Speaker
Description
Magnetic reconnection is a ubiquitous fundamental process in space and astrophysical plasmas that rapidly converts magnetic energy into some combination of flow energy, thermal energy, and non-thermal energetic particles. Over the past decade, a new experimental platform has been developed to study magnetic reconnection using strong coil currents powered by high power lasers at low plasma beta, typical conditions under which reconnection is energetically important in astrophysics [1]. KJ-class lasers were used to drive parallel currents to reconnect MG-level magnetic fields in a quasi-axisymmetric geometry, similar to the Magnetic Reconnection Experiment or MRX [2], and thus this platform is named micro-MRX. This presentation summarizes two major findings from micro-MRX: direct measurement of accelerated electrons [3] and observation of ion acoustic waves [4] during anti-parallel reconnection. The angular dependence of the measured electron energy spectrum and the resulting accelerated energies, supported by particle-in-cell simulations, indicate that direct acceleration by the out-of-plane reconnection electric field is at work. Furthermore, a sudden onset of ion acoustic bursts has been measured by collective Thomson scattering in the exhaust of magnetic reconnection, followed by electron acoustic bursts with electron heating and bulk acceleration. These results demonstrate that the micro-MRX platform offers a novel and unique approach to study magnetic reconnection in the laboratory beyond the capabilities provided by traditional magnetized plasma experiments such as MRX and the upcoming FLARE or (Facility for Laboratory Reconnection experiments) [5]. Implications of these laboratory findings to astrophysical scenarios and future work on studying other particle acceleration mechanisms and ion acoustic waves during magnetic reconnection are discussed.
[1] H. Ji, L. Gao, G. Pomraning, K. Sakai et al, “Study of magnetic reconnection at low-beta using laser powered capacitor coils,” submitted to Physis of Plasmas (2024)
[2] M. Yamada, H. Ji, S. Hsu, T. Carter et al., “Study of driven magnetic reconnection in a laboratory plasma,” Physis of Plasmas 4, 1936-1944 (1997)
[3] A. Chien, L. Gao, S. Zhang, H. Ji et al., “Non-thermal electron acceleration from magnetically driven reconnection in a laboratory plasma,” Nature Physis 19, 254-262 (2023)
[4] S. Zhang, A. Chien, L. Gao, H. Ji et al., “Ion and electron acoustic bursts during anti-parallel magnetic reconnection driven by lasers,” Nature Physis 19, 909-916 (2023)
[5] H. Ji, W. Daughton, J. Jara-Almonte, A. Le, A. Stanier, and J. Yoo, “Magnetic reconnection in the era of exascale computing and multiscale experiments,” Nature Reviews Physics 4, 263-282(2022)
