Publications
Abstract AniMAIRE (Anisotropic Model for Atmospheric Ionising Radiation Effects) is a new model and Python toolkit for calculating radiation dose rates experienced by aircraft during anisotropic solar energetic particle events. AniMAIRE expands the physics of the MAIRE + model such that dose rate calculations can be performed for anisotropic solar energetic particle conditions by supplying a proton or alpha particle rigidity spectrum, a pitch angle distribution, and the conditions of Earth's magnetosphere. In this paper, we describe the algorithm and top‐level structure of AniMAIRE and showcase AniMAIRE's capabilities by analyzing the dose rate maps that AniMAIRE produces when the time‐dependent spectra and pitch angle distribution for Ground Level Enhancement (GLE) 71 are input. We find that the dose rates AniMAIRE produces for the event fall between the dose rates produced by the WASAVIES and CRAC:DOMO models. Dose rate maps that evolve throughout the event are also shown, and it is found that each peak in the input pitch angle distribution generates a dose rate hotspot in each of the polar regions. AniMAIRE has been made available openly online so that it can be downloaded and run freely on local machines and so that the space weather community can easily contribute to it using Github forking. Plain Language Summary Solar particle events occur when particles are accelerated in eruptions on the Sun. If these particles hit Earth and have enough energy, they can penetrate Earth's magnetosphere and atmosphere, creating radiation showers that increase the radiation in Earth's atmosphere. When such increases are detected by neutron monitors at sea level, they are known as Ground‐Level Enhancements (GLEs), which occur once a year on average. GLEs can cause issues in aircraft electronics and cause passengers and crew on airplanes to experience heightened radiation doses. In this paper, we describe a new model to calculate radiation dose rates in the atmosphere during GLEs, called AniMAIRE. Most models that exist to date are only able to calculate radiation dose rates when all particles are hitting Earth equally from all directions, however this approximation is only reliable during the later stages of events, and isn't accurate for many GLEs. AniMAIRE has been designed so it doesn't need to rely on this approximation, and can calculate dose rates for situations where it is supplied a direction‐dependent particle flux, as well as those independent of direction. AniMAIRE has been tested across a GLE in May 2012, showing the direction dependent approach is necessary. Key Points AniMAIRE can simulate atmospheric radiation and electronics effects from anyinput anisotropic distribution of particles hitting Earth Anisotropy is important in the event‐integrated dose calculation for GLE71 according to AniMAIRE AniMAIRE has been made openly available online, such that anyone can run and experiment with it, or contribute to the model through forking
Ground level enhancements (GLEs) are space weather events that pose a potential hazard to the aviation environment through single event effects in avionics and increased dose to passengers and crew. The existing ground level neutron monitoring network provides continuous and well-characterized measurements of the radiation environment. However, there are only a few dozen active stations worldwide, and there has not been a UK-based station for several decades. Much smaller neutron detectors are increasingly deployed throughout the world with the purpose of using secondary neutrons from cosmic rays to monitor local soil moisture conditions (COSMOS). Space weather signals from GLEs and Forbush decreases have been identified in COSMOS data. Monte Carlo simulations of atmospheric radiation propagation show that a single COSMOS detector is sufficient to detect the signal of a medium-strength (10%–100% increase above background) GLE at high statistical significance, including at fine temporal resolution. Use of fine temporal resolution would also provide a capability to detect Terrestrial Gamma Ray Flashes (via secondary neutrons) which are produced by certain lightning discharges and which can provide a hazard to aircraft, particularly in tropical regions. We also show how the COsmic-ray Soil Moisture Observing System-UK detector network could be used to provide warnings at the International Civil Aviation Organization “Moderate” and “Severe” dose rate thresholds at aviation altitudes, and how multiple-detector hubs situated at strategic UK locations could detect a small GLE at high statistical significance and infer crucial information on the nature of the primary spectrum.
1 hour resolution time series data from the Guildford Compact Neutron Monitor. Contains raw counts from each detector (CTS_MOD1, CTS_MOD2, CTS_UNMOD), pressure (PA), temperature (TA), and relative humidity (RH) data, and pressure-corrected counts for each detector (CTS_MOD1_CORR, CTS_MOD2_CORR, CTS_UNMOD_CORR).
Data from ground-level radiation monitors and cosmogenic nuclides are combined to a give a probability distribution for severe radiation events related to the well quantified event of 23 February 1956. Particle fluxes, single event effects rates and dose rates are calculated for ground-level and aerospace systems. The event of February 1956 would provide a challenge to air safety while more extreme events seen in historical records would challenge safety-critical ground systems. A new space weather hazard scale based on this event could be used to give rapid assessment of the radiation hazard using high latitude neutron monitor data.
Significant increases to the atmospheric radiation environment are recorded by a network of ground level neutron monitors as ground level enhancements (GLEs). These space weather phenomena pose a risk to aviation via single event effects in aircraft electronics and ionizing dose to passengers and crew. Under the UK Space Weather Instrumentation, Measurement, Modeling and Risk programme, we have developed a new model to provide nowcasts of the aviation radiation environment, including both the galactic cosmic ray (GCR) background and during GLE events. The Model for Atmospheric Ionising Radiation Effects (MAIRE+) uses multiple data sources to characterize primary GCR and GLE particle spectra and combines these with precalculated geomagnetic and atmospheric response matrices to predict particle fluxes from ground level to 20 km altitude across the entire globe. Two European neutron monitors (located at Oulu in Finland and Dourbes in Belgium) are used as the primary indicators of GLE intensity in order to maximize accuracy over UK airspace. Outputs from MAIRE+ for the historical GLEs in September and October 1989 are compared to recalibrated empirical data from a solid‐state detector that was carried on Concorde in that period. The model will be hosted in the UK and will provide additional capability to the Met Office Space Weather Operations Center (MOSWOC). Plain Language Summary Ionizing radiation in the atmosphere is primarily caused by galactic cosmic rays (GCR) interacting with the upper atmosphere, creating showers of secondary radiation. At aviation altitudes the radiation environment is hundreds of times more intense than that experienced at the ground level. This relatively stable background level of radiation is punctuated by space weather events called ground level enhancements (GLEs), when energetic solar protons arrive at Earth and lead to elevated atmospheric radiation levels that can be orders of magnitude greater than background levels. Under the UK Space Weather Instrumentation, Measurement, Modeling and Risk programme, we have developed a new model to provide nowcasts of the aviation radiation environment, including both the GCR background and during GLE events. Through our Model for Atmospheric Ionising Radiation Effects, we show how data from ground level neutron monitors can be used to characterize the atmospheric radiation environment from ground level to 20 km altitude across the entire globe. Key Points The new Model for Atmospheric Ionising Radiation Effects (MAIRE+) is presented MAIRE+ uses neutron monitor data, sunspot number, Kp, and geostationary proton flux to nowcast the aviation radiation environment Model outputs are compared to data from a solid‐state detector carried on board Concorde during ground level enhancements in 1989
The upper atmosphere is a transition region between the neutron-dominated aviation environment and satellite environment where primary protons and ions dominate. We report high altitude balloon measurements and model results characterising this radiation environment for single event effects (SEE) in avionics. Our data, from the RaySure solid-state radiation monitor, reveal markedly different altitude profiles for low linear energy transfer (LET) and high LET energy depositions. We use models to show that the difference is caused by the influence of primary cosmic ray particles, which induce counts in RaySure via both direct and indirect ionization. Using the new Model of Atmospheric Ionizing Radiation Effects (MAIRE), we use particle fluxes and LET spectra to calculate single event upset (SEU) rates as a function of altitude from ground level to the edge of space at 100 km altitude. The results have implications for a variety of applications including high altitude space tourism flights, UAVs and missions to the Martian surface.