Spatial and Temporal Dynamics of Important Types of Geomagnetic Disturbance

过去几年的研究首次证明，有几种根本不同类型的地磁扰动，其时间尺度从几分钟到几小时不等，地面磁场扰动从几十nT到~2000 nT不等。每一项都有独特的特点，反映了磁层内发生的明显不同的物理过程，并对影响空间和地面人造系统的总体空间气象活动作出了重大贡献。这里提出的研究的总目标是利用最近得到加强的极光电离层内电流、电场和光学发射的北极地面观测能力(Canopus、Norstar、SuperDARN)，结合适当的航天器观测(DMSP、POLE、IMAGE、LANL、GOES、GeoTail)，确定这些不同扰动的二维结构和时间动力学的重要方面。与以下扰动有关的具体目标包括：极向边界增强(极光指数：具有一个极光信号，可以从极光椭圆形的极光向南边界向赤道延伸，并与磁尾中的短时尺度流动爆发有关)：确定极光指数的二维结构，以及它们不同类型的二维结构发生的时间和地点。将局地二维结构与全球极光结构联系起来。通过确定是否在极光区域的超低频频率上通常显示出很大的功率，如果在极光椭圆形中看到的相同的超低频频率同时出现在夜侧等离子体层中，以及是否可以在与磁层相关的变化中看到一致的相速度，来调查黑洞指数是全球磁层振荡的一种表现形式的可能性。确定延伸到低纬度的束流是否如此之大，以至于它们同时影响从x~-30RE(或分界线附近)到同步轨道的黑夜等离子体片。确定PBI和极光电离层中等离子体流动之间的二维关系。动态压力扰动(太阳风动压增强引起极光椭圆形的大而迅速的增亮、加宽和向极地扩展)：确定(A)极冠上的重联和开放磁通量是否如最近的观测所表明的那样，总体上受到太阳风动态压力的强烈控制，(B)电离层和区域1电流的强度是否受到太阳风动压的强烈控制，对流驱动的晨边极光扰动(在午夜到黎明时分发生的极光增强，在对流增强的长时间内发生)：确定与这些黎明时分极光增强直接相关的电流(电离层和场排列)、电场和降水粒子特征。亚暴：找到一个关键问题的答案，即更接近50%或更接近100%的亚暴是由国际货币基金组织的变化触发的，这些变化导致大规模对流减少。这将使用最近增强的SuperDARN雷达网来确定极冠对流强度的减少(必须与基金组织的适当变化有关)是否与亚暴的开始直接相关，以及对于储存在尾部的一定数量的能量，亚暴扩展阶段的强度是否与对流强度的减少量成比例。

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.