Keith Julien (1965–2024)

Keith Julien (June 12, 1965–April 14, 2024) was an applied mathematician who was widely regarded as the preeminent theoretical modeler of rotating convective turbulence, particularly as applied to planets and stars. His work spanned a wide range of fields, including asymptotic methods, advanced computation, geophysical and astrophysical fluid dynamics, and magnetohydrodynamics. Sociable, brilliant, and always humble, he was a sought-after collaborator and was skilled at coalescing groups, whether to develop new scientific frameworks, drink coffee, or play football (soccer). His pioneering work in multiscale asymptotics and computational physics led to numerous breakthroughs in our understanding of fluid dynamics across a broad range of natural settings. In this memoriam, we discuss Keith's life, the methods he developed, and the scientific and personal legacy he leaves behind.