Plasma environment in the wake of Titan from hybrid simulation: A case study

Abstract

[1] On 26 December 2005, the Cassini spacecraft flew through Titan's plasma wake and revealed a complex and dynamic region. Observations suggest a strong asymmetry which seems to be displaced from the ideal position of the wake. Two distinct plasma regions are identified with a significant difference on the electron number density and on the plasma composition. Simulation results using a threedimensional and multi-species hybrid model, performed in conditions similar to those encountered during the flyby, are presented and compared to the observations. An acceptable agreement is shown between the model predictions and the observations. We suggest that the observed asymmetries, in terms of density and plasma composition, are mainly caused by the a combination of the asymmetry in the ion/electron production rate and the magnetic field morphology, where the first plasma region is connected to the dayside hemisphere of Titan's ionosphere while the other is connected to the nightside hemisphere. Citation: Modolo, R.,

The orientation of Titan’s dayside ionosphere and its effects on Titan’s plasma interaction

“…Using Cassini observations Wahlund et al (2005) report a net ion loss rate of 1 × 10 25 s −1 . Later estimates by Modolo et al (2007) A further increase in the loss rate could occur if the electron impact ionization rates were increased. The electron impact rates used in this study are based on the CAPS electron fluxes measured during the TA encounter.…”

“…Understanding the magnetospheric variability is crucial to understanding Titan's interaction. Asymmetries in the observed ion densities and composition downstream of Titan during the T9 flyby were attributed by Modolo et al (2007) as being due to the variability in the magnetic field morphology.…”

“…Bertucci et al, 2009). This variability was found to be crucial to understanding aspects of the T9 observations by Modolo et al (2007). After the Voyager encounter the magnetic field was thought to be nearly perpendicular to Titan's orbital plane throughout the orbit.…”

“…Self-consistent hybrid simulations (kinetic ions, fluid electrons) have been carried to account for the ion gyroradii effects near Titan (e.g. Brecht et Ledvina et al, 2004a;Sillanpää et al, 2006;Simon et al, 2006;Modolo et al, 2007;Müller et al, 2010). The major limitation to the hybrid simulation performed to date has been their lack of any description of the ionosphere.…”

Modeling of Venus, Mars, and Titan

“…However, the Hall MHD model still simulates all ions as a single fluid, which averages out the dynamics of ionospheric ions and ions from Saturn's magnetosphere. Therefore, the model was not able to reproduce the two compositionally distinct ion tails like the hybrid model of Modolo et al (2007).…”