McComas, D. J.Sharma, T.Christian, E. R.Cohen, C. M. S.Desai, M. I.Hill, M. E.Khoo, L. Y.Matthaeus, W. H.Mitchell, D. G.Pecora, F.Rankin, J. S.Schwadron, N. A.Szalay, J. R.Shen, M. M.Braga, C. R.Mostafavi, P. S.Bale, S. D.2023-04-062023-04-062023-01-27McComas, D. J., T. Sharma, E. R. Christian, C. M. S. Cohen, M. I. Desai, M. E. Hill, L. Y. Khoo, et al. “Parker Solar Probe Encounters the Leg of a Coronal Mass Ejection at 14 Solar Radii.” The Astrophysical Journal 943, no. 2 (January 27, 2023): 71. https://doi.org/10.3847/1538-4357/acab5e.1538-4357https://udspace.udel.edu/handle/19716/32631This article was originally published in Astrophysical Journal. The version of record is available at: https://doi.org/10.3847/1538-4357/acab5eWe use Parker Solar Probe (PSP) observations to report the first direct measurements of the particle and field environments while crossing the leg of a coronal mass ejection (CME) very close to the Sun (∼14 Rs). An analysis that combines imaging from 1 au and PSP with a CME model, predicts an encounter time and duration that correspond to an unusual, complete dropout in low-energy solar energetic ions from H–Fe, observed by the Integrated Science Investigation of the Sun (IS⊙IS). The surrounding regions are populated with low-intensity protons and heavy ions from 10s to 100 keV, typical of some quiet times close in to the Sun. In contrast, the magnetic field and solar wind plasma show no similarly abrupt changes at the boundaries of the dropout. Together, the IS⊙IS energetic particle observations, combined with remote sensing of the CME and a dearth of other "typical" CME signatures, indicate that this CME leg is significantly different from the magnetic and plasma structure normally assumed for CMEs near the Sun and observed in interplanetary CMEs farther out in the solar wind. The dropout in low-energy energetic ions may be due to the cooling of suprathermal ions at the base of the CME leg flux tube, owing to the rapid outward expansion during the release of the CME.en-USsolar coronal mass ejectionsinterplanetary magnetic fieldsinterplanetary mediuminterplanetary particle accelerationsolar energetic particlessolar windsolar coronal heatingsolar magnetic flux emergenceArticle