On the basis of radio measurements of Neptune at 20 cm, one can infer the presence of ~0.4 mJy synchrotron radiation. By assuming a dipole-like magnetic field, with the energetic electrons confined to the magnetic equator, we estimate Neptune's magnetic dipole moment to be ~1 G R3N. Its electron population should be between that in Uranus' and Jupiter's magnetospheres. If the electrons are injected by the solar wind, local acceleration processes in the magnetosphere are required to energize the particles, because adiabatic diffusion alone is not sufficient. ¿ American Geophysical Union 1989