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

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 yr 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±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 data set of ICMEs covering 0.3–5.4 au. Using a linear regression model to fit the combined data set on a double-logarithmic plot, we find that there is a clear difference between global expansion rates for ICMEs observed at shorter 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.

On the utility of flux rope models for CME magnetic structure below 30Rs

“…Since magnetic field hodograms are increasingly being used in the analysis of in-situ ICME observations (e.g. Nieves-Chinchilla et al, 2019;Scolini et al, 2022;Davies et al, 2021), including recent PSP events (e.g. Nieves-Chinchilla et al, 2020;Winslow et al, 2021), we constructed hodogram visualizations of both the MHD simulation data and the in-situ flux rope model fits to further evaluate the quality of the flux rope model reconstructions.…”

Multi-Spacecraft Observations of the Evolution of Interplanetary Coronal Mass Ejections Between 0.3 and 2.2 AU: Conjunctions with the Juno Spacecraft

“…In this study, we make use of the catalogue of ICMEs identified at Juno during its cruise phase in Davies et al (2021a). The catalogue identified ICME signatures observed in measurements of the magnetic field taken by the Juno Magnetic Field Investigation instrument (MAG; Connerney et al 2017).…”

“…This way, we have attempted to identify in the Juno data all ICMEs identified within 1 AU, whether or not they satisfy the strict criteria described above for which we created our Juno catalogue. We identify an additional 7 ICMEs this way which were not in our initial catalogue as published in Davies et al (2021a).…”

“…Once the potential links between spacecraft within 1 AU and Juno had been established, we attempt to match features in the magnetic field data. With only magnetic field data available during the Juno cruise phase, defining ICME and magnetic ejecta boundaries presented in the Juno ICME catalogue is not straightforward; only magnetic flux-rope-like structures were considered as magnetic ejecta in the analysis of event properties in Davies et al (2021a). However, with plasma data available at ACE, Wind and STEREO-A/B, periods of magnetic ejecta can be more confidently defined at these spacecraft; the ICME catalogues of Richardson & Cane (2010), Jian et al (2018), andNieves-Chinchilla et al (2018) identify regions of low proton temperature to be a reliable indication of magnetic ejecta as well as other plasma signatures (see Zurbuchen & Richardson 2006).…”

“…In this study, we use the Davies et al (2021a) catalogue of ICMEs observed by Juno to compile a database of events also observed by other spacecraft at, or within, 1 AU (MESSENGER, Venus Express, STEREO, or Wind/ACE). Section 2 presents the methodology used to identify ICME events observed by two or more spacecraft, and Section 3 provides a description of the multispacecraft event catalogue and an overview of the separations between observing spacecraft.…”