The Interaction of Successive Coronal Mass Ejections: A Review

Abstract

We present a review of the different aspects associated with the interaction of successive coronal mass ejections (CMEs) in the corona and inner heliosphere, focusing on the initiation of series of CMEs, their interaction in the heliosphere, the particle acceleration associated with successive CMEs, and the effect of compound events on Earth's magnetosphere. The two main mechanisms resulting in the eruption of series of CMEs are sympathetic eruptions, when one eruption triggers another, and homologous eruptions, when a series of similar eruptions originates from one active region. CME-CME interaction may also be associated with two unrelated eruptions. The interaction of successive CMEs has been observed remotely in coronagraphs (with the Large Angle and Spectrometric Coronagraph Experiment -LASCO-since the early 2000s) and heliospheric imagers (since the late 2000s), and inferred from in situ measurements, starting with early measurements in the 1970s. The interaction of two or more CMEs is associated with complex phenomena, including magnetic reconnection, momentum exchange, the propagation of a fast magnetosonic shock through a magnetic ejecta, and changes in the CME expansion. The presence of a preceding CME a few hours before a fast eruption has been found to be connected with higher fluxes of solar energetic particles (SEPs), while CME-CME interaction occurring in the corona is often associated with unusual radio bursts, indicating electron acceleration. Higher suprathermal population, enhanced turbulence and wave activity, stronger shocks, and shock-shock or shock-CME interaction have been proposed as potential physical mechanisms to explain the observed associated SEP events. When measured in situ, CME-CME interaction may be associated with relatively well organized multiple-magnetic cloud events, instances of shocks propagating through a previous magnetic ejecta or more complex ejecta, when the characteristics of the individual eruptions cannot be easily distinguished. CME-CME interaction is associated with some of the most intense recorded geomagnetic storms. The compression of a CME by another and the propagation of a shock inside a magnetic ejecta can lead to extreme values of the southward magnetic field component, sometimes associated with large values of the dynamic pressure. This can result in intense geomagnetic storms, but also trigger substorms and large earthward motions of the magnetopause, potentially associated with changes in the outer radiation belts. Future in situ measurements in the inner heliosphere by Solar Probe+ and Solar Orbiter may shed light on the evolution of CMEs as they interact, by providing opportunities for conjunction and evolutionary studies.

Coronal mass ejections and their sheath regions in interplanetary space

“…As stated by Burlaga et al (2002) merging is a nonlinear and irreversible process, where memory of the source conditions is lost. The merging takes place due to magnetic reconnection between the consecutive CMEs (see Lugaz et al 2017, and references therein). Figure 29 shows an example of a complex ejecta observed during September Fig.…”

An Insight into Space Weather

“…ICMEs are always accompanied by solar winds. Interplanetary propagation of CMEs face aerodynamic drag by solar winds and are accelerated or decelerated on the basis of their relative speed with respect to solar wind i.e., the CMEs which are faster than the solar wind are decelerated while the one which has lower speed is accelerated [12], [30] - [33]. The acceleration of CME solely depends on their interaction with solar wind.…”

“…The acceleration of CME solely depends on their interaction with solar wind. Since the acceleration of CME largely depends on the amount of energy present at the trigger point, there can be an interaction between two CMEs (which were erupted at different times) and due to this their configuration changes [33]. CME also accelerates the energetic particles emanating from the Sun towards the interplanetary space.…”

On the Collision Nature of Two Coronal Mass Ejections: A Review

“…Gopalswamy et al, 2009;Xiong, Zheng, and Wang, 2009;Temmer et al, , 2014Shen et al, 2012a;Liu et al, , 2014Martínez-Oliveros et al, 2012;Webb et al, 2013;Shen et al, 2011Shen et al, , 2012bShen et al, , 2013Shen et al, , 2016Mishra and Srivastava, 2014;Mishra, Srivastava, and Chakrabarty, 2015;Mishra, Srivastava, and Singh, 2015;Mishra, Wang, and Srivastava, 2016;Shanmugaraju et al, 2014;Colaninno and Vourlidas, 2015). A comprehensive review about the interaction of successive CMEs and consequences in particle acceleration and geoeffectiveness by Lugaz et al (2017) can be found in the Topical Collection called Earth-affecting Solar Transients.…”