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arXiv · 2604.02704

Collimation of diamagnetic laser-driven plasma outflows by an ambient magnetic-pressure gradient

Yigeng Tian·Chung Hei Leung·Arijit Bose·Riddhi Bandyopadhyay·Michael A. Shay·William H. Matthaeus
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Abstract

We present magnetohydrodynamic simulations of laser driven plasma outflows propagating along an externally applied poloidal magnetic field, designed to mimic coronal open-field plasma jets. Using the FLASH code with non-ideal terms (resistivity, Biermann battery, and Nernst advection) included, we model a CH target driven by a 3$\omega$ (351 nm) beam delivering 5 kJ over 10 ns and a uniform background field $\text{B}_0$ = 0 to 50 T. Under these conditions, the expanding plume develops a central low-density diamagnetic cavity bounded by a high-magnetic-pressure shell. Magnetic flux is advected from the plume center to its edge, and azimuthal diamagnetic currents form that decrease fields inside the cavity and amplify fields outside, producing a radial magnetic-pressure gradient that exerts an inward $\text{J}\times \text{B}$ force and radially confines the flow. We show that the collimation strengthens with increasing applied magnetic field, as stronger fields reduce the plasma $\beta$ and correspondingly enhance the confining $\text{J}\times \text{B}$ force.

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Yigeng Tian, Chung Hei Leung, Arijit Bose, Riddhi Bandyopadhyay, Michael A. Shay, William H. Matthaeus. 2026-04-03. Collimation of diamagnetic laser-driven plasma outflows by an ambient magnetic-pressure gradient. https://arxiv.org/abs/2604.02704

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