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

惠斯勒模式的“合唱”波是地球外辐射带中自然产生的无线电辐射。这些波可以与被俘获的高能电子(~10keV到1 MeV)发生共振相互作用，将它们加速到高速，并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传播，在多个谐波中激发这样的共振，并在快速的时间尺度上产生强烈的电子响应，在几十秒内。然而，不同的共振谐波在塑造辐射带全球状态方面的作用尚不清楚。这项研究将研究电子与这些强烈的斜和声波之间的相互作用，以解决这个问题。了解这些过程的性质和机制对于预报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。这个项目还将支持职业生涯早期的科学家和一名研究生，研究结果将被纳入德克萨斯大学达拉斯分校的公共宣传材料和本科生课程。该项目的目标是解决三个具体的科学问题：1)在带有倾斜哨声模式合唱波的非线性波-粒子相互作用下，高能电子相空间密度是如何演变的？2)不同的电子谐振波与磁层合声波之间是否有明显的区别，如果有，它们是什么？3)兰道共振和回旋加速器共振在形成具有强烈倾斜合唱波的事件中的外辐射带中分别扮演着什么角色？为了回答这些问题，我们将建立斜合唱波包和电子相空间密度演化的数值模型，并将模型结果与NASA的Van Allen探测器的现场测量结果进行定量比较。重要的是，这项研究可能导致发现电子在独特的谐波中存在非线性共振的直接观测证据，包括朗道共振。这些重要的过程已经被理论上认为发生在外层空间，但还没有得到实验证据的证实。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.