Modeling Energetic Particle Acceleration and Transport in a Solar Wind Region with Contracting and Reconnecting Small-scale Flux Ropes at Earth Orbit
Modeling Energetic Particle Acceleration and Transport in a Solar Wind Region with Contracting and Reconnecting Small-scale Flux Ropes at Earth Orbit
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DOI：
10.3847/1538-4357/ab521f
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发表时间：
2019-12
期刊：
影响因子：
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通讯作者：
J. L. le Roux;G. Webb;O. Khabarova;L.-L. Zhao-L.;L. Adhikari
中科院分区：
文献类型：
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作者：
J. L. le Roux;G. Webb;O. Khabarova;L.-L. Zhao-L.;L. Adhikari
提出了通过收缩和重新连接太阳风中的小规模磁力绳（SMFR）来加速高能粒子的新分析稳态和时间相关解决方案。为此，从现有的基础聚焦传输方程导出了电报员型帕克传输方程。该解统一了输运方程中存在的所有 SMFR 加速机制，表明混合导数输运项中重联电场产生的 SMFR 加速受到二阶费米 SMFR 加速的约束，并且需要二阶费米 SMFR 加速的存在。我们探索了这些解决方案在地球轨道太阳风中大规模重新连接电流片附近的动态 SMFR 区域中重现高能质子通量增强和~50 keV 至 5 MeV 之间光谱演化的潜力。结果表明，二阶费米 SMFR 加速涉及 SMFR 压缩和不可压缩平行剪切流的方差，并证实，由于平均 SMFR 压缩（之前在数据拟合中成功使用），一阶 SMFR 费米加速在使用合理的 SMFR 参数时，都是重现观察到的通量放大因子的可行选择。然而，预测的 SMFR 区域加速光谱空间演化的实质性定量差异可能提供一种区分观测中的一阶和二阶费米 SMFR 加速的方法。结论是，在确定一阶和二阶 SMFR 加速机制的相对作用之前，需要对 SMFR 加速事件中的 SMFR 参数进行更详细的数据分析。
New analytical steady-state and time-dependent solutions for the acceleration of energetic particles by contracting and reconnecting small-scale flux ropes (SMFRs) in the solar wind are presented. For this purpose, a telegrapher-type Parker transport equation was derived from the existing underlying focused transport equation. The solutions unify all SMFR acceleration mechanisms present in the transport equation, showing that SMFR acceleration by the reconnection electric field in the mixed-derivative transport term is constrained by and requires the presence of second-order Fermi SMFR acceleration. We explore the potential of these solutions in reproducing energetic proton flux enhancements and spectral evolution between ∼50 keV and 5 MeV in dynamic SMFR regions near large-scale reconnecting current sheets in the solar wind at Earth orbit. It is shown that second-order Fermi SMFR acceleration involving the variance in SMFR compression and incompressible parallel shear flow and confirmed that first-order SMFR Fermi acceleration, due to mean SMFR compression (successfully used before in data fits), are both workable options in reproducing observed flux amplification factors when using reasonable SMFR parameters. However, the predicted substantial quantitative differences in the spatial evolution of the accelerated spectra through the SMFR region might provide a way to distinguish between first- and second-order Fermi SMFR acceleration in observations. It is concluded that more detailed data analysis of SMFR parameters in SMFR acceleration events is needed before the relative role of first- and second-order SMFR acceleration mechanisms can be determined.