3:30 PM - 4:45 PM
[PCG21-P17] North-south asymmetry of Saturn's auroral radio emissions: The seasonal variation of their fluxes
Keywords:Saturn, SKR(Saturn kilometric radiation), North-south activity ratio, seasonal variation, Cassini
In this study, we extend the study in Kimura et al. (2013) to 2015 covering the northern summer. We note that the simple extension of the analysis period is hard because of the Cassini orbit bias. Since the SKR is stronger in the dawn side, Kimura et al. (2013) adopted the detection criteria that Cassini is at the dawn side (2h - 10h LT). And in order to avoid the visibility effect of SKR caused by its propagation, other selection criteria were also set in the latitude (-5 to +30deg (RH), +5 to -30 (LH)) and the distance from Saturn (10 - 100 Rs). However, because of Cassini’s apokrone after 2010 was gradually shifted from dawn to dusk, it becomes hard to get a large number of observations under the same criteria.
In this study, we kept the same latitude and distance criteria but used the all LT data set. But, at former we could see the different LT between the both SKR, so we couldn’t avoid the LT dependence. In parallel, at latter we selected +-5deg in the latitude and verified the result about the data observed simultaneously for the north and south. In this revised result, the intensity of LH component in 2004-2009 (south, summer) was stronger ~+40 than RH (north, winter). In 2010-2012, the both SKR intensities got close to each other. After 2013, RH (north, summer) was stronger by ~+20 than LH (south, winter). These results support the result in Kimura et al. (2013) that the summer hemisphere is more enhanced. The variation of SKR peak intensity by a running median with a window of +-35 days to avoid visibility effect also showed same trend. However, it is not well explained that the flux ratio was more than 10 in southern summer but only 0.2-0.4 in northern summer. In this presentation, we will also show the correlation of these trends to the SKR rotational period, solar EUV activity, etc. (Cassini Solstice Mission will be finished in Sep. 2017.)