Observations of Switchback Chains in a Twin-CME Event

Abstract

Magnetic switchbacks, the localized and abrupt reversals in the magnetic field direction, are prominent features in the solar wind. We present the results of a study of switchbacks and the solar energetic particle (SEP) events associated with a twin-CME scenario – described as sequential eruptions of two coronal mass ejections (CMEs) from the same active region occurring within a short time interval – observed by Parker Solar Probe during August 18 – 19, 2022. The two consecutive CMEs, originating from active region (AR) 13078, displayed overlapping trajectories, and the primary CME traversed the wake of the pre-CME within its predicted turbulence duration window, leading to the formation of a significant solar energetic particle (SEP) event. The interaction of these CMEs was further complicated by their embedding within a high-speed stream emanating from a nearby coronal hole which led to increased solar wind density, plasma temperature, and intensified magnetic field strength. The interaction between the twin-CME event and the high-speed stream results in a compression and subsequent process which forced magnetic reconnection. This reconnection produced a distinct chain of magnetic switchbacks downstream of the CME wake, characterized by sharp directional changes in the magnetic field, enhanced transverse ion current, and suprathermal alpha particle flux. The orientation of the magnetic field of the high-speed stream as it surrounded the twin-CME suggests that interchange reconnection facilitated the emergence of switchback structures in the turbulent CME sheath, aligning with predictions from the model by Zank et al. (2020). In addition to the supportive evidences of interchange reconnection as a plausible explanation for switchbacks, our findings are expected to provide deeper insights into CME evolution in high-speed stream environments and have implications for understanding turbulent plasma processes that contribute to solar wind structuring.