Galactic Cosmic Ray Particles Research Articles

Initial Results of Low Earth Orbit Space Radiation Dosimeter on Board the Next Generation Small Satellite-2

As human exploration goals shift from missions in low Earth orbit (LEO) to long-duration interplanetary missions, radiation protection remains one of the key technological issues that must be resolved. The low Earth orbit space radiation dosimeter (LEO-DOS) instrument to measure radiation levels and create a global dose map in the LEO on board the the next generation small satellite-2 (NEXTSat-2) was launched successfully on May 25, 2023 using the Nuri KSLV-III in Korea. The NEXTSat-2 orbits the Earth every 100 minutes, in an orbit with an inclination of 97.8° and an altitude of about 550 km above sea level. The LEO-DOS is equipped with a particle dosimeter (PD) and a neutron spectrometer (NS), which enable the measurement of dosimetric quantities such as absorbed dose (D), dose equivalent (H) for charged particles and neutrons. To verify the observations of LEO-DOS, we conducted a radiation dose estimation study based on the initial results of LEO-DOS, measured from June 2023 to September 2023. The study considered four source categories: (i) galactic cosmic ray particles; (ii) the South Atlantic Anomaly region of the inner radiation belt (IRB); (iii) relativistic electrons and/or bremsstrahlung in the outer radiation belt (ORB); and (iv) solar energetic particle (SEP) events.

Advancing Precision Particle Background Estimation for Future X-Ray Missions: Correlated Variability between the Alpha Magnetic Spectrometer and Chandra/XMM-Newton

Galactic cosmic-ray (GCR) particles have a significant impact on the particle-induced background of X-ray observatories, and their flux exhibits substantial temporal variability, potentially influencing background levels. In this study, we present 1 day binned high-energy reject rates derived from the Chandra-ACIS and XMM-Newton EPIC-pn instruments, serving as proxies for the GCR particle flux. We systematically analyze the ACIS and EPIC-pn reject rates and compare them with the AMS proton flux. Our analysis initially reveals robust correlations between the AMS proton flux and the ACIS/EPIC-pn reject rates when binned over 27 day intervals. However, a closer examination reveals substantial fluctuations within each 27 day bin, indicating shorter-term variability. Upon daily binning, we observe finer temporal structures in the data sets, demonstrating the presence of recurrent variations with periods of ∼25 days and 23 days in the ACIS and EPIC-pn reject rates, respectively, spanning the years 2014–2018. Notably, during the 2016–2017 period, we additionally detect periodicities of ∼13.5 days and 9 days in the ACIS and EPIC-pn reject rates, respectively. Intriguingly, we observe a time lag of ∼6 days between the AMS proton flux and the ACIS/EPIC-pn reject rates during the second half of 2016. This time lag is not visible before 2016 and after 2017. The underlying physical mechanisms responsible for this time lag remain a subject of ongoing investigation.

Galactic Cosmic Ray Particle Exposure Does Not Increase Protein Levels of Inflammation or Oxidative Stress Markers in Rat Microglial Cells In Vitro.

Astronauts on exploratory missions will be exposed to galactic cosmic rays (GCR), which can induce neuroinflammation and oxidative stress (OS) and may increase the risk of neurodegenerative disease. As key regulators of inflammation and OS in the CNS, microglial cells may be involved in GCR-induced deficits, and therefore could be a target for neuroprotection. This study assessed the effects of exposure to helium (4He) and iron (56Fe) particles on inflammation and OS in microglia in vitro, to establish a model for testing countermeasure efficacy. Rat microglia were exposed to a single dose of 20 cGy (300 MeV/n) 4He or 2 Gy 56Fe (600 MeV/n), while the control cells were not exposed (0 cGy). Immediately following irradiation, fresh media was applied to the cells, and biomarkers of inflammation (cyclooxygenase-2 [COX-2], nitric oxide synthase [iNOS], phosphorylated IκB-α [pIκB-α], tumor necrosis factor-α [TNFα], and nitrite [NO2-]) and OS (NADPH oxidase [NOX2]) were assessed 24 h later using standard immunochemical techniques. Results showed that radiation did not increase levels of NO2- or protein levels of COX-2, iNOS, pIκB-α, TNFα, or NOX2 compared to non-irradiated control conditions in microglial cells (p > 0.05). Therefore, microglia in isolation may not be the primary cause of neuroinflammation and OS following exposures to helium or iron GCR particles.

ARAMIS: a Martian radiative environment model built from GEANT4 simulations

A new model of the Martian surface radiative environment has been built: Atmospheric RAdiation Model for Ionizing spectra on martian Surface (ARAMIS). Based on Monte Carlo calculations, it offers high computational flexibility for surface flux spectra with several GEANT4 physics lists tested for different exposures and mission scenarios. ARAMIS performs Monte Carlo simulations independently of any exposure scenario to determine a surface response function that can then be convolved to any input spectrum, avoiding simulation repetition while maintaining results accuracy, using a parametric atmosphere geometry. In particular, the adopted approach enables secondary spectra to be discriminated by type and origin, in order to observe the impact of different primary flux components on the surface dose calculation. The ARAMIS model has been validated with experimental measurements from the RAD (Radiation Assessment Detector) instrument on board the Mars Science Laboratory (MSL) Curiosity rover, and benchmarked against other models in the literature. Built using version 11.1.0 of the GEometry ANd Tracking (GEANT4) toolbox and established models of Galactic Cosmic Ray (GCR) or Solar Particle Event (SEP) spectra, the surface neutron and photon spectra provided by ARAMIS show a better agreement than other models with high-energy experimental data, reducing model uncertainty for radiation protection calculations.

Global dose distributions of neutrons and gamma-rays on the Moon

Dose assessment on the lunar surface is important for future long-term crewed activity. In addition to the major radiation of energetic charged particles from galactic cosmic rays (GCRs), neutrons and gamma-rays are generated by nuclear interactions of space radiation with the Moon’s surface materials, as well as natural radioactive nuclides. We obtained neutron and gamma-ray ambient dose distributions on the Moon using Geant4 Monte Carlo simulations combined with the Kaguya gamma-ray spectrometer measurement dataset from February 10 to May 28, 2009. The neutron and gamma-ray dose rates varied in the ranges of 58.7–71.5 mSv/year and 3.33–3.76 mSv/year, respectively, depending on the lunar geological features. The lunar neutron dose was high in the basalt-rich mare, where the iron- and titanium-rich regions are present, due to their large average atomic mass. As expected, the lunar gamma-ray dose map was similar to the distribution of natural radioactive elements (238U, 232Th, and 40K), although the GCR-induced secondary gamma-ray dose was significant at ~ 3.4 mSv/year. The lunar secondary dose contribution resulted in an additional dose of 12–15% to the primary GCR particles. Global dose distributions on the lunar surface will help identify better locations for long-term stays and suggest radiation protection strategies for future crewed missions.

Estimation of the neutron monitors’ effective energies based on the 27-day galactic cosmic rays variations

We presented a new method of the neutron monitors’ (NM’s) effective energy estimation based on the 27‑day galactic cosmic rays (GCR) variations: using AMS-02 measurements we study rigidity dependance of 27-day variations’ amplitude and calculate the energy value so that the variability of the GCR particles at this energy is equal to that of the NM’s count rate. We examined how NM’s effective energy depends on the geomagnetic cutoff rigidity using data of several NM.

Modeling the Radiation Environment of Energetic Particles at Mars Orbit and a First Validation against TGO Measurements

Sending astronauts to Mars will be a milestone of future deep space exploration activities. However, energetic particle radiation in deep space and in the Mars environment is a major risk to the health of future human explorers. The nominal Martian surface radiation field contains primary Galactic Cosmic Ray (GCR) particles and secondary particles generated in the Martian atmosphere and the regolith. Some of these secondary particles may propagate upward and even be detected at the orbit of Mars contributing to the orbit radiation. Studying the Mars orbit radiation environment is critical for planning future Mars orbital missions. Therefore, we calculate the Martian orbit radiation dose rate considering the primary GCR spectra provided by the Badhwar-O’Neill 2014 model and the secondary particles modeled by the state-of-the-art Atmospheric Radiation Interaction Simulator. Specifically, we calculate the integral dose rate of each particle type and its dependence on orbit height, surface pressure, and solar modulation intensity. Our analysis shows that modulation intensity is the most dominating factor and that different surface pressures make less than a 1% impact. We also derive the sensitive energy range of detected particles contributing to the dose rate and further validate our prediction against the measured data by Liulin-MO on TGO at a circular orbit around Mars. This may conduce to predicting the radiation risks in Mars orbit and providing constructive reference parameters for the crewed space industry.

SPACE RADIATION-INDUCED BYSTANDER EFFECT IN ESTIMATING THE CARCINOGENIC RISK DUE TO GALACTIC COSMIC RAYS

Space radiobiology is an interdisciplinary science that examines the biological effects of ionizing radiation on humans involved in aerospace missions. The knowledge of the risk assessment of the health hazard related to human space exploration is crucial to reducing damages induced to astronauts from Galactic Cosmic Rays (GCRs) and sun-generated radiation. GCRs have been identified as one of the primary sources of radiation exposure in space. In this context, an accurate characterization of the possible risk of carcinogenesis induced by exposure to GCRs particles is mandatory for safe human space exploration, and one of the most crucial open problems is the contribution to carcinogenesis due to the effects on the cells directly and not directly irradiated, indicated as Target Effects (TEs) and Non-Target Effects (NTEs), respectively. It is accepted that the detrimental effects of ionizing radiation are not restricted only to the irradiated cells but also to non-irradiated distant cells manifesting various biological effects. Tumor Prevalence (TP) is often used to investigate the effects of NTEs in predictions of chronic GCR exposure risk. This paper reports the status of the research on this topic at the INFN Roma Sapienza Alpha Magnetic Spectrometer (AMS) research group, where is in progress an extensive study about the risk evaluation of the NTEs that the GCRs radiation will imply when added to the TE. A theoretical framework is presented for TP-induced NTEs modeling, ready to be used with the data collected from the AMS02 detector. Finally, a possible example of the use of the tool is shown for an accurate estimate of the tumor prevalence function of the exposure period for different typical space protons energies.

Galactic Cosmic Rays at Mars and Venus: Temporal Variations from Hours to Decades Measured as the Background Signal of Onboard Microchannel Plates

A microchannel plate (MCP) is a component widely used for counting particles in space. Using the background counts from MCPs on the Mars Express and Venus Express orbiters—operating over 17 yr and 8 yr, respectively—we investigated the galactic cosmic ray (GCR) characteristics of the inner solar system. The MCP background counts at Mars and Venus, on a solar cycle timescale, exhibited clear anticorrelation with the sunspot number. We concluded that the measured MCP background counts contained GCR information. The GCR characteristics measured using the MCP background counts at Mars showed features consistent with measurements on Earth in Solar Cycle 24. The time lag between the sunspot number and the MCP background counts was found to be ∼9 months at Mars. The shorter-term background data recorded along the orbits (with a timescale of several hours) also showed evident depletion of the background counts, due to absorption of the GCR particles by the planets. Thanks to the visible planetary size change along an orbit, we developed a model to separate the GCR contribution to the MCP background counts from the internal contribution caused by the β-decay of radioactive elements in the MCP glass. Our statistical analysis of the GCR absorption signatures at Mars implies that the effective absorption radius of Mars for the GCR particles is >100 km larger than the radius of the planet. However, the cause remains an open question.

Temporal evolution and rigidity dependence of the solar modulation lag of Galactic cosmic rays

When traveling in the heliosphere, Galactic cosmic rays (GCRs) are subjected to the solar modulation effect, a quasiperiodical change of their intensity caused by the 11-year cycle of solar activity. Here we investigate the association of solar activity and cosmic radiation over five solar cycles, from 1965 to 2020, using a collection of multichannel data from neutron monitors, space missions, and solar observatories. In particular, we focus on the time lag between the monthly sunspot number and the GCR flux variations. We show that the modulation lag is subjected to a 22-year periodical variation, ranging from about 2 to 14 months and following the polarity cycle of the Sun's magnetic field. We also show that the lag is remarkably decreasing with increasing energy of the GCR particles. These results reflect the interplay of basic physics phenomena that cause the GCR modulation effect: the drift motion of charged particles in the interplanetary magnetic field, the latitudinal dependence of the solar wind, the energy dependence of their residence time in the heliosphere. Based on this interpretation, we end up with a global effective formula for the modulation lag and testable predictions for the flux evolution of cosmic particles and antiparticles over the solar cycle.

A New Model for Nowcasting the Aviation Radiation Environment With Comparisons to In Situ Measurements During GLEs

AbstractSignificant 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).

From the Top of Martian Olympus to Deep Craters and Beneath: Mars Radiation Environment Under Different Atmospheric and Regolith Depths

AbstractIn preparation for future human habitats on Mars, it is important to understand the Martian radiation environment. Mars does not have an intrinsic magnetic field and Galactic cosmic ray (GCR) particles may directly propagate through and interact with its atmosphere before reaching the surface and subsurface of Mars. However, Mars has many high mountains and low‐altitude craters where the atmospheric thickness can be more than 10 times different from one another. We thus consider the influence of the atmospheric depths on the Martian radiation levels including the absorbed dose, dose equivalent and body effective dose rates induced by GCRs at varying heights above and below the Martian surface. The state‐of‐the‐art Atmospheric Radiation Interaction Simulator based on GEometry And Tracking Monte Carlo method has been employed for simulating particle interactions with the Martian atmosphere and terrain. We find that higher surface pressures can effectively reduce the heavy ion contribution to the radiation, especially the biologically weighted radiation quantity. However, enhanced shielding (both by the atmosphere and the subsurface material) can considerably enhance the production of secondary neutrons which contribute significantly to the effective dose. In fact, both neutron flux and effective dose peak at around 30 cm below the surface. This is a critical concern when using the Martian surface material to mitigate radiation risks. Based on the calculated effective dose, we finally estimate some optimized shielding depths, under different surface pressures (corresponding to different altitudes) and various heliospheric modulation conditions. This may serve for designing future Martian habitats.

Global planetary ionization maps in Regener-Pfotzer cosmic ray maximum for GLE 66 during magnetic superstorm of 29–31 October 2003

High-energy particles of cosmic origin e.g. cosmic ray protons and heavier nuclei of galactic and/or solar origin induce complicated nuclear-electromagnetic-meson cascades in the Earth’s atmosphere, eventually leading to an ionization of the ambient air. The induced by cosmic rays atmospheric ionization is related to possible effect of precipitating particles on atmospheric physics and chemistry. These effects can be considerably enhanced during strong and moderately strong solar proton events. While the contribution of galactic cosmic ray particles to ion production in the atmosphere is slightly variable throughout a solar cycle, relativistic solar particles could produce a significant excess on ion pair production, particularly over polar caps. This effect is strong on a short time scales. On the other hand, depressions of the galactic cosmic ray flux, that is, Forbush decreases, can significantly impact the galactic cosmic ray induced ionization. The sequence of three ground level enhancements observed in October-November 2003, specifically the second: GLE 66 which occurred during a giant Forbush decrease, provides unique opportunity to study impact ionization on extended time scale, explicitly considering the reduced galactic cosmic ray flux. Using Monte Carlo simulations we computed the ion production rate and the corresponding ionization effect in the Earth atmosphere during GLE 66 occurred on 29 October 2003, explicitly considering the Forbush decrease and the complex geomagnetospheric conditions.

Cosmic-ray flux predictions and observations for and with Metis on board Solar Orbiter

Context.The Metis coronagraph is one of the remote sensing instruments hosted on board the ESA/NASA Solar Orbiter mission. Metis is devoted to carry out the first simultaneous imaging of the solar corona in both visible light (VL) and ultraviolet (UV). High-energy particles can penetrate spacecraft materials and may limit the performance of the on-board instruments. A study of the galactic cosmic-ray (GCR) tracks observed in the first VL images gathered by Metis during the commissioning phase is presented here. A similar analysis is planned for the UV channel.Aims.We aim to formulate a prediction of the GCR flux up to hundreds of GeV for the first part of the Solar Orbiter mission to study the performance of the Metis coronagraph.Methods.The GCR model predictions are compared to observations gathered on board Solar Orbiter by the High-Energy Telescope in the range between 10 MeV and 100 MeV in the summer of 2020 as well as with the previous measurements. Estimated cosmic-ray fluxes above 70 MeV n−1have been also parameterized and used for Monte Carlo simulations aimed at reproducing the cosmic-ray track observations in the Metis coronagraph VL images. The same parameterizations can also be used to study the performance of other detectors.Results.By comparing observations of cosmic-ray tracks in the Metis VL images with FLUKA Monte Carlo simulations of cosmic-ray interactions in the VL detector, we find that cosmic rays fire only a fraction, on the order of 10−4, of the whole image pixel sample. We also find that the overall efficiency for cosmic-ray identification in the Metis VL images is approximately equal to the contribution ofZ ≥ 2 GCR particles. A similar study will be carried out during the whole of the Solar Orbiter’s mission duration for the purposes of instrument diagnostics and to verify whether the Metis data and Monte Carlo simulations would allow for a long-term monitoring of the GCR proton flux.

Calculating the Rate of Ionization during a GLE Event with a Global Model of Earth’s Atmosphere and Estimating of the Contribution to this Process from Galactic Cosmic Ray Particles with Z > 2

Calculating the Rate of Ionization during a GLE Event with a Global Model of Earth’s Atmosphere and Estimating of the Contribution to this Process from Galactic Cosmic Ray Particles with Z > 2

Study of transient modulation of galactic cosmic rays due to interplanetary manifestations of coronal mass ejections: 2010 - 2017

We study the transient modulation of galactic cosmic rays (GCRs) due to coronal mass ejections (CMEs) and their associated structures detected during most part of solar cycle 24. The interplanetary counterpart of CMEs (ICMEs), while propagating in the interplanetary space, may be associated with the shock/sheath region. An ICME may (or may not) be the so-called magnetic cloud. Using the method of superposed-epoch analysis, we analyze cosmic-ray neutron monitor data together with various plasma and magnetic field data during the passage of interplanetary structures with distinct plasma and magnetic field properties. From a detailed analysis of plasma and magnetic field variations during the passage of the shock/sheath/magnetic cloud/non-magnetic cloud ejecta, together with the cosmic-ray neutron monitor data, we conclude that the high magnetic field regions are particularly effective in modulating the GCRs when the field inside them is high and turbulent also. Our results agree with the hypothesis that the transient decreases/Forbush decreases in GCRs are mainly caused by turbulent high field regions due to the scattering of the GCR particles.

Long‐Term Observations of Galactic Cosmic Ray LET Spectra in Lunar Orbit by LRO/CRaTER

AbstractThe Cosmic Ray Telescope for the Effects of Radiation (CRaTER) has been orbiting the Moon since 2009 aboard the Lunar Reconnaissance Orbiter (LRO). From this vantage point, it samples the interplanetary energetic particle population outside the shielding of the Earth's magnetosphere. We report the sensor's observations of galactic cosmic rays (GCRs) over a complete solar activity cycle. CRaTER is designed primarily to measure not the spectra of GCR particles outside the sensor but rather their effects on matter, and in particular, it measures the linear energy transfer (LET) or energy‐deposit spectrum in its silicon detectors. We have used the Geant4 radiation‐transport code to devise a background‐rejection algorithm to improve these measurements of LET under 9.9 g/cm2 of shielding, and the resulting observations show the changing radiation effects of GCRs as their intensity and spectrum vary with solar modulation. As of 2020 this intensity, after declining during solar maximum activity, has recovered to a level that exceeds by a few percent the historically high values seen during the deep solar minimum at the start of the LRO mission in 2009.

Radiation dose and its protection in the Moon from galactic cosmic rays and solar energetic particles: at the lunar surface and in a lava tube

The lunar surface is directly and continuously exposed to Galactic Cosmic ray (GCR) particles and Solar energetic particles (SEPs) due to the lack of atmosphere and lunar magnetic field. These charged particles interact with the lunar surface materials producing secondary radiations such as neutrons and gamma rays. In a departure from precise GCR and SEP data, we estimated the effective dose equivalent at the lunar surface and in a lunar lava tube in this paper by using PHITS, a Monte Carlo simulation tool. The effective dose equivalent due to GCR particles at the lunar surface reached 416.0 mSv yr−1 and that due to SEPs reached 2190 mSv/event. On the other hand, the vertical hole of the lava tube provides significant radiation protection. The exposure by GCR particles at the bottom of the vertical hole with a depth of 43 m was found to be below 30 mSv yr−1 while inside a horizontal lava tube, the value was less than 1 mSv yr−1 which is the reference value for human exposure on the Earth. We expect that the lunar holes will be useful components in the practical design of a lunar base to reduce radiation risk and to expand mission terms.

Absorbed doses from GCR and albedo particles emitted by the lunar surface

When high energy galactic cosmic ray (GCR) particles collide with the lunar regolith, they eject “albedo” particles from the surface. The albedo particles could be either scattered incident ions, or secondary ions and neutrons produced by the collisions of incident ions with the lunar regolith. In an effort to understand the nature of these albedo particles, we use the MCNP6 transport code to estimate the angular and energy distribution of albedo particles at an altitude of 50 km to calculate the resulting total absorbed dose rates, which are compared with measurements from the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) instrument aboard the Lunar Reconnaissance Orbiter (LRO) spacecraft. MCNP6 simulations estimate that the albedo particles account for 19.9% of the total absorbed dose rate. The albedo photons account for 8.81% of the total absorbed dose rate, the highest among albedo species followed by protons (4.97%), electrons (2.47%), positrons (1.89%), neutrons (1.17%), deuterons (0.5%), tritium ions (0.07%), helium-3 ions (0.02%), and alphas (0.01%). In addition, recent studies indicate the presence of hydrogen on the Moon. We simulate a hypothetical lunar regolith enriched with hydrogen to study its effect on the lunar albedo. The results herein show that the proton absorbed dose rate is slightly increased if hydrogen is present in the regolith, which is primarily caused by the increased flux of energetic albedo protons leaving the lunar surface.

Effects of solar activity on production rates of short‐lived cosmogenic radionuclides

AbstractThe solar activity can be quantified by solar modulation parameter Φ that affects the heliospheric magnetic field. This activity influences the intensity of the galactic cosmic ray (GCR) particle flux within the solar system, and consequently, the differential primary particle spectra depend on the solar modulation parameter Φ (MeV). The modulation parameter Φ shows spatial and temporal variations (Leya and Masarik 2009). Some of the solar activity variations are cyclic and result in measurable effects as for example the 11‐year solar cycle. Variations in solar activity only induce small effects on the production of long‐lived cosmogenic radionuclides. This is due to the fact that activities measured in meteorites usually correspond to saturation values and represent long‐term average values. Long‐lived radionuclides often require millions of years of irradiation by GCR to reach saturation and therefore activity cycles average out. In contrast, one can expect strongly pronounced variations for saturation values caused by primary flux intensity variations, if short‐lived radionuclides with half‐lives ranging from days to a few years are investigated. Short‐lived cosmogenic nuclides were the subject of many experimental and theoretical investigations (e.g., Evans et al. 1982; Spergel et al. 1986; Neumann et al. 1997; Komura et al. 2002; Laubenstein et al. 2012). The aim of this work is to develop formulae for calculating production rates of radionuclides with short half‐life, taking into account temporal variations in the primary cosmic ray intensity. The developed formulae were applied to the Kosice and Chelyabinsk meteorites. The results for the Košice meteorite were already published (Povinec et al. 2015). Here, we give a full explanation of underlying model.