ioncyklotronfrekvensen

The ion cyclotron frequency, often denoted as $\omega_{ci}$ or $f_{ci}$, refers to the angular frequency or frequency, respectively, at which a charged ion will gyrate or orbit in a uniform magnetic field. This motion is a consequence of the Lorentz force acting on the charged particle. When an ion with charge $q$ and mass $m$ moves in a magnetic field $\mathbf{B}$, it experiences a force given by $\mathbf{F} = q(\mathbf{v} \times \mathbf{B})$, where $\mathbf{v}$ is the velocity of the ion. If the velocity has a component perpendicular to the magnetic field, this force acts as a centripetal force, causing the ion to move in a circular path. The radius of this path is called the Larmor radius.

The angular frequency of this circular motion is determined by equating the Lorentz force to the centripetal force: $q v B = \frac{m v^2}{r}$. Rearranging this equation gives $r = \frac{mv}{qB}$. The angular frequency is then $\omega = \frac{v}{r} = \frac{qB}{m}$. The cyclotron frequency, $f_c$, is related to the angular frequency by $f_c = \frac{\omega}{2\pi}$, so $f_{ci} = \frac{qB}{2\pi m}$.

The ion cyclotron frequency is a fundamental parameter in plasma physics and is crucial for understanding various plasma phenomena, including wave propagation, particle acceleration, and confinement in magnetic fields. It is also the principle behind ion cyclotron resonance heating (ICRH) techniques used to heat plasmas in fusion devices and in certain mass spectrometry applications. The frequency depends on the specific type of ion (its charge-to-mass ratio) and the strength of the magnetic field.