GEM: Substorm Physics in the GEM Geospace General Circulation Model: Linking a Tail-Dynamics Module with the Rice Convection Model

GEM：GEM 地球空间大气环流模型中的亚暴物理：将尾部动力学模块与水稻对流模型联系起来

• 批准号: 9625607
• 负责人: Joachim Birn
• 金额: --
• 依托单位: Department of Energy Albuquerque Operations Office
• 依托单位国家: 美国
• 项目类别: Interagency Agreement
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-08-15 至 1999-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9625607&HistoricalAwards=false
• 关键词: GEM; Substorm; Physics; Geospace; General

This is a three-year research program to investigate the nature of a newly discovered ionospheric source for ion energization and transport. The topic of ion energization is one of paramount importance in magnetospheric physics because ions carry the bulk of the particle energy and thereby play a central role in the molding of that environment. The proposed program directly addresses one of the most puzzling problems of ion energization - that is, how are heavy (O+) ions accelerated at low altitudes in the ionosphere and transported upward in large numbers to the magnetosphere? This question is crucial because (1) the abundance of O+ ions found throughout the magnetosphere requires some means by which large fluxes of thermal ions are transported upward from the ionosphere, and (2) thermal-ions upflows (TIU) and transversely accelerated ions (TAI) have been observed at altitudes as low as 400 km in the ionosphere. Other observations have demonstrated the existence of at least one class of TIU events that is characterized by the absence of ion frictional heating and the presence of elevated electron temperature, features that cannot be easily explained by known mechansims. These findings indicate that the process responsible for the transport of large fluxes of terrestrial ions to the magnetosphere has not yet been identified. We have recently described a new, ion energization source Tsunoda and Kagan, 1995 that appears to be the missing mechanism. The new source consists of Lorentz-type forces that arise because of the presence of a perturbation magnetic field, for example, that associated with a large-scale field-aligned current system. This perturbation magnetic field acts together with a latituinal pressure gradient or current (directed orthogonal to one another and transverse to B ) to produce a Lorentz-type force in a direction parallel or antiparallel to B . As described by Tsunoda and Kagan 1995 , and in this proposal, this mechanism is capable o f accounting for the class of TIU events that occur without ion heating. More exciting however, is the likelihood that these field-aligned Lorentz forces can account for a number of related but stil puzzling observations including (1) TIUs produced by ion heating, (2) the transport of molecular ions into the magnetosphere, (3) the triggering of the ion-cyclotron and ion- acoustic instabilities, (4) the transverse acceleration of ions by electrostatic ion-cyclotron waves, (5) the development of ion- acoustic turbulence and anomalous resistivity, and (6) elevated electron temperatures in upward field-aligned current regions. Given the potential of field-aligned Lorentz forces for explaining a variety of ion-acceleration-related phenomena, an investigation of a larger database of incoherent scatter radar data will be undertaken of determine if the observations support the predictions of this novel theory.

这是一项为期三年的研究计划，旨在调查新发现的电离层离子迁移和传输源的性质。在磁层物理学中，离子轨道是最重要的课题之一，因为离子携带着粒子能量的大部分，因此在塑造磁层环境中起着核心作用。该计划直接解决了离子束中最令人困惑的问题之一，即重离子（O+）是如何在电离层的低空加速并大量向上传输到磁层的？这个问题是至关重要的，因为（1）在整个磁层中发现的O+离子的丰度需要一些方法，通过这些方法，大通量的热离子从电离层向上传输，以及（2）在电离层中低至400公里的高度上已经观察到热离子上升流（TIU）和横向加速离子（TAI）。其他观测已经证明存在至少一类TIU事件，其特征在于不存在离子摩擦加热和存在升高的电子温度，这些特征不能很容易地用已知的机制来解释。这些发现表明，负责传输的过程中的大通量的地球离子的磁层尚未确定。我们最近描述了一种新的离子源Tsunoda和Kagan，1995年，似乎是失踪的机制。这个新的源由洛伦兹型力组成，这种力是由于扰动磁场的存在而产生的，例如，与大尺度场向电流系统相关的扰动磁场。该扰动磁场与纬向压力梯度或电流（彼此正交并横向于B）一起作用，以在平行或反平行于B的方向上产生洛伦兹型力。如Tsunoda和Kagan 1995所述，在该提议中，该机制能够解释在没有离子加热的情况下发生的TIU事件的类别。然而，更令人兴奋的是，这些场向洛伦兹力可能解释了许多相关但仍然令人困惑的观测结果，包括（1）离子加热产生的TIU，（2）分子离子进入磁层的运输，（3）离子回旋和离子声不稳定性的触发，（4）静电离子回旋波对离子的横向加速，（5）离子声湍流和异常电阻率的发展;（6）向上场向电流区电子温度的升高。考虑到场向洛伦兹力解释各种离子加速相关现象的潜力，将对非相干散射雷达数据的更大数据库进行调查，以确定观测结果是否支持这一新理论的预测。