Abstract
Abstract. The atmosphere of Saturn's largest moon Titan is driven by photochemistry, charged particle precipitation from Saturn's upstream magnetosphere, and presumably by the diffusion of the magnetospheric field into the outer ionosphere, amongst other processes. Ion pickup, controlled by the upstream convection electric field, plays a role in the loss of this atmosphere. The interaction of Titan with Saturn's magnetosphere results in the formation of a flow-induced magnetosphere. The upstream magnetoplasma environment of Titan is a complex and highly variable system and significant quasi-periodic modulations of the plasma in this region of Saturn's magnetosphere have been reported. In this paper we quantitatively investigate the effect of these quasi-periodic modulations on the convection electric field at Titan. We show that the electric field can be significantly perturbed away from the nominal radial orientation inferred from Voyager 1 observations, and demonstrate that upstream categorisation schemes must be used with care when undertaking quantitative studies of Titan's magnetospheric interaction, particularly where assumptions regarding the orientation of the convection electric field are made.
Highlights
Titan is Saturn’s largest moon and the only moon in the solar system known to have a thick atmosphere with an extended exosphere
This is because the equations for Eρ and Eφ are modulated by uz and swap sign when the plasma sheet is moving in a different direction
In this paper we have theoretically examined the effects of magnetodisc flapping on the convection electric field at Titan
Summary
Titan is Saturn’s largest moon and the only moon in the solar system known to have a thick atmosphere with an extended exosphere. A number of authors have attempted to classify the upstream environment of Titan (Rymer et al, 2009; Simon et al, 2010a; Garnier et al, 2010) using a variety of criteria to produce categories such as “plasma sheet”, “current sheet” and “lobe” These classifications have proven to be useful in understanding flyby-to-flyby variability of Titan’s atmosphere (e.g., Westlake et al, 2011). We refer these results to previously established classification schemes and show that classifying Titan’s upstream environment as “current-sheet” does not guarantee a particular orientation of the electric field These results are of relevance in trying to understand the dynamics and evolution of Titan’s atmosphere (e.g., Johnson et al, 2009; Sittler et al, 2009) and for interpreting spacecraft data near Titan (e.g., Simon et al, 2007)
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