An instrument carried on the Galileo spacecraft that measures the properties of varying electric fields at frequencies of 5–5.6 MHz and magnetic fields at 5–160 kHz in the atmosphere of Jupiter. Plasma particles are bound to the magnetic field, and motions within the plasma perturb the electric and magnetic fields around them producing changes known as ‘plasma waves’. Scientists use the PWS to investigate the way plasma waves and radio emissions control the scattering and/or loss of trapped radiation in the jovian atmosphere, and to derive fundamental plasma parameters, such as electron density.