Broadband Electron Acceleration: Outstanding Physics Questions

宽带电子加速：突出的物理问题

• 批准号: 0741344
• 负责人: Patrick Newell
• 金额: $ 30万
• 依托单位: Johns Hopkins University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-03-15 至 2012-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0741344&HistoricalAwards=false
• 关键词: Broadband; Electron; Acceleration; Outstanding; Physics

This project is motivated by the recent realization that, after nearly three decades of research supporting the idea that auroral particle precipitation is dominated by processes that accelerate electrons and these electrons peak at a single energy, this theory may require revision. Broadband electron acceleration, which is believed to be associated with dispersive Alfven waves, is now recognized to be of roughly comparable significance, at least at some times. To investigate this idea, the largest data set of auroral precipitation, obtained by the DMSP satellite, will be explored. Identification algorithms and pattern recognition technique will be developed and employed to conduct a broad statistical study of the relative occurrences of broadband versus monoenergetic acceleration. Diffuse electron and diffuse ion precipitation will also be included in the study. Several issues with important physical consequences involving the relationship between broadband and monoenergetic acceleration will be addressed. These include: (1) a determination of whether broadband acceleration is affected by UV insolation, as is true for monoenergetic aurora; (2) what are the acceleration energies and energy fluxes associated with broadband acceleration? The numbers have been estimated to be tens of keV and several ergs per square centimeter per second, respectively; (3) do polar cap arcs contain broadband acceleration? (4) does broadband acceleration occur at lower latitudes, or is it as rare as anecdotal reports suggest. These specific topics are chosen to provide the clearest physical insights into comparing the acceleration mechanisms. For example, broadband acceleration occurs mainly in the poleward portion of the oval. This may occur because of a relationship to highly stretched magnetic field lines, or because of processes particular to the poleward edge of the oval (such as the boundary layer). The answers provided by this study will aid theorists in constructing unified models of auroral acceleration and in deciding when which process is likely to be active. This work will also help establish the relative proportions of diffuse electron, diffuse ion, monoenergetic accelerated electron, and broadband accelerated electron precipitation. The broader impacts of the project include the continuing development and maintenance of an extensive auroral particle database based on the observations from the DMSP satellite. The database, at http://sd-www.jhuapl.edu/Aurora, is freely available via the web and includes a variety of data products, from raw data to spectrograms to various high-level data abstractions. The database was begun under an earlier grant and has been used extensively by the space science community, including graduate students and postdoctoral fellows, but also provides information and articles geared to the general public.

该项目的动机是最近认识到，经过近三十年的研究支持极光粒子沉淀是由加速电子的过程主导的，这些电子在单一能量处达到峰值，这一理论可能需要修订。 宽带电子加速，这被认为是与色散阿尔芬波，现在被认为是大致相当的意义，至少在某些时候。 为了研究这一设想，将探索DMSP卫星获得的最大的极光降水数据集。 识别算法和模式识别技术将被开发和使用，以进行宽带与单能加速度的相对发生率的广泛的统计研究。 扩散电子和扩散离子沉淀也将包括在研究中。 几个重要的物理后果，涉及宽带和单能加速之间的关系的问题将得到解决。 其中包括：（1）确定宽带加速是否受到紫外线照射的影响，就像单能极光一样;（2）与宽带加速相关的加速能量和能量通量是什么？ 数字已被估计为几十千电子伏和几尔格每平方厘米每秒，分别;（3）做极冠弧包含宽带加速度？ (4)宽带加速发生在低纬度地区，还是像传闻中所说的那样罕见。 选择这些特定的主题是为了提供最清晰的物理见解来比较加速机制。 例如，宽带加速主要发生在椭圆的极向部分。 这可能是因为与高度拉伸的磁场线的关系，或者是因为椭圆的向极边缘（例如边界层）特有的过程。 这项研究提供的答案将有助于理论家建立极光加速的统一模型，并决定什么时候可能是活跃的过程。 这项工作还将有助于建立扩散电子、扩散离子、单能加速电子和宽带加速电子沉淀的相对比例。 该项目更广泛的影响包括继续开发和维护一个以DMSP卫星观测为基础的广泛的极光粒子数据库。 该数据库的网址是http：//sd-www.jhuapl.edu/Aurora，可通过网络免费查阅，其中包括各种数据产品，从原始数据到频谱图，再到各种高级数据摘要。 该数据库是在早些时候的一笔赠款下启动的，已被空间科学界广泛使用，包括研究生和博士后研究员，但也提供面向公众的信息和文章。