Analysis of Voyager 1 and Voyager 2 in situ CME observations

TL;DR

This study analyzes in-situ observations of ICMEs by Voyager 1 and 2 from 1 to 10 AU, revealing their expansion and internal structure, and demonstrating methods useful for future heliospheric research.

Contribution

It provides a detailed comparison of ICME properties observed by both Voyager spacecraft and introduces methods for analyzing multi-mission heliospheric data.

Findings

ICMEs expand as they propagate outward, with decreasing density and magnetic field strength.

21 common ICME events detected by both Voyager spacecraft.

A case with a clearly detected shock by both spacecraft.

Abstract

This paper studies ICMEs detected by both Voyager spacecraft during propagation from 1 to 10 AU, with observations from 1977 to 1980. ICMEs are detected by using several signatures in the in-situ data, the primary one being the low measured to expected proton temperature ratio. We found 21 events common to both spacecraft and study their internal structure in terms of plasma and magnetic field properties. We find that ICMEs are expanding as they propagate outwards, with decreasing density and magnetic field intensities, in agreement with previous studies. We first carry out a statistical study and then a detailed analysis of each case. Furthermore, we analyse one case in which a shock can be clearly detected by both spacecraft. The methods described here can be interesting for other studies combining data sets from heliospheric missions. Furthermore, they highlight the importance of exploiting useful data from past missions.