Conductivities of Titan's dusty ionosphere

Abstract

Titan is immersed in Saturn's magnetosphere (Bertucci et al., 2008;Garnier et al., 2010) and does not have its own magnetic field. Instead, an induced magnetic field is formed around Titan from the interactions with Saturn's magnetosphere (Wahlund et al., 2005), similarly to interactions of Venus and Mars with the solar wind and interplanetary magnetic field (e.g., Bertucci et al., 2011 and references therein). The interaction between Titan and the ambient magnetic field depends to a large degree on Titan's conductive ionosphere. Previously, the electrical properties of Titan's ionosphere were derived using only the ion and electron content (Rosenqvist et al., 2009). In the later years, the data sets have been significantly updated. Most notably, large amounts of charged dust were detected in Titan's ionosphere (Ågren et al., 2012;Coates et al., 2007;Shebanits et al., 2013) and a globally present dusty ion-ion plasma is expected (Shebanits et al., 2016). The charged dust grains in the ionosphere-like plasma of Enceladus plume (Morooka et al., 2011) and in the near-equatorial dusty ionosphere of Saturn (Morooka et al., 2019) were shown to have a profound effect on its electric conductivities by Simon et al. (2011) and Yaroshenko and Lühr (2016), and Shebanits et al. (2020, respectively. In this work we derive the electrical properties of Titan's ionosphere using the full plasma content: electrons, positive ions and negative ions/dust grains and investigate the impact of dusty plasma on an unmagnetized planetary body. The relevant in-situ measurements used here are from the Radio and Plasma Wave Science Langmuir Probe (RPWS/LP, Gurnett et al., 2004), the Ion and Neutral Mass Spectrometer (INMS, Teolis et al., 2015;Waite et al., 2004) and the Cassini Fluxgate Magnetometer (MAG, Dougherty et al., 2004). The data set spans the entire Cassini mission and is representative of a full solar cycle and nearly half Titan year.