The Origin of Plasmaspheric Hiss

等离子体层嘶嘶声（英语：Plasmaspheric hiss）是一种不相干的、带限的发射，主要存在于地球周围的稠密等离子体区域，被称为等离子体层。Hiss以哨声模式的电磁等离子体波传播，并且能够与货车艾伦辐射带中的高能电子共振。嘶嘶声在控制辐射带的结构和动力学方面的重要性早已被确立，但嘶嘶声本身的起源在过去的40多年里一直是一个悬而未决的问题。该项目将开发一种新发现的机制，涉及合唱波，似乎能够自然地解释观察到的频带，不相干的性质，白天/黑夜的不对称性，以及对地磁活动的依赖。现有的数值射线追踪代码将用于计算波的传播，以及使用释放和辐射效应综合卫星（CRRES）测量的通量的朗道阻尼。通过适当地加权合唱波的功率分布，并使用射线跟踪跟踪合唱到嘶嘶声的演变，嘶嘶声强度，频带和波法线角的分布将被量化为与地球的距离，磁当地时间和纬度的函数。然后，将通过重新计算若干不同磁层条件下的射线数据库，分析地磁活动对嘶嘶声特征分布的影响。在研究的最后一年，该项目将确定从（a）全球闪电活动，（B）方位角传播的影响，（c）在等离子体层羽流传播的嘶嘶声的贡献。计算的嘶嘶声分布将与卫星测量的观测结果进行比较。这项研究将主要由一名年轻的研究科学家和一名博士后学者完成。了解辐射带的物理特性对于理解和预测空间天气非常重要。

Plasmaspheric hiss is an incoherent, band-limited emission found predominantly in the dense-plasma region surrounding the Earth, known as the plasmasphere. Hiss propagates as an electromagnetic plasma wave in the whistler mode, and is able to resonate with the high-energy electrons in the Van Allen radiation belts. The importance of hiss in controlling the structure and dynamics of the radiation belts has long been established, but the origin of hiss itself has been an open problem for over four decades. This project will develop a newly discovered mechanism involving chorus waves that appears to be able to naturally account for the observed frequency band, the incoherent nature, the day/night asymmetry, and the dependence on geomagnetic activity. An existing numerical ray tracing code will be used to calculate wave propagation, together with Landau damping using fluxes measured by the Combined Release and Radiation Effects Satellite (CRRES). By properly weighting the power distribution of chorus waves and tracking the evolution of chorus into hiss using ray tracing, the distribution of hiss intensity, frequency band, and wave normal angle will be quantified as a function of distance from the Earth, magnetic local time, and latitude. The effects of geomagnetic activity on the distribution of hiss characteristics will then be analyzed by recalculating the ray database under a number of different magnetospheric conditions. In the final year of the study, the project will determine contribution to hiss from (a) global lightning activity, (b) the effects of azimuthal propagation, and (c) propagation in plasmaspheric plumes. The computed hiss distributions will be compared with observations from satellite measurements. The research will be done primarily by a young research scientist and a postdoctoral scholar. Understanding the physics of the radiation belts is important to understanding and being able to forecast space weather.