cyclotron instability

The cyclotron instability is a process that contributes to the decay of a ring current in Earth's geomagnetic field. This instability occurs when an electromagnetic wave, with a frequency close to that at which charged particles gyrate around the field, interacts with these particles.1

In this interaction, the wave gains energy from the particles, causing the particles to scatter and follow magnetic field lines more closely. A series of these scatterings can lead a particle to move directly along a magnetic field line, causing it to be lost from the ring current and enter Earth's atmosphere. This process is significant when the ring current has more particles near the equatorial plane than near the ends of the field lines, a situation created by magnetospheric convection in the inner magnetosphere. The waves involved in this process typically have frequencies between 0.2 and 5 hertz for protons, and much higher frequencies for electrons.1