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年的《美国恢复和再投资法》（公法111-5）资助的。地理之间环境建模的主要目标（GEM）焦点小组对空间辐射气候的焦点是为了调查行星际条件和陷阱辐射带颗粒之间的关系（GGCM）。众所周知，磁风暴随太阳风条件而变化，并且在磁性风暴中，磁层能量颗粒的变化最大。但是，辐射带颗粒的起源仍未完全了解，这使得很难理解控制这些颗粒变异性的物理机制。对于第一和第二绝热不变的辐射带电子的相位空间密度（PSD）的径向谱，可以提供源头的洞察力和加速机制。但是，这种PSD径向剖面通常很难获得，这主要是因为缺乏多点测量和可靠的磁场模型，其时间尺度为10分钟，这是地球同步轨道附近的1 MeV电子的漂移周期。该项目是为期两年的研究工作，旨在通过测量在急剧太阳风压增强急剧之后的地球同步轨道上的能量电子和离子PSD的径向梯度来确定能量颗粒加热区域的位置。从这些测量值中，可以在太阳风压增强之前以不同的径向距离获得PSD。将进行测试粒子模拟以验证PSD分析，并在太阳风压增强到达之前对颗粒的实际位置进行估计。在整个太阳周期中，急剧的太阳风压增强可能是由于行星际冲击和高速太阳风流引起的。长期（约1.5个太阳周期）的统计调查将揭示径向梯度的任何太阳周期和季节性依赖性。