Abstract
AbstractIn order to analyze varying plasma conditions upstream of Titan, we have combined a physical model of Saturn's plasma disk with a geometrical model of the oscillating current sheet. During modeled oscillation phases where Titan is farthest from the current sheet, the main sources of plasma pressure in the near‐Titan space are the magnetic pressure and, for disturbed conditions, the hot plasma pressure. When Titan is at the center of the sheet, the main sources are the dynamic pressure associated with Saturn's cold, subcorotating plasma and the hot plasma pressure under disturbed conditions. Total pressure at Titan (dynamic plus thermal plus magnetic) typically increases by a factor of up to about 3 as the current sheet center is approached. The predicted incident plasma flow direction deviates from the orbital plane of Titan by ≲10°. These results suggest a correlation between the location of magnetic pressure maxima and the oscillation phase of the plasma sheet. Our model may be used to predict near‐Titan conditions from “far‐field” in situ measurements.
Highlights
Titan is usually embedded within the rotating magnetosphere of Saturn, a configuration which leads to the formation of a “flow-induced” magnetosphere, via the draping of the magnetic field in the subcorotating flow about the moon (Titan’s orbital speed of ∼6 km s−1 is small compared to the typical speed of the rotating plasma, ∼120 km s−1)
The fits to the amplitude and phase of the Bρ and Bφ fields are reasonable, (i) the displayed Bρ data show a change in sign during most oscillations, indicative of passage north of the current sheet plane, which is not reproduced with the model, and (ii) the Bφ fluctuations show a much steeper “rising” part compared to the model, suggesting that the plasma sheet ripple exhibits structure more complex than a sinusoidal form (equation (1))
Our model reproduces some of the large-scale variability in the observed magnetic field, more complex structure for the ripple in the current sheet is required for better agreement
Summary
Titan is usually embedded within the rotating magnetosphere of Saturn, a configuration which leads to the formation of a “flow-induced” magnetosphere, via the draping of the magnetic field in the subcorotating flow about the moon (Titan’s orbital speed of ∼6 km s−1 is small compared to the typical speed of the rotating plasma, ∼120 km s−1). We have combined the A11 model of sheet geometry with the Saturn plasma disk model of Achilleos et al [2010a] (hereafter Ach10), updated by Achilleos et al [2010b], in order to predict the variable magnetic and plasma parameters during the T15 encounter of Titan by the Cassini spacecraft (closest approach occurred on 2 July 2006 at 09:21 UTC, at altitude ∼1900 km). This analysis enables us to predict the variations which arise from plasma sheet oscillations.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
