The Closest View of a Fast Coronal Mass Ejection: How Faulty Assumptions near Perihelion Lead to Unrealistic Interpretations of PSP/WISPR Observations

TL;DR

This study presents the closest observation of a fast coronal mass ejection by PSP/WISPR, revealing the importance of accurate 3D modeling over faulty assumptions like plane-of-sky projections, and reports the CME's extreme speed during solar cycle 25.

Contribution

The paper demonstrates the first polar coordinate tracking of a CME near perihelion and highlights the inaccuracies of plane-of-sky assumptions, emphasizing the need for 3D modeling for precise CME speed estimation.

Findings

CME speed estimated at approximately 2500 km/s using Thomson surface impact distance.

Plane-of-sky approach overestimates CME speed by more than three times.

The CME is among the fastest during solar cycle 25, with a speed of about 2700 km/s.

Abstract

We report on the closest view of a coronal mass ejection observed by the Parker Solar Probe (PSP)/Wide-field Imager for {Parker} Solar PRobe (WISPR) instrument on September 05, 2022, when PSP was traversing from a distance of 15.3~to~13.5~R$_\odot$ from the Sun. The CME leading edge and an arc-shaped {\emph{concave-up} structure near the core} was tracked in WISPR~field of view using the polar coordinate system, for the first time. Using the impact distance on Thomson surface, we measured average speeds of CME leading edge and concave-up structure as $\approx$2500~$\pm$~270\,km\,s$^{-1}$ and $\approx$400~$\pm$~70\,km\,s$^{-1}$ with a deceleration of $\approx$20~m~s$^{-2}$ for the later. {The use of the plane-of-sky approach yielded an unrealistic speed of more than three times of this estimate.} We also used single viewpoint STEREO/COR-2A images to fit the Graduated Cylindrical Shell (GCS) model to the CME while incorporating the source region location from EUI of Solar Orbiter and estimated a 3D speed of $\approx$2700\,km\,s$^{-1}$. We conclude that this CME exhibits the highest speed during the ascending phase of solar cycle 25. This places it in the category of extreme speed CMEs, which account for only 0.15\% of all CMEs listed in the CDAW CME catalog.