Corioliskraft

Corioliskraft is the apparent sideways force observed in a rotating reference frame, acting on moving objects. It is not a real interaction in inertial space but arises from the rotation of the frame itself. The concept is central in meteorology, oceanography and ballistics, where it explains systematic deflections of trajectories on Earth.

In a frame that rotates with angular velocity vector Ω, the Coriolis acceleration is a_c = -2 Ω × v, where v is the velocity relative to the rotating frame. The corresponding force on a mass m is F_c = -2 m Ω × v. The Coriolis parameter f = 2 Ω sin φ is often used in geophysical equations, with φ the latitude.

The direction of deflection is perpendicular to both the motion and the axis of rotation. In the Northern Hemisphere moving objects tend to turn to the right; in the Southern Hemisphere to the left. The magnitude scales with speed and latitude, being zero at the equator (sin φ = 0) and maximal near the poles.

Practical effects include the formation and sustenance of large-scale wind patterns under geostrophic balance and the rotation of oceanic gyres. It also requires corrections in long-range artillery and ballistics. A Foucault pendulum and various demonstrations show the influence of Earth’s rotation that is captured in Corioliskraft analyses.

The force is named after Gaspard-Gustave de Coriolis, who described the mathematical effect in 1835. The Earth's rotation determines the Coriolis parameter f ≈ 2Ω sin φ, with Ω ≈ 7.2921159×10^-5 s^-1.