Heavy ions, temperatures and winds in Titan's ionosphere: Combined Cassini CAPS and INMS observations

摘要

Multiple Titan encounters by the Cassini spacecraft have shown that ion chemistry in Titan's upper atmosphere is much more complex than previously thought. As well as showing a great variety of species present below 100 amu, they also include the detection of negative ions and of large abundances of ions above 100 amu. Here, we use data from two Cassini instruments, the Cassini plasma spectrometer's ion beam sensor (CAPS/IBS) and the ion and neutral mass spectrometer (INMS) during fourteen Cassini encounters with Titan's upper atmosphere. By simultaneous analysis of the combined data, we are able to determine the ion temperature, one component of the wind speed and spacecraft potential. Using these derived quantities, we are also able to extend the analysis of CAPS/IBS data to quantify the abundance of ions above 100 amu and to statistically estimate their composition.