Particle and field environment of Uranus

Abstract In 1985 the spin axis of Uranus points within 10° of the Sun and the planet's position is very near the solar apex direction. A Uranus mission with an encounter near 1985 might expect to measure the unusual particle and field configuration of a “pole-on” magnetosphere and also properties of the interstellar medium. We give here estimates of the particle and field environment of Uranus based on extrapolation of solar wind data from 1 AU and on scaling relations for an Earth-type magnetosphere. Since the magnetic moment of Uranus is unknown, all magnetospheric parameters are derived as a function of the dipole strength. The onset of special magnetospheric properties are identified as the dipole moment increases from small to large values. A fairly complete set of magnetospheric parameters is given for a specific dipole moment to illustrate the case of a large moment.