At lower latitudes our calculations do not capture observed values well. Fig. 6 shows that exospheric temperatures decrease from around 450 K near the pole to around 180 K near the equator. Voyager 2 UVS occultations of δ-Sco suggested an exospheric temperature of 420 ± 30 K near 29.5°N (Smith et al., 1983), while a recent reanalysis of Voyager UVS data inferred a value of 488 ± 14 K (Vervack and Moses, 2012). These and other observations suggest low and mid-latitude exospheric temperatures on Saturn to be of the order of 450 K, roughly twice the value shown in Fig. 6. Our model is presently unable to reproduce observed low and mid-latitude exospheric temperatures on Saturn, illustrating that magnetospheric energy is not being transported from the polar to the equatorial regions. This is related to Saturn’s fast rotation rate and the sub-corotation of the auroral thermosphere, which ultimately generates a meridional wind transporting energy from equator to pole in the deep atmosphere, thus cooling down the equatorial regions (Smith et al., 2007). However, since this study is concerned with polar temperatures only we will defer discussion of the equatorial temperature problem to future investigations.
exospheric temperatures
around 450 K
K
exospheric temperatures
around 180 K
K
exospheric temperature
420 ± 30 K
K
29.5°N
°N
exospheric temperature
488 ± 14 K
K
low and mid-latitude exospheric temperatures
of the order of 450 K
K