Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province, College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070, China
Abstract By one-dimensional particle-in-cell (PIC) simulations, the propagation and stability of relativistic electromagnetic (EM) solitary waves as well as modulational instability of plane EM waves are studied in uniform cold electron-ion plasmas. The investigation not only confirms the solitary wave motion characteristics and modulational instability theory, but more importantly, gives the following findings. For a simulation with the plasma density 1023 m-3 and the dimensionless vector potential amplitude 0.18, it is found that the EM solitary wave can stably propagate when the carrier wave frequency is smaller than 3.83 times of the plasma frequency. While for the carrier wave frequency larger than that, it can excite a very weak Langmuir oscillation, which is an order of magnitude smaller than the transverse electron momentum and may in turn modulate the EM solitary wave and cause the modulational instability, so that the solitary wave begins to deform after a long enough distance propagation. The stable propagation distance before an obvious observation of instability increases (decreases) with the increase of the carrier wave frequency (vector potential amplitude). The study on the plane EM wave shows that a modulational instability may occur and its wavenumber is approximately equal to the modulational wavenumber by Langmuir oscillation and is independent of the carrier wave frequency and the vector potential amplitude. This reveals the role of the Langmuir oscillation excitation in the inducement of modulational instability and also proves the modulational instability of EM solitary wave.
Fund: Project supported by the National Natural Science Foundation of China (Grant Nos. 11765017, 11865014, 11847304, and 11764039), the Scientific Research Project of Gansu Higher Education, China (Grant No. 2019B-034), and the Science and Technology Project of Guizhou Province, China (Grant No. Qiankehe-LH-[2017]7008).
Rong-An Tang(唐荣安), Tiao-Fang Liu(刘调芳), Xue-Ren Hong(洪学仁), Ji-Ming Gao(高吉明), Rui-Jin Cheng(程瑞锦), You-Lian Zheng(郑有莲), and Ju-Kui Xue(薛具奎) Propagation dynamics of relativistic electromagnetic solitary wave as well as modulational instability in plasmas 2021 Chin. Phys. B 30 015201
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