The Generation of Banded Chorus Waves in the Earth's Radiation Belt

无线电波在近地空间环境中自然产生。合唱波是一种与辐射带中的相对论粒子相互作用的无线电波。了解这些波和粒子之间的相互作用对于预测不断变化的空间环境及其社会影响非常重要。特别是，这使我们能够预测空间天气，并为国家商业和国防卫星和通信的影响做好准备-这是国家空间天气行动计划中规定的优先事项。该项目旨在通过分析来自货车艾伦探测器的数据和进行粒子模拟以帮助解释，探索地球辐射带带状合唱波的起源。自然发生的合唱波被认为在加速地球外辐射带的相对论电子，以及将~keV（和更高）的电子沉淀到高层大气中，引起扩散极光和脉动极光方面发挥着关键作用。合唱通常发生在两个不同的频带中，这两个频带由电子陀螺频率的一半处的间隙分开。这种双带结构的起源一直是一个长达半个世纪的公开科学问题。该项目通过系统地测量源区域的合唱波及其特性，将探索电子回旋频率一半处的谱隙是在磁赤道产生的，还是在波传播到高纬度时通过阻尼形成的。伴随带状合唱波的电子分布将进行统计研究和线性增长计算，以调查带状合唱波的直接能源。基于波浪和粒子分布的典型观测，将进行一维和二维粒子网格模拟，以探索可以解释带状合唱波的多阶段相互作用过程。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Radio waves are naturally produced in the near-Earth space environment. Chorus waves are a type of such radio waves that interact with relativistic particles in the radiation belts. Understanding the interactions between these waves and particles is important for predicting the changing space environment and its societal impacts. In particular, this allows us to predict space weather and prepare for impacts to national commercial and defense satellites and communications - a priority set out in the National Space Weather Action Plan. This project aims to explore the origin of banded chorus waves in Earth's radiation belt by analyzing data from the Van Allen Probes and performing particle-in-cell simulations to aid in interpretation. Naturally occurring chorus waves are believed to play a key role in accelerating relativistic electrons in the Earth's outer radiation belt, and in precipitating ~keV (and higher) electrons to the upper atmosphere, causing diffuse aurorae and pulsating aurorae. Chorus typically occurs in two distinct frequency bands separated by a gap at half of the electron gyro-frequency. The origin of this two-band structure has been a half-century-long open scientific question. This project, by systematically surveying the chorus waves and their properties right in the source region, will explore whether the spectral gap at half the electron gyro-frequency is generated at the magnetic equator, or is formed by damping as the waves propagate to higher latitudes. The electron distributions that accompany banded chorus waves will be statistically investigated and linear growth calculations made to investigate the direct energy source of banded chorus waves. Based on typical observations of waves and particle distribution, 1-Dimensional and 2-Dimensional particle-in-cell simulations will be performed to explore the multi-stage interaction processes that could account for the banded chorus waves.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.