Jack Connerney has participated in magnetic field investigations of every magnetized planet in the solar system, from Mercury, Earth and Mars to Jupiter, Saturn, Uranus, and Neptune. He developed novel techniques for measurement, analysis, and modeling of planetary magnetic fields using both in-situ and remote observations. His >200 scientific publications span several disciplines, including planetary magnetic fields, crustal magnetism, geophysical inverse theory, ionospheres, aurorae, and the electrodynamic interaction of satellites and ring systems with a planetary magnetic field.