Multipoint Observations of the June 2012 Interacting Interplanetary Flux Ropes

Abstract

We report a detailed analysis of interplanetary flux ropes observed at Venus and subsequently at Earth's Lagrange L1 point between June 15 and 17, 2012. The observation points were separated by about 0.28 AU in radial distance and 5 • in heliographic longitude at this time. The flux ropes were associated with three coronal mass ejections (CMEs) that erupted from the Sun on June 12-14, 2012 (SOL2012-06-12, SOL2012-06-13, and SOL2012-06-14). We examine the CME-CME interactions using in-situ observations from the almost radially aligned spacecraft at Venus and Earth, as well as using heliospheric modeling and imagery. The June 14 CME reached the June 13 CME near the orbit of Venus and significant interaction occurred before they both reached Earth. The shock driven by the June 14 CME propagated through the June 13 CME and the two CMEs coalesced, creating the signatures of one large, coherent flux rope at L1. We discuss the origin of the strong interplanetary magnetic fields related to this sequence of events, the complexity of interpreting solar wind observations in the case of multiple interacting CMEs, and the coherence of the flux ropes at different observation points.

CME Magnetic Structure and IMF Preconditioning Affecting SEP Transport

“…Previous studies have shown that a faster shock can indeed travel through a slower, preceding structure (e.g., E. K. J. Kilpua, Good, et al, 2019;Lugaz, Farrugia, Manchester, & Schwadron, 2013). A possible 'interface' between the preceding interplanetary structure and the following sheath region driven by the 2012 May 11 CME is indicated by a dashed vertical line in Figure 8 (estimated via the rapid change in direction in the magnetic field Z-component).…”

On the Radial and Longitudinal Variation of a Magnetic Cloud: ACE, Wind, ARTEMIS and Juno Observations

“…These solutions assume a force-free magnetic field with a constant α in a cylindrical configuration, where J 0 and J 1 are the zeroth and first order Bessel functions, B 0 is the magnetic field strength along the axis, and r is the radial distance from the rope axis. The magnetic field solutions were fitted to the data of ACE, Wind, THEMIS B, THEMIS C, and Juno using a least squares procedure similar to that developed by Lepping, Jones, and Burlaga (1990) where the calculated MVA orientation initialises the χ 2 minimisation; details of this technique are given in Good et al (2019) and Kilpua et al (2019). The other flux rope fitting method used considers the magnetic field to have a uniform twist across the rope cross-section: a 'Gold-Hoyle' tube (Gold and Hoyle, 1960).…”

“…Studies that describe such encounters to analyse ICME evolution include Burlaga et al (1981), Cane, Richardson, and Wibberenz (1997), Bothmer and Schwenn (1997), Liu et al (2008), Möstl et al (2009a), Möstl et al (2009b), Rouillard et al (2010), Farrugia et al (2011), Nakwacki et al (2011), Kilpua et al (2011), Nieves-Chinchilla et al (2012), Ruffenach et al (2012), Nieves-Chinchilla et al (2013), Good et al (2015)). There have been several case studies (Winslow et al, 2016;Good et al, 2018;Kilpua et al, 2019;Lugaz, Winslow, and Farrugia, 2019) and statistical studies (Good et al, 2019;Vršnak et al, 2019;Salman, Winslow, and Lugaz, 2020) that have greatly expanded the number of analysed events in recent times.…”

Editorial: Magnetic Flux Ropes: From the Sun to the Earth and Beyond

“…They concluded that the CME of interest releases heat throughout its journey from the Sun to Earth. Employing spacecrafts orbiting Venus and at the L1 point close to Earth, [Kilpua et al, 2019] found two CMEs coalesce into one coherent flux rope. [Zhao et al, 2019] concluded that the coalescence process between interplanetary CME flux ropes can operate in scales of hundreds of Earth radii and persist for hundreds of minutes.…”

“…In this Research Topic, we also identify two important trends: 1) utilizing high-resolution observations [e.g., Awasthi and Liu, 2019;Wang and Liu, 2019], and 2) integrating observations with models [e.g., Fan and Liu, 2019;Jiang et al, 2019;Kilpua et al, 2019;Mishra et al, 2020]. To further advance our understanding of the origin, structure, and evolution of magnetic flux ropes in the heliosphere, we look forward to observations obtained by next-generation instruments such as the 4-m Daniel K. Inouye Solar Telescope, Parker Solar Probe (PSP), Solar Orbiter, as well as the Advanced Space-based Solar Observatory (ASO-S) that is scheduled to launch in 2022 by China.…”