The birth and growth of a solar wind cavity around a comet -- Rosetta observations

TL;DR

This paper analyzes Rosetta's observations of how a solar wind cavity forms around comet 67P/CG as it approaches the Sun, highlighting the process from initial perturbations to cavity development.

Contribution

It provides a detailed analysis of the formation and growth of the solar wind cavity around a comet, including a geometric model explaining the observations.

Findings

Solar wind cavity forms as comet approaches the Sun.

Discontinuity marks the cavity boundary passing over spacecraft.

Slowdown and heating of solar wind explained by single particle motion.

Abstract

The Rosetta mission provided detailed observations of the growth of a cavity in the solar wind around comet 67P/CG. As the comet approached the Sun, the plasma of cometary origin grew enough in density and size to present an obstacle to the solar wind. Our results demonstrate how the initial slight perturbations of the solar wind prefigure the formation of a solar wind cavity, with a particular interest placed on the discontinuity (solar wind cavity boundary) passing over the spacecraft. The slowing down and heating of the solar wind can be followed and understood in terms of single particle motion. We propose a simple geometric illustration that accounts for the observations, and shows how a cometary magnetosphere is seeded from the gradual steepening of an initially slight solar wind perturbation. A perspective is given concerning the difference between the diamagnetic cavity and the solar wind cavity.