Guiding center

In physics, the motion of an electrically charged particle (such as an electron or ion in a plasma) in a magnetic field can be treated as the superposition of a relatively fast circular motion around a point called the guiding center and a relatively slow drift of this point. The drift speeds may differ for various species depending on their charge states, masses, or temperatures, possibly resulting in electric currents or chemical separation.

If the magnetic field is uniform and all other forces are absent, then the Lorentz force will cause a particle to undergo a constant acceleration perpendicular to both the particle velocity and the magnetic field. This does not affect particle motion parallel to the magnetic field, but results in circular motion at constant speed in the plane perpendicular to the magnetic field. This circular motion is known as the gyromotion. For a particle with mass ${\displaystyle m}$ and charge ${\displaystyle q}$ moving in a magnetic field with strength ${\displaystyle B}$, it has a frequency, called the gyrofrequency or cyclotron frequency, of

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