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Xiaochun He

Publications and source records attributed to Xiaochun He.

4 recordsLinked to original sources

Machine Learning-Ready Data Sets for the Analysis and Nowcasting of Atmospheric Radiation at Aviation Altitudes

Nowcasting and forecasting of the radiation environment in the Earth's lower atmosphere are critical for the safety of aircraft and spacecraft crews and passengers. Currently, this problem is addressed by employing statistical and physics-based models that take into account particle transport and precipitation. However, given the increased number of radiation measurements available to the community, it is possible to start developing data-driven approaches. We prepared Machine Learning-ready (ML-ready) datasets to nowcast the effective dose rates at aviation altitudes. The presented datasets contain 92,476 individual measurements from 589 flights obtained by the Automated Radiation Measurements for Aerospace Safety (ARMAS) experiment from 2013 to 2023. The ARMAS measurements are augmented with the properties of the Geospace environment, such as solar soft X-ray and proton fluxes, solar wind properties, secondary cosmic ray neutrons, space weather indexes, and global solar activity indicators (such as daily sunspot number). ARMAS data are separated into three partitions, ensuring that (1) the data points from a single flight remain within the same partition, and (2) each partition samples the flight locations and Geospace environment conditions equally. Several versions of the datasets allow predictions based on point-in-time measurements and use up to 24 hours of Geospace parameter history. The test of the use case demonstrates a possibility of nowcasting ARMAS measurements with accuracies slightly better than the considered physics-based models. The publicly available ML-ready datasets could serve as the first step in data preparation for ML-driven nowcasting and forecasting of the radiation environment.

physics.ao-ph

Novel Simulation Framework for Analyzing Cosmic Ray Particle Distributions at a Global Scale

Cosmic ray measurements have inspired numerous interesting applications over several decades worldwide. These applications encompass non-invasive cosmic ray muon tomography, which enables the imaging of concealed dense objects or structures, the monitoring of area-averaged soil moisture with cosmic ray neutrons in agriculture and climate studies, real-time monitoring of the dynamical changes of the space and earth weather, etc. The demand for a quantitative characterization of cosmic ray shower particles near the Earth's surface is substantial, as it provides realistic particle spectra and rates for these diverse applications. In this study, we introduce Earth Cosmic Ray Shower (ECRS), a GEANT4-based software designed to simulate cosmic ray particle interactions in the atmosphere. ECRS incorporates the U.S. Standard Atmospheric Model and integrates a time-dependent geomagnetic field based on the Tsyganenko and IGRF models. Additionally, we present two case studies illustrating variations in the location-dependent average particle energy for muons, electrons, neutrons, and gammas at sea level. An outlook of this project is provided toward the conclusion.

astro-ph.HE

Computational Challenges and Opportunities of Simulating Cosmic Ray Showers at Global Scale

Galactic cosmic rays are the high-energy particles that stream into our solar system from distant corners of our Galaxy and some low energy particles are from the Sun which are associated with solar flares. The Earth atmosphere serves as an ideal detector for the high energy cosmic rays which interact with the air molecule nuclei causing propagation of extensive air showers. In recent years, there are growing interests in the applications of the cosmic ray measurements which range from the space/earth weather monitoring, homeland security based on the cosmic ray muon tomography, radiation effects on health via air travel, etc. A simulation program (based on the GEANT4 software package developed at CERN) has been developed at Georgia State University for studying the cosmic ray showers in atmosphere. The results of this simulation study will provide unprecedented knowledge of the geo-position-dependent cosmic ray shower profiles and significantly enhance the applicability of the cosmic ray applications. In the paper, we present the computational challenges and the opportunities for carrying out the cosmic ray shower simulations at the global scale using various computing resources including XSEDE.

physics.comp-ph

Understanding the Effect of Atmospheric Density on the Cosmic Ray Flux Variations at the Earth Surface

We report in this letter for the first time the numerical simulations of muon and neutron flux variations at the surface of the earth with varying air densities in the troposphere and stratosphere. The simulated neutron and muon flux variations are in very good agreement with the measured neutron flux variation in Oulu and the muon flux variation in Atlanta. We conclude from this study that the stratosphere air density variation dominates the effects on the muon flux changes while the density variation in troposphere mainly influences the neutron count variation. These results pave a new path for systematically studying the global temperature evolution using worldwide cosmic ray data.

physics.ao-ph