The Role of Ultra Low Frequency (ULF) Field Fluctuations in Radial Transport in the Outer Radiation Belt Electrons

在磁暴期间，地球外辐射带中的相对论电子表现出复杂的行为。电子通量随着从几分钟到几天的时间尺度而变化许多数量级。尽管越来越多的现场观测和一些建议的理论，我们还没有了解的运输和运输机制负责带的动态行为。该项目的重点是高能电子的径向传输，这是电子损失以及低能电子加速到相对论能量的基本机制。径向输运需要违反第三绝热不变量。在超低频（ULF）频率范围内，电子漂移运动的绝热性可以在电子与电场和磁场涨落的波粒相互作用过程中被打破。结果，粒子获得或失去对应于其向内或向外运输的能量。因此，描述运输带，它是必不可少的，以确定和量化的ULF现象，可以表现出共振与漂移运动的高能电子。本研究将联合收割机结合不同种类的超低频现象，并研究它们对带中径向输送的相对影响。为了量化ULF波对电子输运的影响，第一步将是确定它们的发生特性。高能电子只能与具有低方位波数值的ULF波（10）表现出漂移共振。在内磁层中，这种波以场线共振（FLR）的形式被观察到，场线共振是唯一普遍存在的具有窄带频谱和主要环形极化的ULF特征。FLR可以根据单个航天器的测量来识别。将根据释放和辐射效应综合卫星航天器提供的电场和磁场数据，对FLR的时空分布进行量化。与FLR不同，全球ULF场不能使用单个航天器观测进行量化，因为它们不能解决观测到的扰动的空间结构。为此目的，观测必须辅以磁层内场的全球模型。将使用具有自洽感应电场的时间相关Tsyganenko 04磁场模型。模型的独立控制参数将被调整，以适应各种全球ULF现象。在能够共振散射的高能电子的ULF场被量化之后，它们对辐射带电子的影响将使用测试粒子建模来分析。分析理论和详细的数值模拟将被使用。运输理论的几个基本问题，没有讨论过以前的研究，将被考虑。(1)径向输运是否可以用扩散来描述，或者是否需要更详细的处理？在径向扩散的框架下，对应于各种超低频驱动器的扩散系数是多少？(2)如果粒子表现出随机运动，它的起源是什么？它是由系统中的强非线性（确定性混沌）或超低频波动的随机特性引起的？(3)不同的超低频驱动因素的相对作用是否随地磁活动而改变？(4)离赤道动力学在实际的时变场中扮演什么角色？

During geomagnetic storms relativistic electrons in Earth's outer radiation belt exhibit complex behavior. Electron fluxes vary by many orders of magnitude over time scales from minutes to days. In spite of a growing volume of in situ observations and a number of proposed theories, we do not yet understand the transport and energization mechanisms responsible the dynamic behavior of the belt. This project is focused on radial transport of energetic electrons, a fundamental mechanism both of electron losses as well as acceleration of lower energy electrons to relativistic energies. Radial transport requires violation of the third adiabatic invariant. The adiabaticity of electron drift motion can be broken in the process of wave-particle interactions of the electrons with electric and magnetic field fluctuations in the ULF (Ultra Low Frequency) frequency range. As a result, particles gain or lose energy corresponding to their inward or outward transport. Thus, to describe transport in the belt, it is essential to identify and quantify ULF phenomena which can exhibit resonance with the drift motion of energetic electrons. This study will combine different kinds of ULF phenomena and investigate their relative impact on radial transport in the belt. To quantify the impact of ULF waves on the electron transport, the first step will be to determine their occurrence characteristics. Energetic electrons can exhibit drift resonance only with ULF waves which have low values of the azimuthal wave numbers ( 10). In the inner magnetosphere such waves are observed in the form of field line resonances (FLR) which is the only ubiquitous ULF feature with narrow band frequency spectrum and predominantly toroidal polarization. FLRs can be identified based on a single spacecraft measurements. The spatio-temporal profile of FLRs will be quantified based on electric and magnetic field data from the combined release and radiation effects satellite (CRRES) spacecraft. Unlike FLRs, global ULF fields cannot be quantified using single spacecraft observations, since they do not resolve spatial structure of the observed disturbances. For this purpose observations have to be complemented by a global model of the inner magnetospheric field. A time-dependant Tsyganenko 04 magnetic field model with self-consistent inductive electric fields will be used. Independent control parameters of the model will be adjusted to fit the various global ULF phenomena. After the ULF fields capable of resonant scattering of energetic electrons are quantified, their impact on the radiation belt electrons will be analyzed with the use of a test particle modeling. Both analytical theory and detailed numerical simulations will be used. Several fundamental questions of transport theory, not discussed by previous studies, will be considered. (1) Can radial transport be described by diffusion or is a more detailed treatment required? In the framework of radial diffusion what are the diffusion coefficients corresponding to various ULF drivers? (2) If particles exhibit stochastic motion, what is its origin? Is it caused by strong nonlinearity in the system (deterministic chaos) or a random character of ULF fluctuations? (3) Do the relative roles of different ULF drivers change with geomagnetic activity? (4) What is the role of off-equatorial dynamics in realistic time varying fields?