Magnetic pulsations are

extremely low frequency Extremely low frequency (ELF) is the ITU designation for electromagnetic radiation (radio waves) with frequencies from 3 to 30 Hz, and corresponding wavelengths of 100,000 to 10,000 kilometers, respectively. In atmospheric sc ...

disturbances in the Earth's

magnetosphere In astronomy and planetary science, a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field. It is created by a celestial body with an active interior Dynamo ...

driven by its interactions with the

solar wind The solar wind is a stream of charged particles released from the Sun's outermost atmospheric layer, the Stellar corona, corona. This Plasma (physics), plasma mostly consists of electrons, protons and alpha particles with kinetic energy betwee ...

. These variations in the planet's magnetic field can oscillate for multiple hours when a

driving force strikes a resonance. This is a form of

Kelvin–Helmholtz instability The Kelvin–Helmholtz instability (after Lord Kelvin and Hermann von Helmholtz) is a fluid instability that occurs when there is shear velocity, velocity shear in a single continuum mechanics, continuous fluid or a velocity difference across t ...

. The intensity, frequency, and orientation of these variations is measured by

Intermagnet The International Real-time Magnetic Observatory Network (INTERMAGNET) is a world-wide consortium of institutes operating ground-based magnetometers recording the absolute level of the Earth's time-varying magnetic field, to an agreed set of stan ...

. In 1964, the

International Association of Geomagnetism and Aeronomy The International Association of Geomagnetism and Aeronomy (IAGA) is an international scientific association that focuses on the study of terrestrial and planetary magnetism and space physics. IAGA is one of the eight associations of the Interna ...

(IAGA) proposed a classification of magnetic pulsations into continuous pulsations (Pc) and irregular pulsations (Pi).

References

Magnetospheres Magnetism in astronomy Earth Solar phenomena {{Astronomy-stub