A Research about the locations of Jupiter's decametric sources by VLBI

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The investigation of Jupiter's decameter-wavelength radio source locations and emission beam structure is very important for the study of the emission mechanism (Carr and Desch, 1976 ; Carr et al., 1983). Jupiter's rediation occurring during the so-called Io-B and Io-A storms is right-hand (RH) circularly or elliptically polarized. The Io-C storms, however, are often left-hand (LH) circularly polarized when observed in the vicinity of 18 MHz. Often a storm of long duration will begin in the Io-A region of central meridian longitude (CML) and end in the Io-C region, in which case it is not uncommon for the polarization sense to fluctuate back and forth between RH and LH in the transition region. It is generally believed that the Io-B and Io-A radiations are emitted in the extraordinary (X) mode, from within successive Io-energized flux tubes at the altitudes above the cloud-tops at which the wave frequency is only slightly higher than the electron gyrofrequency.Since it is known that the field lines of Jupiter's nearly-dipolar magnetic field are directed from the northern to the southern Jovigraphic polar regions, it follows that the RH polarized Io-B and Io-A emissions come from near the northern rather than the southern foot of the Io-energized flux tube. The question is where do the LH polarized Io-C emissions come from? With our dual-polarization interferometer we expect to be able to measure the angular separation of the sources of the LH polarized and RH polarized bursts that occur within a few time seconds of each other with sufficient accuracy to determine whether they were located in the same or in opposite polar hemispheres.