An Interferometric Study of Jupiter's Decimeter Radio Emission

Abstract

An interferometric study of the decimeter radio emission from the planet Jupiter has recently been carried out at the Owens Valley Radio Observatory. Using the two 90-foot paraboloids as an interference polarimeter, observations have been made with various east-west spacings ranging from 300 to 4700 at 104 cm and 300 to 2300 at 21.2 cm and also with some critical north-south spacings at 10.6 cm. The visibility functions obtained are in agreement with earlier measurements, which gave the polar and equatorial dimensions as 1 and 3 planetary diameters, respectively, but they are more complete and extend to larger base lines. They permit the fitting of a rather detailed model for the decimeter brightness distribution. The observations are consistent with a symmetrical synchrotron emission source having the polarization properties one would expect with a dipole magnetic field. It probably is centered quite closely on the planetary disk, which is itself seen as a thermal radio source. The observations also indicate the presence of a small circularly polarized component in the radiation which varies in magnitude and sense as Jupiter rotates. The disk emission at 10.4 cm is about twice the thermal emission one would expect for a temperature of 130 K. The implications of the various results are discussed.