A Catalog of Interplanetary Coronal Mass Ejections Observed by Juno between 1 and 5.4 AU

TL;DR

This study catalogs 80 interplanetary coronal mass ejections observed by Juno between 1 and 5.4 AU, analyzing their magnetic properties and expansion behavior to improve understanding of their evolution in the heliosphere.

Contribution

It provides the first comprehensive ICME catalog from Juno data beyond 1 AU and compares expansion rates with other datasets, advancing knowledge of ICME evolution.

Findings

Magnetic flux rope strength decreases with distance as r^{-1.24}

ICME expansion rates differ inside and beyond 1 AU

Juno catalog enables future multispacecraft ICME studies

Abstract

We use magnetic field measurements by the Juno spacecraft to catalog and investigate interplanetary coronal mass ejections (ICMEs) beyond 1 AU. During its cruise phase, Juno spent about 5 years in the solar wind between 2011 September and 2016 June, providing measurements of the interplanetary magnetic field (IMF) between 1 and 5.4 AU. Juno therefore presents the most recent opportunity for a statistical analysis of ICME properties beyond 1 AU since the Ulysses mission (1990-2009). Our catalog includes 80 such ICME events, 32 of which contain associated flux-rope-like structures. We find that the dependency of the mean magnetic field strength of the magnetic flux ropes decreases with heliocentric distance as $r^{-1.24 \pm 0.43}$ between 1 and 5.4 AU, in good agreement with previous relationships calculated using ICME catalogs at Ulysses. We combine the Juno catalog with the HELCATS catalog to create a dataset of ICMEs covering 0.3-5.4 AU. Using a linear regression model to fit the combined dataset on a double-logarithmic plot, we find that there is a clear difference between global expansion rates for ICMEs observed at lesser heliocentric distances and those observed farther out beyond 1 AU. The cataloged ICMEs at Juno present a good basis for future multispacecraft studies of ICME evolution between the inner heliosphere, 1 AU, and beyond.