The first in situ observation of torsional Alfvén waves during the interaction of large-scale magnetic clouds

Abstract

The large-scale magnetic cloud such as coronal mass ejections (CMEs) is the fundamental driver of the space weather. The interaction of the multiple-CMEs in interplanetary space affects their dynamic evolution and geo-effectiveness. The complex and merged multiple magnetic clouds appear as the insitu signature of the interacting CMEs. The Alfvén waves are speculated to be one of the major possible energy exchange/dissipation mechanism during the interaction. However, no such observational evidence has been found in the literature. The case studies of CME-CME collision events suggest that the magnetic and thermal energy of the CME is converted into the kinetic energy. Moreover, magnetic reconnection process is justified to be responsible for merging of multiple magnetic clouds. Here, we present unambiguous evidence of sunward torsional Alfvén waves in the interacting region after the super-elastic collision of multiple CMEs. The Walén relation is used to confirm the presence of Alfvén waves in the interacting region of multiple CMEs/magnetic clouds. We conclude that Alfvén waves and magnetic reconnection are the possible energy exchange/dissipation mechanisms during large-scale magnetic clouds collisions. The present study has significant implications not only in CME-magnetosphere interactions but also in the interstellar medium where interactions of large-scale magnetic clouds are possible.

Transition to turbulence in nonuniform coronal loops driven by torsional Alfvén waves

“…Aschwanden & Wang (2020) interpreted oscillations in the magnetic energy during solar flares as torsional Alfvén waves. This type of waves has also been reported in the solar wind during the interaction between coronal mass ejections (Raghav & Kule 2018).…”

First Analysis of In Situ Observation of Surface Alfvén Waves in an ICME Flux Rope

“…It is also proposed that they may be triggered by some physical processes happening locally (Bavassano et al 2001;Bruno & Carbone 2013). Recently, we found their existence during CME-CME and CME-HSS interactions, and inside the ICME sheath regions (Raghav & Kule 2018a, 2018bDhamane et al 2022;Raghav et al 2022). Moreover, AWs play a key role in modulating the recovery phase of geomagnetic storms and slowing down the restoration of the magnetosphere toward its pre-storm equilibrium state (Raghav et al 2018(Raghav et al , 2019Shaikh et al 2019b;Choraghe et al 2021;Telloni et al 2021).…”

“…In these waves, ions collectively respond to perturbations in the ambient magnetic field, such that the ions provide inertia, while the magnetic field supplies the required restoring force (Alfvén 1942). The fluid velocity and magnetic field fluctuations propagating in the direction of the magnetic tension force, i.e., well-correlated changes in the respective components of the magnetic field and plasma velocity, lead to the apparent characterization of AWs (Walén 1944;Hudson 1971;Yang & Chao 2013;Raghav & Kule 2018a). In heliospheric plasma, AWs are observed in two forms: arc-polarized Alfvén waves that have often been recognized in the solar wind (Belcher & Davis 1971;Wang et al 2012) and tube modes in ideal magnetic flux ropes, such as the torsional mode (Gosling et al 2010;Raghav et al 2018).…”

Observation of Alfvén Ion Cyclotron Waves in ICME Magnetic Clouds at 1 au

“…(see, e.g., Siu-Tapia et al 2015). The various in situ observations suggest the existence of Alfvén waves in ICME substructures, i.e., sheath and MC during CME-CME/CMEhigh-speed stream interactions (Raghav & Kule 2018a, 2018bRaghav et al 2018Raghav et al , 2019Shaikh et al 2019a;Dhamane et al 2023a;Raghav et al 2022Raghav et al , 2023Dhamane et al 2023b). However, how these waves dissipated in a flux rope structure remains an open question.…”