Spatial and Temporal Dynamics of Important Types of Geomagnetic Disturbance

过去几年的研究首次证明，地磁扰动有几种根本不同的类型，其时间尺度从几分钟到几小时不等，地磁场扰动从几十nT到2000 nT不等。每一种都有独特的特征，反映了磁层内发生的明显不同的物理过程。并对影响太空和地面上的人造系统的整体空间天气活动做出重大贡献。本文提出的研究总体目标是利用最近增强的北极地面观测能力（CANOPUS、NORSTAR、superdam），结合适当的航天器观测（DMSP、POLAR、IMAGE、LANL、GOES、Geotail），确定这些不同扰动的二维结构和时间动态的重要方面。与以下干扰相关的具体目标包括：极向边界增强（pbi：具有极光特征，可以从极光椭圆的极向边界向赤道延伸，并与磁尾中的短时间尺度流动爆发有关）：确定pbi的二维结构，以及它们不同类型的二维结构发生的时间和地点。将局部二维结构与全局极光结构联系起来。研究ppi是全球磁层振荡的一种表现形式的可能性，方法是确定ppi在极光区极低频频率是否普遍表现出较大的功率，在极光椭圆中看到的相同极低频频率是否同时在夜侧等离子体片中看到，以及ppi相关变化是否可以看到一致的相位速度。确定延伸到低纬度的ppi是否具有如此大的尺度，以至于它们同时影响从x ~ -30 RE（或分离矩阵附近）到同步轨道的夜侧等离子体表。确定pbi与极光电离层等离子体流之间的二维关系。动压扰动（由太阳风动压增强引起的极光椭圆大而迅速的变亮、变宽和向极地扩展）：确定(a)重联和极帽上开放磁通量的数量是否像最近的观测所表明的那样，通常受到太阳风动压的强烈控制，(b)电离层和1区电流的强度是否受到太阳风动压的强烈控制，以及(c)对流电场和跨极帽电位下降如何依赖于动压。对流驱动的晨面极光扰动（午夜到黎明的极光增强，发生在长时间的对流增强期间）：确定与这些晨面极光增强直接相关的电流（电离层和场对齐）、电场和降水粒子特征。亚暴：对近50%或近100%的亚暴是由导致大规模对流减少的IMF变化引发的这一关键问题获得答案。这将使用最近增强的SuperDARN雷达网络来完成，以确定极帽对流强度的减弱（必须与适当的国际货币基金组织变化有关）是否与亚暴的发生直接相关，以及对于存储在尾部的给定能量，亚暴扩展阶段的强度是否与对流强度的减弱成正比。

0136139LyonsResearch over the past few years has demonstrated for the first time that there are several fundamentally different types of geomagnetic disturbances having time scales ranging from a few minutes to a few hours and ground magnetic field perturbations ranging from a few tens of nT to ~2000 nT. Each has unique characteristics, reflects distinctly different physical processes occurring within the magnetosphere, and contributes significantly to overall space weather activity that affects manmade systems in space and on the ground. The general objective of the research proposed here is to determine important aspects of the two- dimensional structure and temporal dynamics of these different disturbances by using the recently enhanced capabilities for Arctic ground-based observations (CANOPUS, NORSTAR, SuperDARN) of currents, electric fields, and optical emissions within the auroral ionosphere, in combination with appropriate spacecraft observations (DMSP, POLAR, IMAGE, LANL, GOES, Geotail). Specific objectives related to the following disturbances include:Poleward boundary intensifications (PBIs: have an auroral signature that can extent equatorward from the poleward boundary of the auroral oval and are associated with short- time scale flow bursts in the magnetotail): Determine the two-dimensional structure of PBIs, and when and where their different types of two-dimensional structure occur. Relate the local two-dimensional structure to global auroral structure. Investigate the possibility that PBIs are a manifestation of a global magnetospheric oscillation by determining whether PBIs generally show large power at auroral-zone ULF frequencies, if the same ULF frequencies seen in the auroral oval are simultaneously seen in the nightside plasma sheet, and if consistent phase speeds can be seen for PBI-related variations. Determine if PBIs extending to low latitudes are of such large scale that they simultaneously affect the nightside plasmasheet from x ~ -30 RE (or near the separatrix) to synchronous orbit. Determine the two-dimensional relation between PBIs and plasma flows in the auroral ionosphere.Dynamic pressure disturbances (large and rapid brightening, broadening, and poleward expansion of the auroral oval caused by enhancements in solar wind dynamic pressure): Determine (a) whether reconnection and the amount of open magnetic flux over the polar caps is in general strongly controlled by the dynamic pressure of the solar wind as recent observations suggest, (b) whether the strength of ionospheric and region 1 currents are strongly controlled by solar wind dynamic pressure, and (c) how convection electric fields and the cross-polar cap potential drop depend upon dynamic pressure.Convection-driven morningside auroral disturbances (auroral enhancements at midnight to dawn MLTs that occur during prolonged periods of enhance convection): Identify the current (ionospheric and field aligned), electric field, and precipitation particle characteristics directly associated with these dawnside auroral enhancements.Substorms: Obtain an answer to the critical question of whether closer to 50% or closer to 100% of substorms are triggered by IMF changes that lead to a reduction in large- scale convection. This will be accomplished using the recently enhanced SuperDARN radar network to determine whether reductions in the strength of polar-cap convection (which must be related to appropriate IMF changes) are directly associated with substorm onset, and whether, for a given amount of energy stored in the tail, the strength of a substorm expansion phase is proportional to the amount of reduction in the strength of convection.