Does the Alfv\'en wave disrupt the large-scale magnetic cloud structure?

TL;DR

This study investigates how Alfvén waves interact with magnetic clouds, revealing their potential to dissipate or disrupt the cloud structure through observational analysis of wave flow directions and associated plasma phenomena.

Contribution

First observational evidence of Alfvén waves within magnetic clouds and their possible role in cloud disruption or dissipation.

Findings

Inward Alfvén wave flow dominates in magnetic clouds.

Outward Alfvén wave flow dominates in trailing solar wind.

Reduced Walén slope suggests wave dissipation or reconnection.

Abstract

Alfv\'en waves are primal and pervasive in space plasmas and significantly contributes to microscale fluctuations in the solar wind and some heliospheric processes. Here, we demonstrate the first observable distinct feature of Alfv\'en wave while propagating from magnetic cloud to trailing solar wind. The Wal\'en test is used to confirm their presence in selected regions. The amplitude ratio of inward to outward Alfv\'en waves is employed to establish their flow direction. The dominant inward flow is observed in magnetic cloud whereas trailing solar wind shows the dominant outward flow of Alfv\'en waves. The observed reduction in Wal\'en slope and correlation coefficient within magnetic cloud suggest (i) the simultaneous presence of an inward & outward Alfv\'en waves and/or (ii) a possibility of magnetic reconnection and/or (iii) development of thermal anisotropy and/or (iv) dissipation of Alfv\'enic fluctuations. The study implies that either the Alfv\'en waves dissipate in the magnetic cloud or its presence can lead to disruption of the magnetic cloud structure.