• ISSN 2097-1893
  • CN 10-1855/P
马新,顾旭东,朱琪,焦鹿怀,王敬之,倪彬彬. 2023. 热等离子体影响嘶声波的色散特性和电子散射效应研究. 地球与行星物理论评(中英文),54(5):558-571. doi: 10.19975/j.dqyxx.2022-045
引用本文: 马新,顾旭东,朱琪,焦鹿怀,王敬之,倪彬彬. 2023. 热等离子体影响嘶声波的色散特性和电子散射效应研究. 地球与行星物理论评(中英文),54(5):558-571. doi: 10.19975/j.dqyxx.2022-045
Ma X, Gu X D, Zhu Q, Jiao L H, Wang J Z, Ni B B. 2023. Hot plasma effects on the dispersion properties of plasmaspheric hiss and its electron diffusion. Reviews of Geophysics and Planetary Physics, 54(5): 558-571 (in Chinese). doi: 10.19975/j.dqyxx.2022-045
Citation: Ma X, Gu X D, Zhu Q, Jiao L H, Wang J Z, Ni B B. 2023. Hot plasma effects on the dispersion properties of plasmaspheric hiss and its electron diffusion. Reviews of Geophysics and Planetary Physics, 54(5): 558-571 (in Chinese). doi: 10.19975/j.dqyxx.2022-045

热等离子体影响嘶声波的色散特性和电子散射效应研究

Hot plasma effects on the dispersion properties of plasmaspheric hiss and its electron diffusion

  • 摘要: 由等离子体层嘶声波引起的电子散射效应是地球内磁层电子损失的重要机制,也是地球内外辐射带间槽区形成的主要原因. 在量化嘶声波对高能电子散射效应的研究过程中,冷等离子体近似下的嘶声波色散关系被广泛应用. 然而在实际磁层等离子体环境中,热等离子体成分的存在会修正嘶声波的色散特性,进而也会影响嘶声波对高能电子的散射效应. 本文主要介绍了热等离子体影响嘶声波色散特性及其对电子散射效应的相关研究. 基于卫星波动观测数据的统计分析结果证实了热等离子体效应对嘶声波色散特性的修正作用;通过典型事例分析以及基于准线性理论的数值计算,分析了嘶声波散射高能电子对地磁活动条件和热等离子体参数(电子温度各向异性、热电子温度以及热电子占比)的依赖性. 结果表明,冷等离子体假设会高估100 keV以下能量电子以及较大投掷角范围内100 keV以上能量电子的散射系数,而低估较低投掷角范围内100 keV以上能量电子的散射系数. 此外,冷等离子体假设下共振区间会扩展到更低能量的电子,而基于观测的色散曲线结果则使100 keV以上电子与嘶声波的共振范围扩展到更小的投掷角区间. 随着热等离子体参数的增大,冷等离子体近似与热等离子体环境下的散射系数差异也逐渐增大. 相关研究结果对于模拟实际等离子体环境中嘶声波对电子的散射过程以及辐射带的动态演化具有重要意义.

     

    Abstract: Electron diffusion caused by plasmaspheric hiss is an important mechanism for the loss of electrons in Earth's inner magnetosphere; it has also been considered responsible for the formation of the slot region between inner and outer radiation belts. The cold plasma dispersion relation of plasmaspheric hiss is widely used to quantify the scattering effect of energetic electrons. However, the existence of hot plasma in a realistic magnetospheric plasma environment modifies the dispersion relation of plasmaspheric hiss, thereby affecting wave-induced energetic electron scattering. This paper presents the results of some recent studies on the influence of hot plasma on the dispersion relation and electron scattering effects of plasmaspheric hiss. Using statistical analysis results based on satellite wave observations, the modification of the hiss dispersion relation under the effects of hot plasma was verified. Furthermore, based on typical case analyses and numerical calculations using the quasi-linear diffusion theory, we investigated the dependence of the hiss-driven electron scattering rates on the geomagnetic activities and hot plasma parameters (i.e., temperature anisotropy, hot electron temperature, and hot electron abundance). The results revealed that the cold plasma dispersion relation overestimates the scattering rate of energetic electrons below 100 keV. For electrons above 100 keV, the differences between the cold plasma and hot plasma dispersion relations in terms of the induced scattering rates are somewhat smaller; this indicates that using the cold plasma dispersion relation can lead to the underestimation of the hiss-driven rates of electron pitch angle diffusion at smaller pitch angles and the overestimation of the rates at higher pitch angles. In addition, the cold plasma assumption can cause resonant diffusion down to lower electron energies; however, when the observed hiss wave dispersion curves are used, the resonant electron diffusion tends to extend to smaller pitch angles with a broader range. Notably, the differences in the scattering rates between the cold plasma and hot plasma dispersion relations increase with the hot plasma parameters. Therefore, our results are important for future simulations of the hiss wave-induced electron diffusion processes in the actual magnetospheric plasma environment and the dynamic variability of radiation belt electrons.

     

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