Abstract

The Earth’s magnetosphere and the ambient interplanetary environment can create favorable conditions for the nonlinear process of energy release in the form of changes in the topology of the magnetic field and current systems, particle acceleration, wave generation, and sharp gradients in the parameters inherent to a substorm phenomenon. Initially, early studies substantiated the role of variations in the solar wind parameters as a key factor responsible for the onset of a magnetospheric substorm; however, this factor was later shown not to be decisive. Over several decades, continuously improving methods for designing measurement tools and analyzing data helped to identify the processes that accompany the substorm phenomenon and describe them both qualitatively and quantitatively. However, there is no consensus in understanding the scenario of substorm development stepwise. The purpose of the research is to determine the propagation and orientation features of transients (fronts) in the current sheet of the Earth’s magnetotail during a substorm. To do this, the magnetic field measurements obtained by the four spacecraft of the Cluster II mission for July 20, 2013, are analyzed. During this event, spacecraft were located on the night side of the Earth’s magnetosphere and recorded changes in the geomagnetic field during the magnetospheric substorm. We used the single-spacecraft method for finding the minimum variance of the magnetic field and multispacecraft timing analysis involving cross-correlation of time series. The first method allows finding the direction of the normal to the structure under study; the second method makes it possible to find the direction and absolute value of its propagation velocity. The results of the study show that, with the development of substorms, the fronts that move towards the Earth exhibit a decrease in the propagation velocity and a significant degree of curvature. The first effect (a decrease in the propagation velocity of the fronts) indicates a decrease in the energy reserve of the current sheet for the generation of such transients, and the second effect (a significant degree of curvature) indicates the azimuthal localization of the front.

中文翻译：

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磁层副风暴期间磁性结构的动力学

摘要

地球的磁层和周围的行星际环境可以为能量释放的非线性过程创造有利的条件，其形式为磁场和电流系统拓扑的变化，粒子加速度，波的产生以及电磁场固有参数的急剧梯度。亚暴现象。最初，早期研究证实了太阳风参数变化是引起磁层次暴雨的关键因素的作用。但是，后来证明该因素不是决定性的。在过去的几十年中，不断改进的用于设计测量工具和分析数据的方法有助于识别伴随亚暴现象的过程，并对其进行定性和定量描述。然而，逐步了解亚暴发展的情况尚无共识。该研究的目的是确定在亚暴期间地球磁尾电流表中瞬变（前沿）的传播和定向特征。为此，分析了2013年7月20日第II团飞行任务的四艘航天器获得的磁场测量值。在此事件中，航天器位于地球磁层的夜侧，并记录了磁层亚暴期间地磁场的变化。我们使用单航天器方法寻找磁场的最小方差，并使用涉及时间序列互相关的多航天器定时分析。第一种方法可以找到所研究结构的法线方向。第二种方法可以找到其传播速度的方向和绝对值。研究结果表明，随着亚暴的发展，朝向地球的锋面传播速度降低，并且曲率明显降低。第一个效应（锋面传播速度的降低）指示电流板的能量储备的降低，以产生此类瞬变，第二个效应（显着的曲率度）表明锋面的方位角定位。