Alfvén resonator

An Alfvén resonator or Ionosphere Alfvén resonator is a spectral resonance structure found within geomagnetic fields in the frequency range of 0.1–10 Hz.^[1] First reported in 1989, they are ionospheric short-period geomagnetic variations primarily seen as nighttime phenomena and rarely observed during the day.^[2] The nighttime preference is due to lower electrical conductivity in the ionospheric dynamo region, which enables the feedback instability. ^[3]

See also

• Earth–ionosphere waveguide