RAPID: Neutron Monitors in the Twenty-First-Century

中子监测器是一种地面仪器，用于测量从太空撞击地球大气层的高能粒子的数量。 由于撞击地球的宇宙射线的强度并不均匀，因此在多个位置放置中子监测器以形成宇宙射线在太空中的完整图像非常重要。 中子监测器能够探测太阳高能粒子（SEP）以及由一直存在的银河宇宙射线（GCR）产生的背景中子。 他们产生了长达数十年的稳定可靠的宇宙射线强度测量记录。 此外，可以分析来自广泛分布的监测器网络的观测结果，以提供对最具能量和最强大的太阳粒子事件-地面增强（GLE）-的高时间分辨率测量。 特拉华州大学（UD）中子监测器在过去几年中一直缺乏外部资金，目前通过机构资金（来自UD和Bartol研究所）获得的支持最少。 然而，这笔资金将于2019年7月结束，并计划在2019年6月开始拆除这些车站，除非能够获得外部资金。 这个为期一年的RAPID项目的目的是恢复北美网络的功能条件和支持运行一年，直到可以获得更长期的支持。历史中子监测数据表明，在每个站的计数率随太阳活动周期而变化。 这是太阳调制银河宇宙射线的现象。 为了研究这种现象的起源，我们不能依赖于一个中子监测器的计数率：因此，我们需要导出宇宙射线强度作为粒子能量或粒子刚度的函数。 由于每一个中子监测器对高于一定地磁截止刚度的初级宇宙射线都很敏感，因此可以将不同纬度台站的测量结果联合收割机结合起来。 数十年测量的可靠性、稳定性和鲁棒性对于了解太阳的变化至关重要。 特别令人感兴趣的是，在过去两个太阳活动极小期的GCR强度是一个重要因素的观测所涵盖的时期内最大的。 如果没有中子监测器，这是不可能知道的。 目前的北美中子监测器网络与俄罗斯运营的台站相结合，其位置具有战略意义，可提供对宇宙射线角分布的精确、实时和三维测量。由于地球磁场和大气的综合影响，高纬度站点相对于低纬度站点具有上级方向灵敏度。 在UD的中子监测器所在的高纬度站点，SEP是焦点，而到达低纬度和中纬度站点的宇宙射线来自广泛分散的方向。 高纬度中子监测器的完整网络可以完整地了解SEP撞击地球的时间、地点和方向。除了空间天气预报外，中子监测器的数据，例如在为期一年的RAPID项目中收集的数据，也用于支持其他科学调查，而不仅仅是宇宙射线和日光层物理学的研究。 中子监测器数据的一个用途是监测宇宙射线产生的中子通量，用于广泛的实际应用，包括检测国土和国家安全的核威胁，计算机组人员和乘客的辐射剂量，了解单次事件的发生率。（软误差）在微电子设备，测量土壤和雪的水分含量，以及计算用于大气示踪剂和核条约核查的宇宙源放射性核素的产生率。 对于所有这些应用，中子和其他二次粒子产生的大气和表面材料的银河宇宙射线（偶尔由太阳粒子）的影响或一个重要的背景源。这个为期一年的RAPID项目将提供一个本科生的教育经验，以帮助维护和校准中子监测站在纽瓦克，特拉华州。 该RAPID项目的研究议程支持AGS部门在发现、学习、多样性和跨学科研究方面的战略目标。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

A neutron monitor is a ground-based instrument that measures the number of high-energy particles striking Earth's atmosphere from space. Because the intensity of cosmic rays hitting Earth is not uniform, it is important to place neutron monitors at multiple locations to form a complete picture of cosmic rays in space. Neutron monitors are capable of detecting Solar Energetic Particles (SEPs) as well as background neutrons produced by the ever-present Galactic Cosmic Rays (GCR). They produce decades-long records of stable and reliable cosmic ray intensity measurements. Furthermore, observations from wide-spread networks of monitors can be analyzed to provide high-time resolution measurements of the most energetic and powerful of solar particle events, Ground Level Enhancements (GLEs). The University of Delaware (UD) neutron monitors have suffered from lack of external funding over the past few years, and they are currently minimally supported through institutional funds (from the UD and the Bartol Research Institute). However, this funding will end in July of 2019, and plans are in place to dismantle the stations beginning of June, 2019, unless external funding can be secured. The purpose of this one-year RAPID project is to restore the North American network to a functional condition and support operation for one year until longer term support can be secured.The historic neutron monitor data have shown that at each station the count rate varies with the solar activity cycle. This is the phenomenon of solar modulation of galactic cosmic rays. To investigate the origin of the phenomenon, one cannot rely on the count rates of one neutron monitor: hence, one needs to derive the cosmic ray intensity as a function of particle energy or particle rigidity. Since each neutron monitor is sensitive to primary cosmic rays above some geomagnetic cutoff rigidity, one can combine measurements of stations at different latitudes. The reliability, stability and robustness of multi-decade measurements is critical for understanding the variability of the Sun. Of particular interest is the fact that the GCR intensity during the last two solar minimum is the greatest over the period covered by the observations by a significant factor. This would not have been known without neutron monitors. The current network of North American neutron monitors, combined with Russian operated stations are strategically located to provide precise, real-time, 3-dimensional measurements of the cosmic-ray angular distribution. Because of the combined effects of Earth's magnetic field and atmosphere, high latitude sites have superior directional sensitivity relative to low latitude sites. At the high latitude sites, where the UD's neutron monitors are located, the SEPs are in-focus, while cosmic rays arriving at low and mid latitude stations arrive from widely dispersed directions. The complete network of high latitude neutron monitors allows a complete picture of when, where, and from what direction SEPs strike Earth.In addition to space weather forecasting, data from neutron monitors, such as those to be collected during this one-year RAPID project, are also used in support of other science investigations, beyond studies of cosmic rays and heliospheric physics. One use of neutron monitor data is to monitor the flux of neutrons produced by cosmic rays for a broad range of practical applications, including detecting nuclear threats for homeland and national security, calculating the radiation dose to airplane crews and passengers, understanding the rate of single-event upsets (soft errors) in microelectronic devices, measuring soil and snow moisture content, and calculating the production rate of cosmogenic radionuclides used for atmospheric tracers and nuclear treaty verification. For all these applications, neutrons and other secondary particles produced in the atmosphere and surface materials by galactic cosmic rays (and occasionally by solar particles) are either the source of the effect or an important background.This one-year RAPID project will provide an educational experience for an undergraduate student to help maintain and calibrate the neutron monitor station in Newark, Delaware. The research agenda of this RAPID project supports the Strategic Goals of the AGS Division in discovery, learning, diversity, and interdisciplinary research.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.