Collaborative Research: GEM--Energetic Electron Nonlinear Interactions with Oblique Whistler-Mode Chorus Waves

哨声模式的“合唱”波是地球外辐射带中自然发生的无线电发射。这些波可以与捕获的高能电子（~10 keV至1 MeV）共振相互作用，既将它们加速到高速，又将它们散射到大气中作为“粒子沉淀”。“强烈的合唱波以与背景磁场成斜角的方式传播，在多个谐波中引起这种共振，并在几十秒内在快速的时间尺度上产生强烈的电子响应。然而，不同的共振谐波在塑造辐射带的全球状态中的作用仍然是未知的。这项研究将研究电子和这些强烈的斜合唱波之间的相互作用，以解决这个问题。了解这些过程的性质和机制对于预测空间天气及其对航天器表面和电子设备等敏感系统的影响十分重要。该项目还将支持早期职业科学家和一名研究生，研究结果将纳入公共宣传材料和德克萨斯大学达拉斯分校的本科课程。该项目的目标是解决三个具体的科学问题：1）在非线性波粒相互作用下，斜哨声模式合唱波的高能电子相空间密度如何演变？2)不同的电子谐波共振与磁层合唱波之间是否有可观察到的区别？如果有，区别是什么？3)在具有强烈斜向合唱波的事件中，朗道共振和回旋共振在塑造外辐射带中各自的作用是什么？为了回答这些问题，我们将开发斜合唱波包和电子相空间密度演化的数值模型，并定量地比较模型结果与美国宇航局的货车艾伦探测器的原位测量。重要的是，这项研究可能会导致发现电子非线性共振在独特的谐波，包括朗道共振的直接观测证据。这些重要的过程在理论上已经发生在外层空间，但还没有得到实验证据的证实。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估的支持。

Whistler-mode "chorus" waves are naturally occurring radio emissions in Earth's outer radiation belt. These waves can resonantly interact with trapped energetic electrons (~10 keV to 1 MeV), both accelerating them to high speeds and scattering them into the atmosphere as "particle precipitation." Intense chorus waves, propagating at oblique angles to the background magnetic field, invoke such resonances in multiple harmonics and produce strong electron responses on rapid timescales, within tens of seconds. However, the role of different resonance harmonics in shaping the global state of the radiation belt remains unknown. This investigation will study the interactions between electrons and these intense oblique chorus waves to address this problem. Understanding the properties and mechanisms of these processes is important for forecasting space weather and its effects on sensitive systems, such as spacecraft surfaces and electronics. This project will also support early-career scientists and a graduate student, and the findings will be incorporated into public outreach materials and undergraduate classes at the University of Texas at Dallas.The goal of this project is to address three specific scientific questions: 1) How does energetic electron phase space density evolve under nonlinear wave-particle interactions with oblique whistler-mode chorus waves? 2) Are there observable distinctions between different electron harmonic resonances with magnetospheric chorus waves and, if so, what are they? 3) What are the respective roles of Landau and cyclotron resonances in shaping the outer radiation belt in events with intense oblique chorus waves? To answer these questions, we will develop numerical models of both oblique chorus wave packets and electron phase space density evolution, and quantitatively compare model results with in-situ measurements made by NASA's Van Allen Probes. Importantly, this research may lead to the discovery of direct observational evidence of electron nonlinear resonances in distinctive harmonics, including Landau resonance. These important processes have been theorized to occur in outer space but have yet to be confirmed with experimental evidence.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.