September 30, 2022

PIC Simulation of Double Plasma Resonance and Zebra Pattern of Solar Radio Bursts by Li et al.*

The most-accepted one is the model of double plasma resonance (DPR) which, as its name suggests, indicates simultaneous actions of 2 kinds of resonance instabilities, i.e., the cyclotron resonance and the upper-hybrid (UH) resonance. Previous studies on DPR are primarily based on direct analysis without thinking about the generation of getting away radiations due to the non-linear plasma emission procedure. The procedure starts from the excitation of numerous waves, consisting of the UH, Z, and whistler (W) modes, followed by the nonlinear wave– wave coupling process to release the fundamental (F) and harmonic (H) plasma emissions. Ni et al. (2020) suggested that the F emission is created by the coalescence of almost-counter-propagating Z and W modes, and the H emission is given by the coalescence of almost-counter-propagating electrostatic UH modes.
“UH” stands for upper hybrid mode, “W” for whistler mode, “Z” for Z mode, “H” for harmonic plasma emission, and “O-F” stands for O mode around the fundamental plasma frequency.

Zebra patterns (ZPs) represent a spectral great structure with almost-equidistant or equidistant stripes of enhanced intensity against a broadband emission background, regularly observed in the vibrant spectra of solar radio bursts such as type IVs. There exist numerous circumstances for ZPs. The most-accepted one is the model of double plasma resonance (DPR) which, as its name suggests, means synchronised actions of two kinds of resonance instabilities, i.e., the cyclotron resonance and the upper-hybrid (UH) resonance.
Previous studies on DPR are primarily based on linear analysis without thinking about the generation of escaping radiations due to the non-linear plasma emission procedure. In a current research study utilizing the fully kinetic electro-magnetic particle-in-cell (PIC) simulation, Ni et al. (2020) presented considerable plasma emissions at both the essential (F) and harmonic (H) branches, via the ECMI procedure in plasmas with $ omega _ pe/ Omega _ = 10$. The procedure begins from the excitation of different waves, including the UH, Z, and whistler (W) modes, followed by the nonlinear wave– wave coupling procedure to release the basic (F) and harmonic (H) plasma emissions. Ni et al. (2020) recommended that the F emission is produced by the coalescence of almost-counter-propagating Z and W modes, and the H emission is offered by the coalescence of almost-counter-propagating electrostatic UH modes.
$ varying within two adjacent gyro-harmonic bands (9.5– 11.5). This likewise enables us to even more take a look at the event of the above ECMI-plasma emission process through in-depth criterion research study.
According to the simulations (see Figures 1 and 2), the developments of the UH and Z modes are undoubtedly dominated by the DPR impact, as demonstrated by the variations of their development rates in addition to their intensities with $omega _ pe/ Omega _ $. It was even more discovered that the intensity of the H emission is stronger than that of the F emission by about 2 orders of magnitude. The intensity of the H emission likewise varies with $omega _ pe/ Omega _ ce $, quasi-periodically, while the F emission is too weak to be considerable. This indicates that the ZPs emerge from the H emission, instead of the F emission as assumed in many earlier studies. The peak-valley contrast of the total intensity of the H emission (pr ZPs) is about 4, constant with some observational reports (e.g., Tan et al. 2014). These results are crucial to the understanding of the origin of solar ZPs and additional diagnostic efforts using radio data with ZPs.
= 9.5– 11.5$, and (b)–( c) the $omega-k$ dispersion curves for different modes. “UH” stands for upper hybrid mode, “W” for whistler mode, “Z” for Z mode, “H” for harmonic plasma emission, and “O-F” stands for O mode around the essential plasma frequency.
(d) The fitted rapid development rate of UH, Z, and W modes. =9.5-19.5$.
Based on the recent paper: Li, C., Chen, Y., Ni, S., Tan, B., Ning, H., & & Zhang, Z., PIC Simulation of Double Plasma Resonance and Zebra Pattern of Solar Radio Bursts, The Astrophysical Journal Letters, 2021, 909, L5, DOI: https://doi.org/10.3847/2041-8213/abe708
Recommendations
Ni, S., Chen, Y., Li, C., et al. 2020, ApJL, 891, L25
Tan, B., Tan, C., Zhang, Y., et al. 2014, ApJ, 790, 151
Zheleznyakov, V. V., & & Zlotnik, E. Y. 1975, SoPh, 44, 461
* Full list of Authors: Chuanyang Li, Yao Chen, Sulan Ni, Baolin Tan, Hao Ning, and Zilong Zhang

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