Plasma Density Structures at Comet 67P/Churyumov-Gerasimenko

TL;DR

This study analyzes plasma density structures at comet 67P using Rosetta data, revealing pulse-like signatures linked to the comet's plasma boundary, with proximity to the exobase influencing pulse frequency.

Contribution

It provides observational evidence of plasma filaments originating from the diamagnetic cavity boundary, supporting simulation predictions.

Findings

Pulse signatures are observed in plasma density, ion flux, and magnetic field.

Proximity to the electron exobase correlates with increased pulse activity.

Pulses likely originate from the diamagnetic cavity boundary.

Abstract

We present Rosetta RPC case study from four events at various radial distance, phase angle and local time from autumn 2015, just after perihelion of comet 67P/Churyumov-Gerasimenko. Pulse like (high amplitude, up to minutes in time) signatures are seen with several RPC instruments in the plasma density (LAP, MIP), ion energy and flux (ICA) as well as magnetic field intensity (MAG). Furthermore the cometocentric distance relative to the electron exobase is seen to be a good organizing parameter for the measured plasma variations. The closer Rosetta is to this boundary, the more pulses are measured. This is consistent with the pulses being filaments of plasma originating from the diamagnetic cavity boundary as predicted by simulations.