Axial magnetic field generation in laser-ionized plasmas due to the angular momentum absorption

Chen-Kang Huang^1,2*, Tzu-Yao Huang¹, Wei Lin¹, Shih-Fan Yang¹, Jheng-Yu Lee¹, Wu-Cheng Jiang¹, Chaojie Zhang³, Chan Joshi³, Hsu-Hsin Chu¹, Jyhpyng Wang^1,2, Chih-Hao Pai¹

¹Department of Physics, National Central University, Taoyuan, Taiwan
²Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan
³Department of Electrical and Computer Engineering, University of California Los Angeles, Los Angeles, USA

* Presenter:Chen-Kang Huang, email:powercurt@gmail.com

Controllable generation of magnetic fields in plasmas has widespread applications, including particle acceleration and plasma confinement. Through the inverse Faraday effect, the axial magnetic field is generated by the interaction of plasma particles and laser beams carrying angular momentum [1-3]. Theoretical studies have predicted the creation of tesla-level magnetic fields through laser ionization and absorption of optical angular momentum [4,5]. However, the inhomogeneous drift motion of ionized electrons can lead to significant electron density modulations, such as spiral patterns, filamentation, and plasma kinetic instabilities [6,7], which disrupt this magnetic field generation process. In this study, we investigate the relationship between the spiral electron density structure and the generation of the axial magnetic field using computer simulations. Our results show that the self-generated magnetic field initially reflects the structure of the electron density pattern. However, within several hundred femtoseconds, it evolves into an axial form with a peak field strength of several tens of tesla, depending on the laser and gas parameters. An experiment is proposed to validate these simulation results.

References
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[6] C. Zhang et al., Sci. Adv. 9, eaax4545 (2019).
[7] C.-K. Huang et al., submitted (2024).

Keywords: Laser plasma, Optical angular momentum, Magnetic field generation, Particle-in-cell simulation