Contribution of Alfvénic Waves on the Formation and Deflection of Switchbacks: Insights from Two Decades of WIND Spacecraft Data

Abstract

Switchbacks, characterized by large-angle deflections of the local interplanetary magnetic field relative to the background, are frequently observed throughout the heliosphere and play a crucial role in the solar wind dynamics. Recent studies have highlighted the importance of local generation mechanisms, such as expanding waves, turbulence, velocity shear, and footpoint motion, in the formation of switchbacks. Utilizing nearly two decades of data from the WIND spacecraft near 1 au, we conducted a detailed investigation into the differences between switchbacks and their surrounding environment, focusing on the influence of solar wind conditions on their occurrence rate and deflection degree. Our findings indicate that switchbacks are embedded within Alfvén waves, and their occurrence rate and maximum deflection degree are significantly enhanced during large-amplitude Alfvén waves. Specifically, the occurrence rate of switchbacks during these periods shows no significant correlation with solar wind velocity, suggesting that Alfvén wave activity is the primary driver of switchback formation. Our results further indicate that the evolution of switchbacks is closely related to the evolution of Alfvén waves, and that velocity shear and footpoint motion do not play an additional role in their evolution. These findings provide valuable insights into the dynamics of switchbacks and their relationship with solar wind conditions, contributing to a deeper understanding of the complex interactions within the heliosphere.