Cassini in Titan's tail: CAPS observations of plasma escape

We present observations of CAPS electron and ion spectra during Titan distant tail crossings at 5,000–10,000 km altitude by the Cassini spacecraft. In common with closer tail encounters, we identify ionospheric plasma in the tail. Some of the electron spectra indicate a direct magnetic connection to Titan's dayside ionosphere due to the presence of ionospheric photoelectrons. Ion observations reveal heavy (m/q∼ 16 and 28) and light (m/q = 1–2) ion populations streaming into the tail. Using the distant tail encounters T9, T75 and T63, we estimate total plasma loss rates from Titan via this process of (4.2, 0.96 and 2.3) × 1024 ions s−1 respectively for the three encounters, values which are in agreement with some simulations but slightly lower than earlier estimates based on non‐differential techniques. Using the mass‐separated data, this corresponds to mass loss rates of (8.9, 1.6, 4.0) × 1025 amu s−1 for T9, T75 and T63 respectively, an average loss rate of ∼7 tonnes per Earth day. Remarkably, all of the tail encounters studied here indicate a split tail feature, indicating that this may be a common feature in Titan's interaction with Saturn's magnetosphere. Key Points Observations in Titan's tail provide ion and mass escape rate Electrons and ions stream away from Titan Split tail seen at the three encounters studied