Investigatin of the origin of Jupiter's aurora : in coordination with distant-encounter of Ulysses

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We have investigated the correlation between the solar wind parameters and integrated flux of Jupiter's infrared aurora to find out if they show "positive" or "negative" correlation. In the past, observers suggested "positive" correlations (weak, though), and on the other hand, theoretists proposed models which expect negative correlations between the solar wind and Jupiter's auroral response. This study is to clarify the case using observations and simulations.The solar wind parameters have been determined based on MHD tomography analysis of interplanetary scintillations which are measured at 4 observing sites in Japan. Parameters on interplanetary magnetic field (IMF) have also been determined. Jupiter data have been selected from our archives and 4 data sets (acquired in 1998-2000) were compared with the solar-wind data.Our conclusions include :(1) Two data sets, each of which has many nights of Jupiter observations, indicate a good "positive" correlation with the solar-wind ram pressure.(2) One data set is indicative of "negative" correlation, however, it includes only 2 nights of Jupiter observations, and lack of IPS measurements just before this period prevents us from solid conclusions. Another set shows nearly constant aurora brightness in spite of a dramatic increase of the solar-wind ram pressure.(3) Among all of 4 data sets, the aurora brightness can be clearly divided in 2 groups : the first one is "brighter" aurora and is associated to northward IMF, and the second one is "dimmer" aurora associated to southward IMF. Such relationship is consistent with the fact that Jupiter's magnetic field has an opposite polarity compared to the Earth's one.The last conclusion in the above (correlation with IMF polarity) is the most important and is for the first time indicated based on the observations. With such useful tools, developed through this study, we should be able to continue increasing our knowledge about the solar-wind magnetosphere interactions.