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Abstract Understanding plasma dynamics and nonthermal particle acceleration in 3D magnetic reconnection has been a long-standing challenge. In this paper, we explore these problems by performing large-scale fully kinetic simulations of multi-X-line plasmoid reconnection with various parameters in both the weak- and strong-guide-field regimes. In each regime, we have identified its unique 3D dynamics that lead to field-line chaos and efficient acceleration, and we have achieved nonthermal acceleration of both electrons and protons into power-law spectra. The spectral indices agree well with a simple Fermi acceleration theory that includes guide-field dependence. In the low-guide-field regime, the flux rope kink instability governs the 3D dynamics for efficient acceleration. The weak dependence of the spectra on the ion-to-electron mass ratio andβ(≪1) implies that the particles are sufficiently magnetized for Fermi acceleration in our simulations. While both electrons and protons are injected at reconnection exhausts, protons are primarily injected by perpendicular electric fields through Fermi reflections and electrons are injected by a combination of perpendicular and parallel electric fields. The magnetic power spectra agree with in situ magnetotail observations, and the spectral index may reflect a reconnection-driven size distribution of plasmoids instead of the Goldreich–Sridhar vortex cascade. As the guide field becomes stronger, the oblique flux ropes of large sizes capture the main 3D dynamics for efficient acceleration. Intriguingly, the oblique flux ropes can also experience flux rope kink instability, to drive extra 3D dynamics. This work has broad implications for 3D reconnection dynamics and particle acceleration in heliophysics and astrophysics.
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This content will become publicly available on May 1, 2026
A new single flux rope experiment for studying the dynamics of a magnetized plasma jet
We present the overview of a new experimental apparatus that has been developed to create a single flux rope for studying magnetized plasma jet dynamics, with a focus on the roles of Magnetohydrodynamic instabilities in magnetic reconnection and ion heating. The plasma is generated using coplanar electrodes with a single gas nozzle to create a single flux rope, high-voltage capacitor banks, gas puff valves, and a background magnetic field coil. This setup enables controlled exploration of various plasma stability regimes by adjusting external parameters. A comprehensive suite of diagnostic tools—including a He–Ne interferometer, ion Doppler spectroscopy, and a magnetic field probe array—has been implemented to measure key plasma parameters such as density, temperature, and magnetic field. Initial findings indicate that the apparatus can create a single flux rope and sustain it as a stable jet, a kink-unstable jet, and pinched plasma. In particular, kink instability results in significant ion heating, suggesting that magnetic reconnection may be driven by kink instability. These findings provide valuable insights into plasma dynamics relevant to space physics and magnetized inertial fusion, where fluid instabilities and magnetic reconnection are frequently observed.
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- Award ID(s):
- 2308853
- PAR ID:
- 10592646
- Publisher / Repository:
- AIP Publishing LLC
- Date Published:
- Journal Name:
- Review of Scientific Instruments
- Volume:
- 96
- Issue:
- 5
- ISSN:
- 0034-6748
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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