Ground Level Enhancement Event Monitor (GLEEM)

太空天气带来的风险正被越来越广泛地认识到，它们现在被列入了英国国家风险登记册。特别是，包含大量能量大于300 MeV的粒子的硬太阳高能粒子(SEP)事件构成了相当大的风险。地面中子监测器在地球表面探测到这样的太阳事件，称为地面增强(GLE)事件，自20世纪40年代以来一直这样做。通常每年大约有一次GLE事件，持续时间从1到12个小时，用仪器观测到的最大事件是1956年2月23日在利兹测量的。除其他地面可探测的空间气象现象外，GLE事件还有可能扰乱重要的国家基础设施，如电网、运输(航空和铁路)、卫星应用和通信以及安全关键的电子控制系统。根据地球表面中子监测器的测量结果推断地球大气层顶部的空间天气辐射，需要一个全球分布的监测器和模型网络，模拟地球大气层中粒子相互作用的物理过程。气象局负责向政府部门和民航等部门报告空间气象风险，并认识到它没有足够的能力为空间气象辐射危害提供必要的服务。例如，全球只有50个地面中子监测仪仍在运行，这些监测仪都不在英国。在过去的60年里，现有监测器及其仪器的设计几乎没有什么变化，它们依赖于剧毒的探测器材料(三氟化硼)或现在过于昂贵的探测器材料(氦-3)，而且它们都是包含铅屏蔽的大而笨重的仪器。对这些材料在其他涉及中子探测的应用中的使用的关注导致了大量替代探测技术的发展。尽管现有的替代中子探测器范围很广，但很少有适合地面中子监测的具体应用要求，因为地面中子监测需要高探测效率和几十年的稳定性。GLEEM将采用为存在类似挑战的无人值守保障监测仪开发的探测器技术，以开发和展示适用于相对偏远地点的无人值守操作的新型紧凑型仪器的原型网络。新的监测仪将在现有的监测点进行测试，以验证这种仪器能够产生与现有地面中子监测仪相当的结果，并有可能增强现有的全球能力。作为概念验证，将演示一个由两台仪器组成的网络，作为测试部署的一部分，以提供兼容的数据流，以便纳入英国气象局空间气象业务中心(MOSWOC)，并提供给作为SWIMMR N2项目的一部分而开发的航空辐射模型，SWIMMR N2是由NERC资助的SWIMMR航空风险模型(SWWARM)项目的一部分。最终，GLEEM的目标是建造和操作一种明显更便宜的仪器，在英国重新引入监测，并促进全球空间天气监测的大幅增加。

The risks posed by space weather are becoming more widely recognised, and they are now listed on the UK National Risk Register. In particular, hard solar energetic particle (SEP) events containing a substantial flux of particles with energies greater than 300 MeV pose a considerable risk. Ground level neutron monitors detect such solar events, termed ground level enhancement (GLE) events, at the Earth's surface and have done so since the 1940s. Typically there is around one GLE event per year and they have durations from 1 to 12 hours, the largest event observed with instruments was measured in Leeds on 23 February 1956. Besides other ground-detectable space weather phenomena, GLE events have the potential to disrupt critical national infrastructures, such as the power grid, transport (aviation and rail), satellite applications and communications, and safety critical electronic control systems. Deducing space weather radiation at the top of the Earth's atmosphere from measurements made by neutron monitors on the Earth's surface requires a globally distributed network of monitors and models that simulate the physics of particle interactions in the Earth's atmosphere. The Met Office is responsible for reporting space weather risks to government departments and civil aviation, among others, and has recognised that it does not have sufficient capabilities to provide the necessary services for space weather radiation hazards. For example there are only 50 ground level neutron monitors worldwide still operational, none of these are located in the UK. The design of existing monitors and their instrumentation have changed very little over the last sixty years, they rely on detector materials that are either highly toxic (boron trifluoride) or now too expensive (helium-3), and are large and bulky instruments containing lead shielding.Concerns over the use of these materials in other applications involving neutron detection has led to the development of a plethora of alternative detection technologies. Despite the wide range of alternative neutron detectors now available, very few are suitable for the specific application requirements of ground-level neutron monitoring, where high detection efficiency and several decades of stability are essential. GLEEM will adopt detector technology that was developed for unattended safeguards monitors, where similar challenges exist, to develop and demonstrate a prototype network of new, compact instruments, that are suited for unattended operation in relatively remote locations. The new monitors will be tested at existing monitoring sites to verify that such instruments can produce comparable results to those from existing ground level neutron monitors, and potentially enhance existing global capabilities. As proof of concept, a network of two instruments will be demonstrated as part of a test deployment, to provide a compatible data stream for incorporation into the Met Office Space Weather Operations Centre (MOSWOC) and feed into the airborne radiation modelling being developed as part of SWIMMR N2, the NERC funded SWIMMR Aviation Risk Modelling (SWARM) project. Ultimately GLEEM aims to construct and operate a significantly cheaper instrument, re-introduce monitoring in the UK and facilitate a major increase in space weather monitoring worldwide.