Study of two interacting interplanetary coronal mass ejections encountered by Solar Orbiter during its first perihelion passage

Abstract

Context. Solar Orbiter, the new-generation mission dedicated to solar and heliospheric exploration, was successfully launched on February 10, 2020, 04:03 UTC from Cape Canaveral. During its first perihelion passage in June 2020, two successive interplanetary coronal mass ejections (ICMEs), propagating along the heliospheric current sheet (HCS), impacted the spacecraft. Aims. This paper addresses the investigation of the ICMEs encountered by Solar Orbiter on June 7−8, 2020, from both an observational and a modeling perspective. The aim is to provide a full description of those events, their mutual interaction, and their coupling with the ambient solar wind and the HCS. Methods. Data acquired by the MAG magnetometer, the Energetic Particle Detector suite, and the Radio and Plasma Waves instrument are used to provide information on the ICMEs’ magnetic topology configuration, their magnetic connectivity to the Sun, and insights into the heliospheric plasma environment where they travel, respectively. On the modeling side, the Heliospheric Upwind eXtrapolation model, the 3D COronal Rope Ejection technique, and the EUropean Heliospheric FORecasting Information Asset (EUHFORIA) tool are used to complement Solar Orbiter observations of the ambient solar wind and ICMEs, and to simulate the evolution and interaction of the ejecta in the inner heliosphere, respectively. Results. Both data analysis and numerical simulations indicate that the passage of two distinct, dynamically and magnetically interacting (via magnetic reconnection processes) ICMEs at Solar Orbiter is a possible scenario, supported by the numerous similarities between EUHFORIA time series at Solar Orbiter and Solar Orbiter data. Conclusions. The combination of in situ measurements and numerical simulations (together with remote sensing observations of the corona and inner heliosphere) will significantly lead to a deeper understanding of the physical processes occurring during the CME-CME interaction.

Observation of Kinetic Alfvén Waves inside an Interplanetary Coronal Mass Ejection Magnetic Cloud at 1 au

“…However, it has become evident that their morphology can be influenced by a variety of factors, including the deceleration processes of ICMEs, their interactions with the fast and slow ambient solar wind, and the interactions of multiple ICMEs. Thus, ICMEs exhibit a dynamic nature, often undergoing deformation, deflection, and fragmentation as they traverse the interplanetary medium (Telloni et al 2021). These structural transformations not only alter their visual appearance but also set in motion a cascade of events.…”

On the Role of Alfvénic Fluctuations as Mediators of Coherence within Interplanetary Coronal Mass Ejections: Investigation of Multi-spacecraft Measurements at 1 au

“…where E v (k, t) and E B (k, t) are the sum of the power of the wavelet transforms (Torrence & Compo 1998) of the components of the velocity v(t) and magnetic field B(t) vectors, respectively (Telloni et al 2012(Telloni et al , 2013Good et al 2020Good et al , 2022Telloni et al 2021), and are functions of time t and of the wavenumber k. Here, σ r (k, t) measures the imbalance between the kinetic and magnetic energies, and it is expected to be close to zero in a reference frame comoving with the solar wind due to the equipartition of magnetic and kinetic energy of AFs. This method enables us to investigate large periods of data through visual inspection across wide frequency ranges.…”

Multi-spacecraft study of the solar wind at solar minimum: Dependence on latitude and transient outflows

“…The most complex of these events was SO_2006ZS, labelled in Figs. 1 and 2 combination of two CMEs, a CIR and a HCS crossing, which is investigated in detail by Telloni et al (2021).…”