Upper Limit to the 11.4 m Flux of Saturn using VLBI

Abstract

Searches continue for non-thermal continuum1,2 and noise storm (ref. 3 and S. Ya. Braude, personal communication) radio emissions from Saturn which might be analogous to the decimetric and decametric emissions from Jupiter4,5. From wavelengths of 1 mm to 3.5 cm the measurements of Saturn can be fitted to a 140 K thermal blackbody curve. From 9 cm to longer wavelengths the equivalent blackbody temperature rises. Yerbury, Condon and Jauncey1 measure a temperature of 400±65 K at 49.5 cm and 540±110 K at 94.3 cm using the Arecibo radio telescope. Observations of thermal emission at longer wavelengths are difficult because of the large collecting areas required. Gulkis2 fits the existing emission curve with a deep, hot model atmosphere. Luthey6, however, considers the possibility of synchrotron radiation as a non-thermal explanation of the rising temperature curve at larger wavelengths. So far the observations of decametric noise storm emissions from Saturn seem to be negative3 although Braude reports possible emissions of several tens of flux units at 25, 20 and 16.7 MHz.