MOSAIC Digital Environment Feasibility Study

There is growing awareness of the hazards arising from space weather which are now listed on the UK National Risk Register (Cabinet Office, 2018). One significant risk is created by 'hard' solar particle events containing a significant flux of highly energetic particles which can lead to corruption and damage in modern microelectronic technology at ground level. In general such solar events are detectable at the earth's surface by ground level neutron monitors and are termed ground level enhancements (GLEs): they typically have durations of some hours and the most intense ever measured was in February 1956 in the UK. Prior to the 1940s however we have only indirect measurements of GLEs from ice cores and tree rings (Miyake et al, 2012; Mekhaldi et al, 2015). Results on 10Be, 36Cl and 14C show events some 30 times larger than February 1956 in AD774 and 15 times larger in AD994. In today's technological society GLEs present a hazard to complex systems, such as autonomous vehicles, railways, nuclear power stations and especially aircraft (including unmanned aerial platforms) which are by far the most exposed. At present the UK has no ground level neutron measurement capability as this was abandoned in the 1980s. The main objective of the Moisture Sensors for Atmospheric Ionising Collaboration (MOSAIC) project is to study dual-purposing the UK COSMOS soil moisture sensor network to provide an unprecedented, high-density, sustainable and cost-effective UK space weather measurement capability to provide real-time alerts for critical infrastructure as well as enabling new environmental science. COSMOS is a relatively new and expanding network of sensors and there are now nearly 50 detectors across the UK operated by the NERC Centre for Ecology and Hydrology (CEH). Neutrons generated by cosmic-rays high in the atmosphere can reach ground level, some of which will be reflected dependent on the soil moisture content: COSMOS stations measure the reflected neutrons to determine average soil moisture over the local area. Besides studying the prospect of operational warnings for infrastructure (including aviation) there is an opportunity to create a long term record of ground level neutron radiation in the UK which can be the basis of better environmental models and improved risk assessments for government.

The study examine COSMOS sensitivity to GLEs along with the digital network feasibility issues which would arise when dual-purposing the network. An initial priority is to examine the practicality of significantly higher temporal resolution which will be needed for MOSAIC given that GLE rise times can be of the order of minutes. We will examine the feasibility of achieving very rapid communication of data from the sensors to the centre(s) where decisions are taken on the need to issue alerts and how long this might take. It is likely that the geographical diversity and distributed nature of the COSMOS digital network could offer significant benefits for robustness via the inherent redundancy compared to conventional 'single point' monitors. To assist this work the Met Office will act as the primary 'user' of the system and will advise on their data distribution and processing requirements and we will investigate how artificial intelligence can better distinguish the wanted signal and enhance decision accuracy. We will also investigate how MOSAIC can be integrated with the Surrey Smartphone Atmospheric Ionising RAdiation network or SAIRA which has already demonstrated a citizen science approach to obtain complementary radiation data from aircraft.

The dual-purposing of COSMOS-UK as proposed in MOSAIC has the potential to create an unprecedented capability to measure the UK ground level radiation environment arising from cosmic rays and GLEs (the latter occurring on average once per year) and to ultimately build a long term record. This data will underpin future science to understand propagation of extremely energetic particles from sun to earth and their interactions with the geomagnetic field. This will lead to a better definition of the threats to infrastructure which in turn will enable a specification of reasonable worst case environments against which government departments such as BEIS and Department for Transport (DfT) can judge societal resilience. Equally important, the study could lead to the provision of real-time alerts to key infrastructure such as nuclear power, railways and aviation. The need for such alerts has already been identified by key national companies and agencies such as EDF who, in the context of their existing and new-build UK nuclear reactors, are supporting this study since they need a GLE detection system but one which does not require major new detector installations or infrastructure. The aviation sector has also clearly identified the need for similar alerts and hence MOSAIC has the potential to improve the safety of UK aviation during periods of severe space weather by providing coherent and timely risk information. The UK Met Office is the national risk owner for space weather and fully supports this study since it is acutely aware of a serious information gap for UK aviation regarding atmospheric radiation which MOSAIC can help fill. Likewise this study will have a considerable impact with the Civil Aviation Authority, the UK National Air Traffic Service (NATS) and DfT who are preparing plans for how to respond to GLEs: the absence of UK neutron monitoring is a key gap.

In addition the improved understanding of the impact of cosmic ray variations and GLEs on soil moisture measurements which will be gained from this project will greatly assist the soil moisture community itself since at present space weather variations cause errors in soil moisture measurements. Furthermore UK 'homeland security' activities searching for rogue nuclear materials should also benefit since subtraction of cosmic ray 'noise' signals is a continuous challenge and sudden solar particle increases could give false alarms.

While this study is UK-focussed there is ultimately the potential to consider whether at least part of the global COSMOS could also be dual-purposed, in which case the above impacts would be scaled up accordingly. In addition ground level neutron bursts from TGFs may be detectable by COSMOS and will be considered in this study - if so then MOSAIC could lead to a new means of capturing these mysterious events since at present there is no distributed in-situ observation network available.

Our project partners (who include end users such as Met Office and EDF Energy) are vital to achieving the required impacts, as is the Stakeholder Advisory Group which will include an even wider set of interested parties (such as Civil Aviation Authorities and Nuclear Regulatory bodies). We will prepare a number papers for refereed academic journals which will have impact in both the space weather and hydrological communities given the novel approach considered. In addition we will engage in outreach with the media who we anticipate will find the project unusual and exciting for news purposes.