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

对木星十米波长射电源位置和发射光束结构的研究对于研究发射机制非常重要（卡尔和Desch，1976年;卡尔等人，1983年）。在所谓的Io-B和Io-A风暴期间发生的木星辐射是右旋（RH）圆偏振或椭圆偏振。然而，当在18 MHz附近观测时，Io-C风暴通常是左旋（LH）圆偏振的。通常，一个长时间的风暴将开始于中央子午线经度（CML）的Io-A区，并在Io-C区结束，在这种情况下，偏振方向在过渡区的RH和LH之间来回波动并不罕见。一般认为，Io-B和Io-A辐射是以非常（X）模式从云顶以上的高度上的连续的Io激发的通量管中发射的，在云顶上的波频率仅略高于电子回旋频率。由于已知木星的近偶极磁场的场线是从木星的北方极区指向木星的南方极区，因此，RH极化的Io-B和Io-A发射来自于靠近Io激励的通量管的北方而不是南方脚。问题是LH极化的Io-C发射来自哪里？利用我们的双偏振干涉仪，我们期望能够测量LH偏振和RH偏振爆发源的角间距，这些爆发发生在彼此的几秒钟内，具有足够的精度来确定它们是否位于相同或相反的极半球。

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.