What EUV Observations of Comet ISON Reveal About the Solar Corona

Recent advances in space-based solar observations have greatly progressed the study of sungrazing comets. They can now be imaged along the entirety of their perihelion passage, revealing details of their composition, structure, and size. Such comets are also unique probes of the solar corona. The debris deposited by sungrazers is rapidly ionized and subsequently forced to follow the ambient magnetic field. In this paper we present preliminary results from EUV observations of Comet ISON. We estimate the size of the comet nucleus based on the EUV radiance and compare with independent estimates. The variation of the EUV emission with wavelength provides limits on the density of the ambient corona, and the motion of ionized debris will be used to infer the coronal magnetic field structure.