Titan interaction with the supersonic solar wind

TL;DR

This paper reports Cassini's observations of Titan's interaction with the supersonic solar wind, revealing a collisionless bow shock and induced magnetosphere similar to unmagnetized planets, with implications for bodies like Pluto.

Contribution

First direct observation of Titan's interaction with the supersonic solar wind, showing features akin to unmagnetized planets in the outer solar system.

Findings

Detection of a collisionless, supercritical bow shock.

Observation of a well-defined induced magnetosphere.

Plasma density enhancements indicating plasma clouds or streamers.

Abstract

After 9 years in the Saturn system, the Cassini spacecraft finally observed Titan in the supersonic solar wind. These unique observations reveal that Titan interaction with the solar wind is in many ways similar to un-magnetized planets Mars and Venus in spite of the differences in the properties of the solar plasma in the outer solar system. In particular, Cassini detected a collisionless, supercritical bow shock and a well-defined induced magnetosphere filled with mass-loaded interplanetary magnetic field lines, which drape around Titan ionosphere. Although the flyby altitude may not allow the detection of an ionopause, Cassini reports enhancements of plasma density compatible with plasma clouds or streamers in the flanks of its induced magnetosphere or due to an expansion of the induced magnetosphere. Because of the upstream conditions, these observations are also relevant for unmagnetized bodies in the outer solar system such as Pluto, where kinetic processes are expected to dominate.