Magnetospheric Mass Density Model

磁层质量密度模型

• 批准号: 0632740
• 负责人: Richard Denton
• 金额: --
• 依托单位: Dartmouth College
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-12-01 至 2011-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0632740&HistoricalAwards=false
• 关键词: Magnetospheric; Mass; Density; Model

Magnetospheric mass density controls the time response of the magnetosphere to external and internal forcing, and is thus important for understanding and predicting the effects of time dependent phenomena such as sudden impulses and Ultra-Low Frequency (ULF) waves. These dynamic processes can lead to acceleration or loss of radiation belt particles. In this project, spacecraft observations of toroidal Alfven waves will be used to evaluate the magnetospheric mass density and to develop a model to describe both the equatorial and field line distribution of the density as a function of parameters describing the state of the magnetosphere. The main spacecraft observations to be used are magnetic and electric field measurements by GOES, CRRES, Polar, and AMPTE/CCE spacecraft, and velocity moment measurements by LANL geosynchronous satellites. In addition to spacecraft observations of Alfven waves, in-situ electron density (CRRES and Polar), in-situ particle data (LANL geosynchronous satellites), and ground magnetometer data will be used to validate the model and evaluate the average ion mass. State of the art techniques for mass density inversion include adjustable magnetic field models and multi-harmonic frequency input to get the field line dependence of the mass density. Specific questions that will be considered as part of this project are: (1) What is the mass density in the magnetosphere, and how does it depend on L shell, the magnetic local time MLT, the state of the magnetosphere as specified by geomagnetic indices such as Dst, Kp, and the solar wind condition as specified by parameters such as the solar wind velocity and dynamic pressure, and how does the mass density vary during the solar cycle? (2) What is the distribution of mass density along magnetic field lines and what are the physical processes that determine this distribution? Under what conditions is there a peak in local density at the magnetic equator? (3) Is the mass density inferred from the toroidal Alfven waves consistent with the electron density? What is the contribution of heavy ions to the mass density, and how does this contribution depend on the state of the magnetosphere? What physical processes cause the accumulation of heavy ions at the magnetic equator? (4) Are toroidal Alfven frequencies measured on the ground consistent with those in space if the ground location is mapped to the spacecraft location?

磁层质量密度控制着磁层对外部和内部强迫的时间响应，因此对于理解和预测突发脉冲和超低频（ULF）波等随时间变化的现象的影响非常重要。这些动态过程可导致辐射带粒子的加速或损失。在该项目中，航天器对环形阿尔芬波的观测将用于评估磁层质量密度，并开发一个模型，以描述密度的赤道分布和场线分布，作为描述磁层状态的参数的函数。使用的主要航天器观测数据是GOES、CRRES、Polar和AMPTE/CCE航天器的磁场和电场测量数据，以及LANL地球同步卫星的速度矩测量数据。除了阿尔芬波的航天器观测外，原位电子密度（CRRES和Polar），原位粒子数据（LANL地球同步卫星）和地面磁力计数据将用于验证模型并评估平均离子质量。质量密度反演的现有技术包括可调磁场模型和多谐波频率输入，以获得质量密度的场线依赖性。作为该项目一部分将考虑的具体问题有：（1）磁层中的质量密度是什么，它如何取决于L壳层、磁地方时MLT、由地磁指数如Dst、Kp所确定的磁层状态以及由太阳风速度和动压等参数所确定的太阳风条件，在太阳活动周期中，质量密度是如何变化的？(2)质量密度沿沿着磁力线的分布是什么？决定这种分布的物理过程是什么？在什么情况下磁赤道上的局部密度会有一个峰值？(3)从环形阿尔芬波推导出的质量密度是否与电子密度一致？重离子对质量密度的贡献是什么，这种贡献如何取决于磁层的状态？什么物理过程导致重离子在磁赤道的积累？(4)如果将地面位置映射到航天器位置，在地面上测量的环形阿尔芬频率是否与空间中的一致？