NSWP: Magnetotail State and Dynamics Under Strong Forcing

NSWP：强强迫下的磁尾状态和动力学

• 批准号: 0720422
• 负责人: Robert McPherron
• 金额: $ 24.29万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-06-01 至 2013-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0720422&HistoricalAwards=false
• 关键词: NSWP; Magnetotail; State; Dynamics; Under

This project will investigate the effects of strong solar wind driving on Earth's magnetosphere. Strong driving produces a variety of responses including isolated magnetic substorms, sawtooth injection events, and steady magnetospheric convection (SMC). These response modes are associated with magnetic storms which usually exhibit frequent substorms during the main phase, but sometimes have no substorms, or simple activations, or random substorms, or substorm sequences. It is likely that the particular response mode depends on the state of solar wind and/or the state of the magnetosphere. It is possible that sudden fluctuations in the solar wind trigger a transition from one mode to another.The primary objective of this project is to define the state of the solar wind and the magnetosphere during each response mode. The instantaneous state of a variable is represented by a dynamic cumulative probability distribution (cdf) calculated from ensemble arrays with events as rows centered at a significant fiducial time such as the start or end of a storm main phase, or the beginning of a specific response mode. A broad window is advanced across the array in epoch time and data from all events are used to calculate the time variations in the cdf relative to the reference time. The state of the solar wind or magnetosphere is defined by a collection of contour maps of the cdfs for different important variables. A secondary objective is to represent the coupling between the solar wind and common measures of magnetospheric activity using local linear filters. These filters are calculated with a novel technique that determines the linear impulse response function at the center of a broad time window advanced across the ensemble arrays. The filters are represented by maps of the response function as a function of epoch time, and time series such as filter area. Systematic changes in the response should be evident as changes in the size or shape of the prediction filter. The third objective is to determine the importance of solar wind triggers in initiating or ending specific response modes. Large lists of solar wind dynamic pressure pulses and interplanetary magnetic field (IMF) changes will be associated with lists of magnetospheric response changes such as substorm onset and sawtooth injection onsets. Results will be portrayed by joint and marginal probability distributions with variable time delay of trigger and time delay of onset relative to preceding southward turning of the IMF.This project will advance understanding of the physical processes responsible for changes in the magnetosphere's response to changes in the solar wind. The new results will increase the accuracy of space weather forecasts in terms of the type of response expected and quantitatively through the creation of time dependent prediction filters. The results will provide guidance to numerical modelers of solar wind coupling. This project will provide an opportunity to combine the experience and data resources of two major research groups at UCLA in America and the St. Petersburg State University in Russia. The U.S. group will use statistical analysis of long time series while the Russian group will perform detailed studies of specific events. AT UCLA this project will provide an opportunity for several young research scientists, graduate students, and undergraduates to be involved in space weather research. Additionally, the project will make the database that will be created available to the space physics research community. This will be done using the NASA funded Virtual Magnetospheric Observatory.

该项目将研究强烈的太阳风驱动对地球磁层的影响。强驱动产生各种响应，包括孤立的磁亚暴、锯齿形注入事件和稳定的磁层对流(SMC)。这些响应模式与磁暴相关，磁暴在主相期间通常表现为频繁的亚暴，但有时没有亚暴，或简单的激活，或随机的亚暴，或亚暴序列。具体的反应模式很可能取决于太阳风的状态和/或磁层的状态。太阳风的突然波动可能会触发从一种模式到另一种模式的转换。该项目的主要目标是确定每种响应模式期间太阳风和磁层的状态。变量的瞬时状态由动态累积概率分布(CDF)表示，所述动态累积概率分布(CDF)是从集合数组计算的，所述集合数组具有以重要基准时间为中心的行，例如风暴主阶段的开始或结束，或特定响应模式的开始。在历元时间中跨阵列推进一个宽窗口，并且使用来自所有事件的数据来计算CDF中相对于参考时间的时间变化。太阳风或磁层的状态是由不同重要变量的CDF等值线图的集合来定义的。第二个目标是利用当地的线性过滤器来表示太阳风和磁层活动的共同测量之间的耦合。这些滤波器是用一种新的技术来计算的，该技术确定在跨群阵列推进的宽时间窗的中心处的线性脉冲响应函数。这些滤波器由响应函数作为历元时间的函数以及诸如滤波面积的时间序列的映射来表示。响应中的系统变化应明显表现为预测过滤器的大小或形状的变化。第三个目标是确定太阳风触发在启动或结束特定响应模式方面的重要性。太阳风动态压力脉冲和行星际磁场(IMF)变化的大列表将与磁层响应变化列表相关联，例如亚暴开始和锯齿形注入开始。结果将由联合和边缘概率分布描述，其中具有可变的触发时间延迟和相对于IMF先前南转的开始时间延迟。该项目将促进对导致磁层对太阳风变化的响应的变化的物理过程的理解。新的成果将通过建立依赖时间的预报过滤器，在预期的反应类型和数量方面提高空间天气预报的准确性。研究结果将为太阳风耦合的数值模拟人员提供指导。该项目将提供一个机会，将美国加州大学洛杉矶分校和俄罗斯圣彼得堡州立大学两个主要研究小组的经验和数据资源结合起来。美国小组将使用长时间序列的统计分析，而俄罗斯小组将对具体事件进行详细研究。在加州大学洛杉矶分校，这个项目将为几位年轻的研究科学家、研究生和本科生提供参与空间气象研究的机会。此外，该项目将向空间物理研究界提供将创建的数据库。这将使用NASA资助的虚拟磁层天文台来完成。