GEM: The Time Sequence of Substorms in GEM Campaigns: A Comparison of Individual Events to Statistical Averages

磁层亚暴是从太阳风中提取能量并沉积在磁层、电离层和地球大气层中的过程的集合。 亚暴对近地环境有重大影响，并影响人类的许多系统。 这是对人类活动的一种自然危害，而且变得越来越重要。 不幸的是，亚暴的原因，特别是最具破坏性的阶段，膨胀阶段，是未知的。 近几年来，解释亚暴的最流行的物理模型是近地中性线（NENL）模型。 这个模型在组织近地等离子体片的大量观测方面取得了显著的成功，并成功地预测了磁尾等离子体团的存在和性质，磁尾等离子体团是地球在亚暴期间释放到太阳风中的等离子体和磁场的气泡。 一些新的观测结果没有被纳入NENL模型，似乎很难做到这一点。 亚暴的膨胀似乎是在接近同步轨道（6.6 Re）的当地午夜开始的，并向外传播到尾部。 这种膨胀开始于交叉尾电流片内边缘的闭合准偶极场线。 随后，它通过扰乱尾电流而向尾部移动，使尾电流沿着磁场线转向极光电离层。 一个新的模型，称为电流中断（CD）模型正在开发，以解释这些意见。 这个模型的某些版本预测了尾部等离子体片和磁场的动力学，这与NENL模型的预测完全相反，并且它所基于的观测结果。 这种幸运的情况应该很容易解决。 模型与观测结果要么一致，要么不一致，我们应该能够在两者之间做出决定。 建议重新检查近地等离子体片的观测结果，并将它们置于更坚实的基础上，以便有可能发展一个合理的亚暴扩展阶段的物理模型。 为此，加州大学洛杉矶分校的数据和其他研究人员的额外数据将用于研究与亚暴发生有关的现象的发生频率和时间延迟问题。 将使用亚暴开始的其他地面指标，包括卫星极光图像中的增亮、中纬度正海湾、Pi 2脉动爆发、同步磁场倾角的最大值以及同步轨道上的无色散等离子体注入。 待检查的特征包括磁场、粒子通量、等离子体压力、等离子体流量和温度的变化。 根据这些结果，将考虑不同的模型及其在解释观测结果方面的成功。

A magnetospheric substorms is the collection of processes by which energy is extracted from the solar wind and deposited in the magnetosphere, ionosphere and earth's atmosphere. Substorms have significant effects on the near-earth environment and affect many of man's systems. The represent a natural hazard to human activities that is becoming more important. Unfortunately, the cause of substorms, particularly of the most destructive phase, the expansion phase, is not known. For may years the most popular physical model explaining substorms has been the near-earth neutral line (NENL) model. This model has been remarkably successful in organizing numerous observations in the near-earth plasma sheet and successful predicted the existence and properties of the magnetotail plasmoid, a bubble of plasma and magnetic field that the earth releases to the solar wind during substorms. A number of new observations have not been incorporated in the NENL model, and it appears difficult to do so. It seems that the substorms expansion begins at local midnight very close to synchronous orbit (6.6 Re) and propagates outward into the tail. This expansion begins on closed, quasi-dipolar field lines at the inner edge of the cross-tail current sheet. Subsequently it moves tailward by disrupting the tail current, diverting it along magnetic field lines to the auroral ionosphere. A new model called the current disruption (CD) model is being developed to explain these observations. Some versions of this model predict dynamics of the tail plasma sheet and magnetic field that are diametrically opposite to the predictions of the NENL model, and the observations on which it is based. Such a fortunate circumstance should be easy to resolve. The model either agrees or disagrees with observations and we should be able to decide between them. It is proposed to re-examine the observations in the near-earth plasma sheet and place them on a firmer footing so that it will be pos sible to develop a reasonable physical model of the substorm expansion phase. To this end, data already at UCLA, and additional data from other investigators will be used to study the problems of frequency of occurrence and time delay of phenomena relative to substorms onset. Other ground indicators of substorm onset will be used including brightenings in satellite auroral images, midlatitude positive bays, Pi 2 pulsation bursts, maxima in inclination of synchronous magnetic field, and dispersionless plasma injection at synchronous orbit. Features to be examined include changes in magnetic field, particle fluxes, plasma pressure, plasma flow and temperature. Based on these results, the different models and their success in explaining the observations will be considered.