Small amplitude fluctuations in the Earth’s magnetic field, usually in the frequency range from 0.01 to 3 Hz and usually with amplitudes less than 10 nanotesla. Micropulsations having amplitudes up to tens of nanotesla result from interactions between plasma emitted from the Sun (solar wind) and the Earth’s field. Micropulsations also result from lightning strikes. Micropulsations are classified as continuous (pc), irregular (pi), pearl (pp), etc. Also called pulsations. See also bay, magnetic storm, and Figure M-2.