THE JOVIAN LEFT HAND POLARIZED RADIATION

Very few studies have been made of Jupiter's left-hand polarized (LH) emission. Here we investigate in detail the LH emission from 2.8 MHz t o 40 MHz by analysing the Voyager Planetary Radio Experiment (PRA) dat a during the two months when the spacecraft were close to Jupiter. We consider separately the observations by Voyager 1 and Voyager 2, befor e and after closest approach, in order to study the longitudinal and l atitudinal beaming, and search for any local time effect. The average statistical properties of the LH radiation are contrasted to the RH on e which is better known. The main findings can be summarized as follow s: 1) The occurrence probability of the RH emission is about the same as the LH at frequencies less than 5 MHz, and a maximum of probability is found at about 8 MHz. 2) At frequencies above 15 MHz the LH probab ility decreases dramatically. 3) The probability spectra in CML of bot h RH and LH show a continuity from low to high frequencies. 4) In the low frequency range, below about 10 MHz, the occurrence pattems are ve ry simple and the RH pattem is complementary to the LH one: RH radiati on occurs mainly from 150-degrees to 300-degrees CML, and LH radiation from 310-degrees to 110-degrees. 5) At higher frequencies the two pat tems become complex. 6) The probability spectra in lo phase show that the Io-related peaks exist in both RH and LH emission at 90-120-degree s and at 240-300-degrees, and that they extend to the lowest frequency , 2.5 MHz. 7) The latitude effect is mainly significant for the RH emi ssion where it modifies the shape of the main peaks. 8) The local time affects the probability spectrum: the probability drops significantly after closest approach for both RH and LH emission. We interpret thes e results in terms of beaming of the radiation in hollow cones, i.e. o n the surface of conical sheets of large opening angle, 50-degrees to 80-degrees. For the emission at f less than or similar to 10 MHz, thes e conical sheets are in polar regions, L almost-equal-to 6 to 10, at R greater than or similar to 1.4 R(J) where the field is more dipolar t han at lower altitudes (and higher frequencies), and they are active a t all longitudes. An observer near the plane of the ecliptic in the he misphere centered on longitude 200-degrees (20-degrees) is located alo ng the surface of at least one of the cones of the northem (southem) a uroral zone and receives RH (LH) radiation. For the lo-related radiati on at higher frequencies, greater than or similar to 20 MHz, the situa tion is similar except that conical sheets are activated by lo in only a small range of longitudes.