Measurements of Cosmic Proton Flux through Neutron Monitors Using Deep Networks and Imputation Techniques in the AMS-02 Era

Since 2013, continuous monitoring of spatial-angular distribution of CRs for each hour of measurements has been carried out at SHICRA SB RAS, using data from the international neutron monitor database NMDB and the method of real-time global survey. For this purpose, nine parameters of the CR distribution are automatically calculated which result from the first two angular moments of the spatial distribution function of particles in interplanetary space. Our earlier studies have shown that before the onset of most geomagnetic storms with the amplitude of the geomagnetic activity Dst index lower than –50 nT there is a sharp increase in amplitudes of north-south components of CR distribution. This can serve as a predictor of the onset of geomagnetic disturbances with a lead time from several hours to 1–2 days. This paper presents the results of forecasting of geomagnetic storms with a Dst amplitude <–50 nT, observed in April–November 2024. It is also shown that the appearance of false predictors is associated with Earth’s entry into large-scale SW disturbances without geomagnetic effects.

Since 2013, continuous monitoring of spatial-angular distribution of CRs for each hour of measurements has been carried out at SHICRA SB RAS, using data from the international neutron monitor database NMDB and the method of real-time global survey. For this purpose, nine parameters of the CR distribution are automatically calculated which result from the first two angular moments of the spatial distribution function of particles in interplanetary space. Our earlier studies have shown that before the onset of most geomagnetic storms with the amplitude of the geomagnetic activity Dst index lower than –50 nT there is a sharp increase in amplitudes of north-south components of CR distribution. This can serve as a predictor of the onset of geomagnetic disturbances with a lead time from several hours to 1–2 days. This paper presents the results of forecasting of geomagnetic storms with a Dst amplitude <–50 nT, observed in April–November 2024. It is also shown that the appearance of false predictors is associated with Earth’s entry into large-scale SW disturbances without geomagnetic effects.

The role of chlorine as a neutron poison and as a seed for producing radioactive waste in nuclear systems has driven a renewed interest to improve its nuclear data uncertainties. Additionally, basic and applied science programs that use CLYC (Cs_2LiYCl_6:Ce) detectors for neutron spectroscopy and monitoring are also very sensitive to any change in chlorine nuclear data for simulations of the detector response. In this work, sensitivities relevant for these different applications are addressed through simulations of the efficiency of CLYC detectors in a fast fission spectrum when applying new chlorine nuclear data as input. These simulations are validated by an experimental measurement using CLYC detectors coupled to an ionization chamber loaded with a ^{252}Cf spontaneous fission source. The results are then used to obtain the first reliable direct measurement of the ^{35}Cl(n,p_0) and summed ^{35}Cl(n,p+n,alpha) fission spectrum average cross sections, found to be 54.7(32) and 105.0(98) mb, respectively. The results are within uncertainty of calculated fission spectrum averaged cross sections based on recently re-evaluated chlorine nuclear data, which confirm recent impact studies performed for the Molten Chloride Reactor Experiment. Meanwhile, there currently exists only one published criticality benchmark experiment that is sufficiently sensitive to chlorine nuclear data. Discrepancies are found with this set of criticality safety benchmarks, which are more sensitive to thermal and epithermal neutron energies than the energies, above 100 keV, tested in this current work. Hence, there is still a need to re-evaluate the chlorine nuclear data at lower energies to assess these discrepancies. Interpretation of the data from future “faster” criticality benchmarks, which are needed for next-gen fast reactor designs, benefit from the improved constraints on the chlorine nuclear data validated in this work.

Modelization of the MiniCaLMa neutron monitor based on Geant4 and Garfield++

This article explores the temporal dynamics and fractal characteristics of cosmic ray (CR) intensity by conducting a comprehensive analysis of their intrinsic scaling properties. The study utilizes sophisticated methodologies, including standard Detrended Fluctuation Analysis (DFA) and the Multifractal DFA (MF-DFA) approach to robustly evaluate long-memory, self-similarity, and singularity spectra within extensive CR time series. By systematically investigating measurements from two neutron monitor stations with long data archives, the analysis demonstrates the prevalence of multifractal behavior with persistent long-range correlations. Building on the fractal regime revealed in CR time series, this work utilizes the Natural Time Analysis (NTA) tool that is based in the order of occurrence of the extreme cosmic ray events (ECREs). The operational utility of this tool is demonstrated through a case analysis of CR fluctuations during the severe geomagnetic disturbances observed from 9 to 15 May 2024, capturing early-warning signatures and complex temporal responses. Furthermore, the Modified NTA (M-NTA) is used to estimate the occurrence rate of future ECREs. Our findings contribute to a deeper understanding of the scaling laws governing CR intensity and their potential for improving the ECRE modeling, with direct implications for space weather risk mitigation and solar–terrestrial interactions.

Abstract This study investigates how cosmic ray intensity (CRI) responds to major geomagnetic storms in 2024, utilizing data from six high‐latitude neutron monitor (NM) stations and solar wind parameters from the OMNI database. An event‐aligned Superposed Epoch Analysis (SEA) framework, using 2‐day windows centered at the Dst minimum, consistently reveals Forbush Decreases (FDs) in CRI, with onset timing and depth influenced by storm intensity and station location. A strong inverse correlation between CRI and the Akasofu parameter () indicates that cosmic ray access to near‐Earth space decreases as solar wind energy input increases. The pressure‐corrected Dst index () also shows significant anti‐correlation with CRI, consistent with enhanced geomagnetic shielding during ring current intensification. Wavelet Transform Coherence analysis confirms statistically significant coupling between CRI and , , the Alfvén Mach number, and the magnetosonic Mach number (MMN), especially within the 6–24 hr period range. During superstorms, coherence is intense and persistent, with and MMN leading CRI suppression at diurnal scales. Rigidity‐dependent analysis shows that peak CRI depression increases at lower cutoff rigidities, supporting the role of geomagnetic filtering during storm conditions. These findings show that a combination of solar wind drivers and internal magnetospheric dynamics shapes storm‐time CRI responses.

Abstract The Boron Neutron Capture Therapy (BNCT) irradiation field comprises high-intensity neutrons and gamma-rays that need to be measured separately because of their different biological effects. To conduct appropriate quality assurance (QA), we should measure the neutrons and gamma-rays. In a previous study, an air-ionization chamber combined with a fiber-type neutron monitor was constructed for QA. However, the fibers attached to the chamber were perturbed by neutron scattering. To eliminate the effect of perturbations, we developed an air ionization chamber into which the fiber could be inserted. Irradiation tests in the BNCT irradiation field showed that the perturbation effect was reduced by less than half, and it was confirmed that the system could measure neutrons and gamma-rays simultaneously for weekly QA. The sensitivity of the chamber to neutron energy was evaluated via simulations, and it was found that corrections for sensitivity to high-energy neutrons are required.

Abstract. Ground-level enhancements (GLEs) provide crucial insights into the acceleration and transport of solar energetic particles (SEPs). We present a comprehensive analysis of GLE 72, which occurred on 10 September 2017, coinciding with a solar-wind stream interaction region (SIR) impacting Earth's magnetosphere. By combining multi-station neutron monitor observations with a focused transport model constrained by solar-wind data, we investigate how the SIR modulates the observed GLE pulse shape. Our analysis reveals that the turbulent magnetic field within the SIR significantly enhances pitch angle scattering rates, with the diffusion coefficient increasing by up to 200 % during the 6 h SIR crossing. This leads to a 60 % increase in the particle mean free path across the SIR. Our model successfully reproduces the observed gradual rise phase (>8 h) and prolonged decay, demonstrating that even moderate interplanetary disturbances can substantially alter SEP transport conditions. Our results challenge the traditional impulsive–gradual classification of GLEs, highlighting the need to consider interplanetary transport effects when interpreting these events. The findings of this study highlight the importance of integrating multi-point observations and advanced modelling to disentangle particle acceleration and transport processes in the complex medium of solar wind.

Abstract The flux of galactic cosmic rays (GCRs) is modulated by solar activity on different time scales. This is often described with the force‐field approximation via the single variable parameters of the modulation parameter, which formally corresponds to the average rigidity loss of GCR particles in the heliosphere. The force‐field approximation is usually assumed to work properly only for periods of a solar rotation (27 days) or longer. However, daily values of the modulation parameter have been constructed based on ground‐based neutron monitor (NM) data suggesting that this approach might work reasonably well also on shorter time scales. Here we check this by simulating the daily GCR proton fluxes using the force‐field approach and the daily modulation parameter reconstructions, and confronting them with the daily proton‐flux measurements by the AMS‐02 onboard the International Space Station. A polynomial regression between the simulated and measured fluxes is proposed for longer‐term analyses and interpolations. For mid‐rigidities from 5–15 GV, the agreement is accurate within and slightly worsens toward higher rigidities, likely because of smaller statistics. We also found a lingering solar‐cycle trend at lower energies between the data and the model and the effect of the solar magnetic field polarity. These findings can be used for the utilization of the force‐field approach for short‐term variations.

1D Slow Neutron Monitor Based on RPC with 10B4C

Intercomparison of personal and ambient neutron detectors used for radiation protection in a synchrotron-based proton therapy facility: experimental and Monte Carlo results.

An optical fiber-based neutron detector is a real-time neutron monitor for an intense neutron field. A small piece of neutron scintillator, such as Ce-doped lithium glass (Li-glass), used in the detector has a random shape with a grain size of 200–400 μm. This causes shape-dependent effects on the detector response. However, it is difficult to control or determine its shape due to its small size. Here we propose a technique to characterize the fine structure of a small piece of scintillator using a microcomputed tomography (CT) system. To verify accuracy, the mass calculated based on the density of Li-glass and the volume extracted from the obtained CT image was compared to the mass measured in advance using an electronic balance. In the obtained CT images, the fine shape of the small piece of Li-glass was clearly visible, and no false signals from the surrounding components were observed. The calculated mass was in good agreement with the measured value, however, when the total number of projection images was 2000, a slight underestimation was observed. This was mitigated by increasing the number of projection images, and the difference between the calculated and measured mass was 1.6% when the number of the projection images was 3141. This was equivalent to the uncertainty of the measured mass. The proposed technique will be useful when high accuracy is needed, such as for medical applications.

BackgroundCurrently, the metal foil activation method is routinely used to measure the neutron output of an accelerator‐based neutron source designed for clinical Boron neutron capture therapy (BNCT). Although this method is well established and has been primarily utilized since the nuclear reactor BNCT era, the process is labour‐intensive and not well‐suited for a busy hospital environment performing routine patient treatment. A replacement neutron detector system that is simple to use and can measure the neutron output in real‐time is necessary.PurposeInvestigation and implementation of an Eu doped LiCaAlF6 scintillator detector for use in routine quality assurance tests of an accelerator‐based neutron source designed for clinical BNCT.MethodsThe response of the scintillator detector was evaluated using the NeuCure BNCT system installed at the Kansai BNCT Medical Center. The measurement repeatability, neutron fluence linearity, and neutron flux dependency of the detector system were evaluated. The beam central axis and off‐axis thermal neutron distribution inside a water phantom were measured and compared with the Monte Carlo treatment planning system (TPS).ResultsThe scintillator detector system showed high measurement repeatability with a coefficient of variation of less than 0.4%. The detector system showed linear response up to a proton charge of 3.6 C, and the response was stable between a proton current of 0.1 and 1 mA. Both the central axis and off‐axis thermal neutron flux inside a water phantom matched closely with both the metal foil activation method and the Monte Carlo simulation results. The time it took to perform a routine quality assurance test was drastically reduced from 1.5 h down to a few minutes.ConclusionImplementation of this detector system in the clinic would significantly reduce the time required for routine QA, acceptance, and commissioning, and be a stepping stone to assist expansion of accelerator‐based BNCT systems worldwide.

Neutron monitors (NMs), located at different points on the planet, allow us to study the time, energy, and angular characteristics of galactic and solar particle fluxes. Since NMs are located inside Earth's magnetosphere, their response depends on their location on the planet's surface, which can be characterized by the geomagnetic cutoff rigidity. Its calculation depends on the magnetic field model, the date, and even on numerical methods. The paper presents calculated geomagnetic cutoff rigidities at the locations of some neutron monitors and compares the cutoff values with the calculation results obtained by other authors, including a comparison of the time dynamics over the past decade. We show that the geomagnetic cutoff rigidities obtained for 2020 by the IGRF-14 model differ from those derived by IGRF-13; however, for 2015 the difference between the models is negligible. We demonstrate a tendency for the geomagnetic cutoff rigidity to decrease over time, especially at midlatitudes. Comparison of the obtained geomagnetic cutoff rigidities with those obtained by other authors has shown that in most cases the difference does not exceed 0.2 GV. Such discrepancies are significant only in the circumpolar region, where particles are mostly shielded by Earth’s atmosphere rather than by the geomagnetic field. We show that the accuracy of the algorithm in use is comparable to that of other existing instruments and is sufficient for calculating neutron monitor responses.

Neutron monitors (NMs), located at different points on the planet, allow us to study the time, energy, and angular characteristics of galactic and solar particle fluxes. Since NMs are located inside Earth's magnetosphere, their response depends on their location on the planet's surface that can be characterized by the geomagnetic cutoff rigidity. Its calculation depends on the magnetic field model, the date, and even on numerical methods. The paper presents calculated geomagnetic cutoff rigidities at the locations of some neutron monitors, and compares the cutoff values with the calculation results obtained by other authors, including a comparison of the time dynamics over the past decade. We show that the geomagnetic cutoff rigidities obtained for 2020 by the IGRF-14 model differ from those derived by IGRF-13; however, for 2015 the difference between the models is negligible. We demonstrate a tendency for the geomagnetic cutoff rigidity to decrease over time, especially at midlatitudes. Comparison of the obtained geomagnetic cutoff rigidities with those obtained by other authors has shown that in most cases the difference does not exceed 0.2 GV. Such discrepancies are significant only in the circumpolar region, where particles are mostly shielded by Earth’s atmosphere rather than by the geomagnetic field. We show that the accuracy of the algorithm in use is comparable to that of other existing instruments and is sufficient for calculating neutron monitor responses.

Abstract. Cosmic ray neutron sensors (CRNSs) are state-of-the-art tools for field-scale soil moisture measurements, yet uncertainties persist due to traditional methods for estimating scaling parameters that lack the capacity to account for site-specific and sensor-specific characteristics. This study introduces a novel, data-driven approach to estimate key scaling parameters (beta, psi, and omega) by directly calculating scaling parameters from measurement data, emphasizing local environmental factors and sensor attributes. The method demonstrates reliability and robustness, with strong correlations between estimated scaling parameters and environmental factors such as cutoff rigidity, latitude, and elevation, as well as consistency with semi-analytical traditional methods, e.g. for beta an R2 of 0.46. The study also reveals systematically higher variability in calibration parameters than previously assumed, underscoring the importance of this new method, of data quality, and of the careful selection of Neutron Monitor Database (NMDB) reference sites. The new method reduces RMSE by up to 25 %, with differences in soil moisture estimates between traditional and data-driven methods reaching 0.04 m3 m−3 and up to 0.12 m3 m−3 under certain conditions. Sensitivity analysis shows that soil moisture estimation is most influenced by scaling parameters in the wet end of the soil moisture spectrum. By improving the accuracy of CRNS data, this approach enhances soil moisture estimation and supports better decisions in agriculture, hydrology, and climate monitoring. Future research should focus on refining these scaling methods and enhancing data quality to further improve CRNS measurement accuracy.

This paper benchmarks two Proportional Technologies, Inc. (PTI) boron-coated straw (BCS) detector offerings against commercial helium-3 (3He) detectors for ground-level neutron monitoring. This study aims to assess if BCS-based detectors are a viable detector choice for the construction of a cosmic ray neutron monitor (NM) that is less expensive, smaller and produces comparable results to the 6-tube NM-64, typically used in the existing global NM network. The experimental methodology, data and analysis for the observed detection efficiency of the PTI-110 BCS module as a function of distance are presented. The PTI-204 BCS detector tube is benchmarked against a 7.5[Formula: see text]atm 3He-filled cylindrical proportional counter using a high-density polyethylene (HDPE) moderating test rig. Monte Carlo N-Particle (MCNP) models are validated against the experimental data. The experimental and simulation data for PTI-110 BCS unit detection efficiency agreement is within 4.5%. This confirms that the response of charged particles from the B4C layer is accounted for. The measured 3He tube detection efficiency was nearly three times greater than the PTI-204 detector. A trade-off analysis of 3He (at various fill pressures) versus BCS-based detector options, with supporting experimentally validated MCNP calculations, is used to provide confidence in the calculation of the 4 atm 3He tube-based ground-level NM design.

Abstract During their propagation in the heliosphere, interplanetary coronal mass ejections (ICMEs) interact with galactic cosmic ray (GCR) particles, modifying their spectrum and driving anisotropies. We analyze the first large Forbush decrease (FD) of Solar Cycle 25 on 2021 November 3–5 by using multipoint in situ observations and neutron monitors to study the association between FD characteristics and ICME. We use the Grad–Shafranov reconstruction to infer the magnetic field configuration of the ICME. We model the neutron monitor response through primary spectrum and anisotropy. The primary spectrum is parameterized with the force-field approximation and the anisotropy is modeled through a spherical harmonic expansion. We optimize the model parameters during the FD by using ground-based observations provided by the worldwide neutron-monitor network. The model’s results are compared with space-based measurements of the differential proton flux measured by the HEPD-01 detector on board the CSES-01 satellite and of the integral counts of both the High-Energy Particle Detector (HEPD-01) and the High Energy Telescope on board the Solar Orbiter. Anisotropy develops during the ICME passage, within the magnetic flux rope (MFR) and is found to be bidirectional. The force-field parameterization of the primary GCR fluxes based on ground-based measurements is found to be in very good agreement with spacecraft observations in the sub-GeV range. The GCR anisotropy obtained by fitting the model to ground-based observations is consistent with interplanetary magnetic field observations. The results suggest that the local magnetic field has a substantial axial component that is aligned to the MFR axis, and determines the GCR anisotropy at the typical neutron monitor energies.

Abstract Observations of temporary Forbush decreases (FDs) in the Galactic cosmic-ray (GCR) flux due to the passage of solar storms are useful for space-weather studies and alerts. Here, we introduce techniques that use global networks of ground-based neutron monitors and muon detectors to measure variations of GCR rigidity spectra in space during FDs by (1) fitting count rate decreases for power-law rigidity spectra in space with anisotropy up to second order and (2) using the “leader fraction” derived from a single neutron monitor. We demonstrate that both provide consistent results for hourly spectral index variations for five major FDs, and they agree with daily space-based data when available from the Alpha Magnetic Spectrometer. We have also made the neutron monitor leader fraction publicly available in real time. This work verifies that ground-based observations can be used to precisely monitor GCR spectral variation over a wide range of rigidities during space-weather events, with results in real time or from short-term postanalysis.