Titan's tail structure: the multi-instrument study as observed by Cassini

Titan’s  magnetotail is formed as a result of the interaction of Saturn’s magnetospheric flow with Titan’s ionosphere. While the ionosphere is created mainly by EUV radiation and impinging magnetospheric particles on the atmosphere, the tail is more governed by plasma outflow processes, the upstream magnetospheric flow properties (density, flow velocity) and the upstream magnetic field direction. The properties of Titan’s tail has previously been studied with both numerical simulations and in-situ measurements. For instance,  the escape rate has been shown to be of the order  of order ~10²⁴ s^-1, and case studies have revealed a highly dynamic tail structure.

In this work we make an attempt to combine observations of electrons and ions in Titan’s tail for all of the Cassini flybys. We use the Langmuir probe (RPWS/LP) and the Cassini Plasma Spectrometer (CAPS) ion and electron measurements. We put a spatial constraint on the tail’s geometry  and its orientation based on the measurements of electron and ion densities. The estimation of escape rate is revisited, and different sources of variability and their impact on the tail structure are discussed. Furthermore, the link between the convectional electric field E = -v×B and the electron densities distribution is studied. The interim result is that the electron density tends to have higher densities in the hemisphere of positive upstream electric field. This is observed in the altitudes below the dynamo region, which is the chemistry-dominated region. The explanation of the observed distribution tendency is discussed.