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The Maclaurin spheroid in disguise. New figures of equilibrium with external magnetic support

2024/06/27 by J.-M. Huré, Huré, Jean-Marc, Clément Staelen +1
Arts and Humanities · #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Medieval European Literature and History

paper · pdf · doi:10.48550/arxiv.2406.19210

openalex publication_date 2024/06/27 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

We show that a rigidly rotating, homogeneous ellipsoid of revolution threaded by a uniform, coaxial magnetic field is a possible figure of equilibrium. While the spheroidal shape is fully preserved, the rotation rate is modified. Accordingly, we extend the fundamental formula by Maclaurin. In contrast with the non-magnetic case, prolate shapes are permitted, but there are critical states in the form of maximum elongations, depending on ionisation fraction, ion/electron drift, magnetic field and mass-density. As checked from numerical simulations based on the Self-Consistent-Field method, prolate states survive to gas compressibility. The relevance to interstellar clouds is outlined.

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