Determining the processes behind near-steady radiation belt losses

等离子体粒子（离子和电子）被困在地球磁层的闭合场线上，可以通过一系列波粒相互作用被激发到MeV的能量。这些粒子组成了货车艾伦辐射带--两个类似金牛座的高能粒子区域，从近似地球同步轨道向内环绕地球。辐射带中高能粒子的数量是加速到高能量的粒子（例如通过扩散或与哨声波的相互作用）与从该区域丢失的粒子（例如通过向外扩散、通过磁层顶丢失和丢失到大气中）之间的平衡。最近对辐射带中粒子数量的研究表明，在地磁活动低的时期，该区域粒子数量随时间的比例变化几乎是恒定的，因此辐射带不断泄漏粒子。了解这些损失过程对于了解支撑辐射带的物理学非常重要，这对于正确模拟辐射带和预测空间天气的影响至关重要，并且还可以提供有关降水进入高层大气的速率的信息，在高层大气中，高能带电粒子可以改变高空大气化学。学生将研究这种损失在哪里最占主导地位，以及这种损失与辐射带内某些初始条件的关系，现有的波粒相互作用理论是否可以解释这些损失率，以及这些损失率是否在辐射带增强时也保持不变。该项目将主要涉及使用美国航天局货车艾伦探测器的数据，不过其他数据来源包括LANL和GOES地球同步卫星、低地球轨道SAMPEX和POES航天器以及地面STP数据。

Plasma particles (ions and electrons) trapped on closed field-lines in Earth's magnetosphere can be energised to MeV energies by a range of wave-particle interactions. These particles make up the Van Allen Radiation Belts - two taurus-like regions of high energy particles encircling the Earth from approximately geosynchronous orbit inwards. The number of high energy particles in the radiation belts is a balance between particles being accelerated to high energies, e.g. by diffusion or interactions with whistler-mode waves, and particles being lost from the region, e.g. by outward diffusion, loss through the magnetopause and loss to the atmosphere. Recent studies of the number of particles in the radiation belts have shown that the proportional change in the number of particles in this region with time is almost constant during periods of low geomagnetic activity, and as such the radiation belts are constantly leaking particles. Understanding these loss processes is important in order to understand the physics that underpins the radiation belts, which is crucial in order to correctly model this and predict the impact of space weather, and also to provide information as to the rates of precipitation into the upper atmosphere, where energetic charged particles can alter high-altitude atmospheric chemistry.In this project, the student will examine where this loss is most dominant and how this relates to some initial conditions within the radiation belts, whether existing wave-particle interaction theory can explain these loss rates, and whether these loss rates also hold during times when the radiation belts are being enhanced. This project will primarily involve using data from the NASA Van Allen Probes, although further data sources include the LANL and GOES geosynchronous satellites, the low-Earth orbiting SAMPEX and POES spacecraft and ground-based STP data.