SEARCH FOR EFFECTS OF COMET-S-L-9 FRAGMENT IMPACTS ON LOW RADIO-FREQUENCY EMISSION FROM JUPITER

Decametric radio observations of Jupiter were made before, during, and after the impacts of the fragments of the comet S-L 9 with the planet , from the University of Florida Radio Observatory, the Maipu Radio As tronomy Observatory of the University of Chile, and the Owens Valley R adio Observatory of the California Institute of Technology. The decame tric radiation was monitored at frequencies from 16.7 to 32 MHz. The m inimum detectable flux densities were on the order of 30 kJy, except f or that of the large 26.3 MHz array in Florida, which was about 1 kJy. There was no significant enhancement or suppression of the decametric L-burst or S-burst emission with respect to normal activity patterns that might be attributed to the fragment entries. However, a burst of left-hand elliptically polarized radiation having a considerably longe r duration than an L-burst was observed almost simultaneously with the impact of the large fragment Q2, and another with right-hand elliptic al polarization was observed simultaneously with Q1. We consider the p ossibility that these two bursts were emitted just above the local ele ctron cyclotron frequencies from the southern and northern ends, respe ctively, of magnetic flux tubes that had been excited in some way by t he proximity of fragments Q2 and Q1. In addition to the monitoring of the decametric radiation, a search was conducted for possible comet-en hanced Jovian synchrotron radiation at 45 MHz using a large dipole ant enna array at the observatory in Chile, This frequency is above the cu toff of the decametric radiation, but is considerably below the lowest frequency at which the synchrotron emission has previously been detec ted. The minimum detectable flux density with the 45 MHz antenna was a bout 5 Jy. No synchrotron emission at all was found before, during, or after the entry of the comet fragments.