arXiv subjects

Keith Ryden

Publications and source records attributed to Keith Ryden.

3 recordsLinked to original sources

arXiv2025

Background in Low Earth Orbiting Cherenkov Detectors, and Mitigation Strategies

Cherenkov detectors have been used in space missions for many decades, and for a variety of purposes, including for example, for Galactic Cosmic Ray (GCR) and Solar Energetic Particle (SEP) measurements. Cherenkov detectors are sensitive to many types of particles that are present in the environment of space, including gamma rays, trapped particles and cosmic particles, and each particle component acts as essentially a background when trying to view another specific particle component. In this research, GRAS/Geant4 simulations were performed to characterise the count rates that a simple Cherenkov detector design would experience in a low Earth orbit, and we find that Cherenkov count rates due to most particle components vary significantly depending on many different factors, including the location in the orbit, the date of the orbit, whether or not the detector is within the van Allen belts, and whether or not a solar particle event is occurring. We find that a small Cherenkov detector is readily able to gather detailed data on both trapped particles and spectral information during Ground-Level Enhancements. We also investigate the use of coincidence as a method to remove count rates due to trapped particles and delta electrons, finding that this method is generally very effective for resolving count rates due to GLEs amongst intense trapped particle environments, but that some Cherenkov count rates due to trapped particles are still observed in the simulated south Atlantic anomaly region.

physics.ins-det↗

arXiv2024

AniMAIRE -- A New Openly Available Tool for Calculating Atmospheric Ionising Radiation Dose Rates and Single Event Effects During Anisotropic Conditions

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 analysing the dose rate maps that AniMAIRE produces when the time-dependent spectra and pitch angle distribution for GLE71 are inputted. 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 inputted 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.

physics.app-ph↗

arXiv2022

The Variation of Radiation Effective Dose Rates and Single Event Effect Rates at Aviation Altitudes with Magnetospheric Conditions and Geographic Location

The geographic structure of radiation dose rates at aircraft altitudes in Earth's atmosphere during the irradiation of Earth by proton spectra from incoming solar particle events is examined using the recently developed MAIRE+ software. Conditions are examined under two incoming proton spectra, a low/hard spectral index and a high/soft spectral index spectra, which are representative of some of the solar particle events that have caused reasonably sized Ground-Level Enhancements/Events (GLEs) over the past 70 years. It is found through the use of `cut-throughs' of the atmosphere, that the atmosphere can be divided into three volumes; a high dose rate polar region, a low dose rate equatorial region, and a transition region between the two. The location of these regions as a function of latitude, longitude and altitude is characterised. It is also found that the location of the transition region changes for different magnetospheric disturbance levels, implying that the total radiation dose rate an aircraft will experience if it passes through the transition region will be subject to large systematic uncertainties, particularly during the currently unknown levels of magnetospheric disturbance that a major solar event could cause. The impact that various magnetospheric conditions might have on dose rates that specific flight routes might experience is also discussed.

physics.app-ph↗