GEM: Phase Space Density Gradient of Energetic Electrons at Geosynchronous Orbit During Sharp Solar Wind Pressure Enhancements

GEM：太阳风压急剧增强期间地球同步轨道上高能电子的相空间密度梯度

• 批准号: 0902813
• 负责人: Xinlin Li
• 金额: $ 15.4万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-06-01 至 2012-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0902813&HistoricalAwards=false
• 关键词: GEM; Phase; Space; Density; Gradient

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).A major objective of the Geospace Environment Modeling (GEM) Focus Group on Space Radiation Climatology is to investigate the relationships between interplanetary conditions and trapped radiation belt particles and how these relationships change on long time scales (over a solar cycle) and apply this knowledge to the development of inner magnetospheric components of a Geospace General Circulation Model (GGCM). It is known that magnetic storms vary with solar wind conditions and that magnetospheric energetic particles have their largest variations during magnetic storms. However, the origin of radiation belt particles is still not fully understood and that has made it difficult to understand the physical mechanisms controlling the variability of these particles.The radial profile of the phase space density (PSD) of the radiation belt electrons for the first and second adiabatic invariants can provide insight of the source and the acceleration mechanisms. However, such a PSD radial profile is often difficult to obtain, mainly because of the lack of multipoint measurements and reliable magnetic field models with temporal scales on the order of 10 minutes, the drift period of a 1 MeV electron near geosynchronous orbit. This project is a two year research effort to determine the location of the energetic particle heating region by measuring the radial gradient of the PSD of energetic electrons and ions at and beyond geosynchronous orbit prior to and immediately after sharp solar wind pressure enhancements. From these measurements one can obtain the PSD at different radial distances prior to the solar wind pressure enhancements. Test-particle simulations will be performed to validate the PSD analysis and provide an estimate of the actual position of the particles before the arrival of the solar wind pressure enhancement. Sharp solar wind pressure enhancements, which can be due to interplanetary shocks and high speed solar wind streams, occur throughout the solar cycle. A statistical survey over a long term (approximately 1.5 solar cycles) will reveal any solar cycle and seasonal dependencies of the radial gradient.

该奖项是根据2009年美国复苏和再投资法案资助的地球空间环境建模空间辐射气候学重点小组的一个主要目标是调查行星际条件与被捕获的辐射带粒子之间的关系以及这些关系在长时间尺度上如何变化（在一个太阳周期内），并将这一知识应用于地球空间环流模式（GGCM）的磁层内部组成部分的开发。众所周知，磁暴随太阳风条件而变化，磁层高能粒子在磁暴期间变化最大。然而，辐射带粒子的起源至今还没有完全弄清楚，这使得控制这些粒子变化的物理机制难以理解，辐射带电子相空间密度（PSD）在第一和第二绝热不变量下的径向分布可以提供对源和加速机制的理解。然而，这样的PSD径向分布往往是难以获得的，主要是因为缺乏多点测量和可靠的磁场模型的时间尺度上的顺序为10分钟，漂移期的1兆电子地球同步轨道附近。该项目是一项为期两年的研究工作，目的是通过测量太阳风压力急剧增强之前和之后高能电子和离子在地球同步轨道内外的PSD径向梯度，确定高能粒子加热区的位置。从这些测量可以得到PSD在不同的径向距离之前的太阳风压增强。将进行测试粒子模拟，以验证功率谱密度分析，并提供太阳风压增强到达之前粒子实际位置的估计。太阳风压力的急剧增强，可能是由于行星际冲击和高速太阳风流，发生在整个太阳周期。一个长期的统计调查（大约1.5个太阳周期）将揭示任何太阳周期和季节的径向梯度的依赖关系。