Observations of a Disconnection Event and Other Large-Scale Disturbances in the Ion Tail of Comet C/2022 E3 (ZTF)

Abstract

We analyze five large-scale tail disturbances in comet C/2022 E3 (ZTF)'s ion tail using images from astrophotographers, tracking specific features within the tail to determine their speeds. We employ a heliosphere model to estimate when the comet crossed the heliospheric current sheet (HCS). One event displays a distinct ion tail gap, suggesting that this was a disconnection event likely caused by magnetic reconnection associated with an HCS crossing. The tracked feature within the detached tail section exhibited increased acceleration under the influence of the solar wind compared to the still-attached portion of the tail. The other observed disturbances appear consistent with partial magnetic field rotations, and associated changes in the viewing geometry of the cross-tail current sheet, with some events also potentially linked to an interplanetary coronal mass ejection. We discuss typical time scales required for cometary ion tails to reach ambient solar wind speeds. Our results confirm that measured speeds of specific features within the visible part of ion tails tend to be considerably slower than the ambient solar wind that flows past the comet. An analysis of ion tail orientation can also provide speed estimates; however, these tend to align with typical solar wind speeds external to the tail and differ from the observed speeds of material within the tail. We discuss these methods and propose that the orientation of the ion tail is primarily controlled by the ambient solar wind flow outside the draped ion tail structure and is mostly unaffected by conditions within the ion tail.