CEDAR: Atmosphere-Ionosphere Coupling as Revealed in Global Magnetic Field Perturbations

CEDAR：全球磁场扰动揭示的大气-电离层耦合

• 批准号: 1552027
• 负责人: Jeffrey Forbes
• 金额: $ 34.35万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-05-15 至 2020-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1552027&HistoricalAwards=false
• 关键词: CEDAR; Atmosphere; Ionosphere; Coupling; Revealed

The Coupling, Energetics, and Dynamics of Atmospheric Regions (CEDAR) program, a broad-based, community-guided, upper atmospheric research program, is aimed at understanding the behavior of atmospheric regions from the lower atmosphere upward through the ionized upper layers of the atmosphere. Of particular interest is the coupling of the lower atmosphere to the ionized layer near 100-150 km that is called the "dynamo region". Large-scale wave variations of winds and temperatures in the lower atmosphere that are called thermal tides are generated by the heating caused by the daily passage of the Sun overhead or by the absorption of solar radiation by water vapor or stratospheric ozone at tropical latitudes. Other large-scale waves called planetary waves (PW) may also be caused by weather activity within the lower atmosphere. These large-scale waves may have periodicities as long as 16 days and very large horizontal wavelengths (thousands of km). These waves will propagate to higher altitudes where the winds, ionized gas content, and Earth?s magnetic field interact to generate electric fields and currents. These, in turn, will induce magnetic field perturbations that may be measured by the global network of magnetometers (141 sites). The production of PW and tidal waves within the lower atmosphere is highly variable, and consequently, the winds and temperature profiles associated with these wave structures will exhibit significant variability from day-to-day that can be detected through the application of sophisticated analysis procedures to the global magnetometer data. Part of the research motivation for this approach is that the electric fields generated within the dynamo region will map upward into the ionosphere above 250 km and generate variability of electron density at high altitudes that need to be understood for successful space weather forecasting, which has been given national priority. The research supported by this award would determine the ionospheric variability using the magnetometer data to measure the meridional and zonal components of magnetic field variations relative to a steady state baseline. The origins of this variability can then be considered in regard to possible factors to identify causal relationships. The award represents a strong potential for exciting and transformative science because the global analysis of ground magnetometer data will provide new insights into atmosphere-ionosphere coupling by tides and PW in a way that cannot be achieved by any satellite-based series of observations that is limited by the nature of local time sampling of the ionospheric variability. The broader impact of this award is that a woman Egyptian graduate student would be supported in her PhD work in this award thus enhancing the cultural diversity of the aeronomy community.The science motivation for this award is summarized by the following list of physical processes that need to be fully understood to understand space weather variability: (1) The dynamo region (ca.100-150 km) of Earth?s atmosphere is where electric fields are mainly generated through the dynamo action of neutral winds during daytime; (2) These electric fields have profound influences on the variability of the whole ionosphere; (3) Dynamo region variability is thought to originate from solar flux influences on electrical conductivity, and from the variability imposed by tidal and PW neutral winds, and disturbance winds associated with geomagnetic activity; (4) This variability has never been observationally quantified globally in a systematic way; (5) Knowledge concerning the variability of the dynamo region provides insight into the sources of variability for the overlying ionosphere; and (6) A global array of ground magnetometers exists that can provide the above knowledge. Examination of the global magnetometer data through application of standard time-series analysis tools would seek to understand the cause-effect factors underlying the ionospheric variability with the focus being that a major fraction of this ionospheric variability is likely to be caused by the large-scale waves reaching into this region from below. These results would be compared with variations of the standard solar and magnetic field indices to search for evidence of causal relationships between the tides and PW excited in the lower atmosphere and whose influences extend into the 100-150 km dynamo region generate electric fields that then map along magnetic field lines into the F region ionosphere. The F-region plasma redistributions that they produce carry with them the spatial and temporal signatures of these tides and PW, and of the processes that produced or modified them at lower altitudes.

大气区域耦合、能量学和动力学（CEDAR）计划是一个基础广泛、社区指导的高层大气研究计划，旨在了解从低层大气向上通过电离层上层大气的大气区域行为。特别令人感兴趣的是低层大气与100-150公里附近被称为“发电机区域”的电离层的耦合。低层大气中的风和温度的大规模波动变化称为热潮汐，是由于太阳每天从头顶经过或热带纬度的水蒸气或平流层臭氧吸收太阳辐射而产生的热量。其他被称为行星波（PW）的大尺度波也可能是由低层大气中的天气活动引起的。这些大尺度波的周期可能长达16天，水平波长非常大（数千公里）。 这些波将传播到更高的高度，那里的风，电离气体的内容，和地球？磁场相互作用产生电场和电流。 这些反过来又会引起磁场扰动，全球磁力计网络（141个站点）可以测量到这种扰动。低层大气中PW和潮汐波的产生是高度可变的，因此，与这些波结构相关的风和温度分布将显示出日复一日的显著变化，可以通过对全球磁力计数据应用复杂的分析程序来检测。 这种方法的部分研究动机是，发电机区域内产生的电场将向上映射到250公里以上的电离层，并在高空产生电子密度的变化，需要了解这种变化，以便成功地进行空间气象预报，这已成为国家的优先事项。该奖项支持的研究将利用磁强计数据确定电离层的可变性，以测量相对于稳态基线的磁场变化的纬向和纬向分量。然后可以考虑这种变异性的起源，以确定因果关系的可能因素。该奖项代表了令人兴奋和变革性科学的强大潜力，因为对地面磁力计数据的全球分析将提供对潮汐和PW的大气-电离层耦合的新见解，而这种方式是任何基于卫星的系列观测所无法实现的，这些观测受到电离层可变性当地时间采样性质的限制。 该奖项的更广泛影响是，一名埃及女研究生将在该奖项的博士研究工作中得到支持，从而增强高层大气物理学界的文化多样性，该奖项的科学动机概括为以下一系列需要充分了解以了解空间气象变异性的物理过程：（1）地球发电机区域（约100 -150公里）？（2）这些电场对整个电离层的变率有着深刻的影响：（3）发电机区的变率被认为是由太阳通量对电导率的影响、潮汐风和PW中性风以及与地磁活动有关的扰动风引起的;（4）这种变异性从来没有在全球范围内系统地进行过观测量化;（5）关于发电机区域变异性的知识有助于深入了解上覆电离层变异性的来源;（6）现有的全球地面磁力计阵列可以提供上述知识。 通过应用标准的时间序列分析工具对全球磁力计数据进行检查，将力求了解电离层变异性背后的因果因素，重点是这种电离层变异性的主要部分可能是由从下方进入该区域的大规模波造成的。这些结果将与标准太阳和磁场指数的变化进行比较，以寻找潮汐和低层大气中激发的PW之间因果关系的证据，PW的影响延伸到100-150公里发电机区域，产生电场，然后沿着沿着磁场线映射到F区域电离层。它们产生的F区等离子体再分布携带着这些潮汐和PW的空间和时间特征，以及在较低海拔产生或修改它们的过程。