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The origin of high-energy galactic cosmic rays is yet to be understood, but some galactic cosmic-ray accelerators can accelerate cosmic rays up to PeV energies. The high-energy cosmic rays are expected to interact with the surrounding material or radiation, resulting in the production of gamma-rays and neutrinos. To optimize for the detection of such associated production of gamma-rays and neutrinos for a given source morphology and spectrum, a multimessenger analysis that combines gamma-rays and neutrinos is required. In this study, we use the Multi-Mission Maximum Likelihood framework with IceCube Maximum Likelihood Analysis software and HAWC Accelerated Likelihood to search for a correlation between 22 known gamma-ray sources from the third HAWC gamma-ray catalog and 14 yr of IceCube track-like data. No significant neutrino emission from the direction of the HAWC sources was found. We report the best-fit gamma-ray model and 90% CL neutrino flux limit from the 22 sources. From the neutrino flux limit, we conclude that, for five of the sources, the gamma-ray emission observed by HAWC cannot be produced purely from hadronic interactions. We report the limit for the fraction of gamma-rays produced by hadronic interactions for these five sources. [ABSTRACT FROM AUTHOR]

X-rays have significant impacts on cold, weakly ionized protoplanetary disks by increasing the ionization rate and driving chemical reactions. Stellar flares are explosions that emit intense X-rays and are the unique source of hard X-rays with an energy of ≳10 keV in the protoplanetary disk systems. Hard X-rays should be carefully taken into account in models as they can reach the disk midplane as a result of scattering in the disk atmospheres. However, previous models are insufficient to predict the hard X-ray spectra because of simplifications in flare models. We develop a model of X-ray spectra of stellar flares based on observations and flare theories. The flare temperature and nonthermal electron emissions are modeled as functions of flare energy, which allows us to better predict the hard X-ray photon flux than before. Using our X-ray model, we conduct radiative transfer calculations to investigate the impact of flare hard X-rays on disk ionization, with a particular focus on the protoplanetary disk around a T Tauri star. We demonstrate that for a flare with an energy of 1035 erg, X-ray photons with ≳5 keV increase the ionization rates more than galactic cosmic rays down to z ≈ 0.1 R. The contribution of flare X-rays to the ionization at the midplane depends on the disk parameters such as disk mass and dust settling. We also find that the 10 yr averaged X-rays from multiple flares could certainly contribute to the ionization. These results emphasize the importance of stellar flares on the disk evolution. [ABSTRACT FROM AUTHOR]

We present a survey of 1D kinetic particle-in-cell simulations of quasi-parallel nonrelativistic shocks to identify the environments favorable for electron acceleration. We explore an unprecedented range of shock speeds v sh ≈ 0.067–0.267 c, Alfvén Mach numbers M A = 5 – 40 , sonic Mach numbers M s = 5 – 160 , as well as the proton-to-electron mass ratios m i/ m e = 16–1836. We find that high Alfvén Mach number shocks can channel a large fraction of their kinetic energy into nonthermal particles, self-sustaining magnetic turbulence and acceleration to larger and larger energies. The fraction of injected particles is ≲0.5% for electrons and ≈1% for protons, and the corresponding energy efficiencies are ≲2% and ≈10%, respectively. The extent of the nonthermal tail is sensitive to the Alfvén Mach number; when M A ≲ 10 , the nonthermal electron distribution exhibits minimal growth beyond the average momentum of the downstream thermal protons, independently of the proton-to-electron mass ratio. Acceleration is slow for shocks with low sonic Mach numbers, yet nonthermal electrons still achieve momenta exceeding the downstream thermal proton momentum when the shock Alfvén Mach number is large enough. We provide simulation-based parameterizations of the transition from thermal to nonthermal distribution in the downstream (found at a momentum around p i , e / m i v sh ≈ 3 m i , e / m i ), as well as the ratio of nonthermal electron to proton number density. The results are applicable to many different environments and are important for modeling shock-powered nonthermal radiation. [ABSTRACT FROM AUTHOR]

The article "Unraveling the Mystery of Lightning Superbolts" explores the phenomenon of superbolts, which are lightning strikes at least 1,000 times more powerful than ordinary lightning. These superbolts have been detected over oceans and are concentrated in specific regions, such as the North Atlantic and the Andes. Researchers have found correlations between superbolts and factors like the Earth's magnetic field, cosmic rays, and cloud formation. Despite their rarity, superbolts are a fascinating natural occurrence that scientists continue to study. [Extracted from the article]

The present study is a preliminary step towards the detection of cosmic rays at higher altitude in the Great Himalayan range. Present work is an attempt to see the possibility of the presence of cosmic rays at a height of 3800 m from the sea level in the Great Himalayan range. An experiment was planned for the search of galactic cosmic rays (GCR) using CR39 track etch detectors at the Patsio DRDO (Defence Research and Development Organization) laboratory in the Great Himalayan range, India at a height of 3800 m from the sea level and 32° 45′ N, 77° 15′ E. CR39 detectors were etched in 8N NaOH solution + 3% ethyl alcohol at 70 °C to visualize the tracks produced in the exposed detectors under optical microscope. A detection threshold of CR39 detector down to Z = 18 (Z/β ~ 27) was obtained. After scanning, fine tracks were observed and it was concluded that that high Z cosmic rays may be present at an altitude of 3800 m from the sea level in the Great Himalayan range. [ABSTRACT FROM AUTHOR]

Excesses of cosmic-ray produced nuclei in individual components of meteorites indicate "pre-irradiation", either in the surface region of their parent bodies or as free-floating small particles in the early Solar System. We expand on our earlier work (Beyersdorf-Kuis et al., 2015) and report a study of cosmic-ray produced He and Ne in chondrules and "matrix" (i.e., matrix-dominated) material of several CR2 and CV meteorites as well as the highly primitive, unique, carbonaceous chondrite Acfer 094. In accordance with previous work, no evidence for pre-irradiation was found for CV3 Allende, while for CV3 Vigarano evidence for pre-irradiation is marginal at best. Also, the single chondrule from unique Acfer 094 that we studied has a cosmic ray exposure indistinguishable from the one we found for "matrix" material. Chondrules from Acfer 082 (CV) exhibit both excesses and deficits relative to "matrix", which points to pre-irradiation of not only chondrules, but also matrix material. A similar case may be Renazzo (CR2), where, however, the identification is complicated by the presence of abundant pre-solar Ne-E. A large number of chondrules (ten) were studied from CR2 El Djouf 001, which yielded slightly variable, small but consistent, excesses relative to "matrix", corresponding to "nominal" (i.e., irradiation by galactic cosmic rays in 4π geometry) excess ages of 1–2 Ma. Modelling suggests contributions from irradiation in the parent body regolith by solar cosmic rays (SCR) as well as galactic cosmic rays (GCR), where the latter dominates. Reevaluating the large variations previously identified in chondrules from QUE 99177, we suggest either a very different regolith history compared to that of El Djouf 001 or, more likely, pre-irradiation by, primarily, GCR in the early solar system as suggested previously. The case of solar-wind-rich NWA 852 (CR2) shows similarity to El Djouf 001 except for a much larger size of the effects. We suggest that the situation may be common among meteorites with a regolith origin. With independent information on the cosmic ray exposure age, which could be obtained by the study of cosmic-ray produced radionuclides, the individual parent body contributions may be disentangled, providing constraints on regolith dynamics. [ABSTRACT FROM AUTHOR]

The Calorimetric Electron Telescope, CALET, is an astroparticle physics mission installed on the International Space Station, ISS. The primary objective of the mission is studying the details of galactic cosmic-ray acceleration and propagation, and searching for the possible nearby sources of high-energy electrons and dark matter signatures. The CALET experiment measure the flux of cosmic-ray electrons (including positrons) to 20 TeV, gamma-rays to 10 TeV and nuclei to 1000 TeV. The detector is an all-calorimetric instrument with a total vertical thickness of 30 radiation lengths and fine imaging capability, optimized for the measurement of the electron and positron (all-electron) spectrum well into the TeV energy region. It consists of a charge detector (CHD) with two layers of segmented plastic scintillators for the identification of cosmic-rays via a measurement of their charge over the range Z = 1 ∼ 40 , a 3 radiation length thick tungsten-scintillating fiber imaging calorimeter (IMC) and a 27 radiation length thick lead-tungstate calorimeter (TASC). The instrument was launched on August 19, 2015 to the ISS and installed on the Japanese Experiment Module-Exposed Facility. Since the start of operation in October, 2015, CALET has been collecting scientific data without any major interruption for more than eight years. The number of triggered events over 10 GeV is nearly 1.97 billion events as of November 30, 2023. In this paper, we present the results of the CALET mission so far, including the all-electron energy spectrum, the spectra of protons and other nuclei, gamma-ray observations, as well as the characterization of on-orbit performance. Some results on the electromagnetic counterpart search for LIGO/Virgo gravitational wave events and the observations of solar modulation and gamma-ray bursts are also included. [ABSTRACT FROM AUTHOR]

The accurate knowledge of cosmic ion fluxes is essential for fundamental physics, deep space missions, and exploration activities in the solar system. In the HelMod-4 model the Parker transport equation is solved using a Monte Carlo approach to evaluate the solar modulation effect on local interstellar spectra of Galactic Cosmic Rays (GCRs). This work presents the latest updates to the HelMod-4 model parameters, focusing on the descending phase of solar cycle 24. The updates are motivated by the latest high-precision measurements from the AMS-02 detector which revealed for the first time with high accuracy the features of GCR fluxes' evolution during a period of positive interplanetary magnetic field polarity. Furthermore, we present HelMod-4/CUDA , a GPU-accelerated approach for solving the Parker equation in the heliosphere using a stochastic differential equation method. The code is an evolution of the HelMod-4 code, porting the algorithm to GPU architecture using the CUDA programming language. This approach achieves significant speedup compared to a CPU implementation. The HelMod-4/CUDA code has been validated by comparing its results with the most precise and updated experimental GCR spectra observed during high and low solar activity periods, both in the inner and outer heliosphere, at the Earth location, and outside the ecliptic plane. The comparison shows that HelMod-4 and HelMod-4/CUDA can be equivalently used to provide solar-modulated spectra with a similar degree of accuracy in reproducing observed data. [ABSTRACT FROM AUTHOR]

The Near-Earth space environment is impacted by various radiation sources like galactic cosmic rays, solar storms, geomagnetic storms, etc. In the present paper, we have estimated the impact of space radiation observed during the last four cycles. We have observed that during solar cycle 24, there were fewer solar radiation storms than during its three preceding solar cycles. In terms of solar radiation storm strength, solar cycle 22 recorded a maximum intensity of S4 (severe radiation storm) of ~ 43000 pfu. In comparison, the maximum intensity of solar cycle 24 was ~ 6530 pfu (S3 type). We have concluded that the intensity of an X-class flare did not predict the intensity of the ensuing geomagnetic activity. The flares with less intensity in X-rays, e.g. M-class and C-class flares, can give rise to stronger radiation storms. Using the NOAA scales, we have compared the data of intense radiation storms with geomagnetic storms of higher intensity. This analysis has revealed that there were only 11 days during solar cycles 23 and 24 where the maximum solar radiation storm (solar particle event) coincided with a period of severe geomagnetic storming. On comparison of monthly neutron count (cosmic ray intensity) relative to the average of the last 20 years, we also deduced that the neutron count was 7.12% greater than usual during the most recent solar low, which was nearly as high as the last solar cycle lowest (8.20%). We have observed the lower probability rate of Solar Particle Events during the 3 or so years cantered on solar minimum, and the probability does not necessarily peak within a few years of solar maximum. The intensity of relativistic electrons observed by GOES in geostationary orbit was relatively low during periods of low geomagnetic activity and low solar wind speed, and the outer belt 2 MeV electrons flux appears to be highly associated with the Dst index. [ABSTRACT FROM AUTHOR]

A dilute plasma is continuously maintained in the troposphere by ionising particle radiation from galactic cosmic rays and radon decay. Small ions in the 1–2 nm size range play an important role in atmospheric processes such as ion-induced nucleation of aerosol particles. Consequently there is a need for precise and robust instruments to measure small ions both for atmospheric observations and for laboratory experiments that simulate the atmosphere. Here we describe the design and performance of the Cluster Ion Counter (CIC, Airel OÜ), which simultaneously measures the number concentrations of positively- and negatively-charged ions and particles below 5 nm mobility diameter, with low noise and fast time response. The detection efficiency is above 80 % for ions and charged particles between 1.2 and 2.0 nm, and above 90 % between 2.0 and 3.0 nm. The ion concentrations measured by the CIC agree well with reference instruments. The noise level (1 σ of background measurements) is typically between 20 and 30 ions cm-3 at 1 Hz sampling rate and an air flow rate of 7 l min-1 per analyzer. The noise level improves when higher flow rates and longer sampling periods are used. The CIC responds rapidly with 1 s time resolution to pulses of ionisation produced in the CLOUD chamber by a CERN particle beam. [ABSTRACT FROM AUTHOR]

A strong Forbush decrease, i.e., suppression of the flux of galactic cosmic rays recorded on Earth, was observed by the global network of ground-based neutron monitors (NMs) on 24 – 25 March 2024. The decrease was very unusual as characterised by so rapid recovery that a false Ground-level enhancement (GLE) alarm was produced by the corresponding warning systems. Here we present the first comprehensive collection and analysis of the available data for this event. The event was highly anisotropic as exhibited in a 3-h spread of the deep-phase timing for different NMs. The anisotropy was focused nearly at the anti-sunward direction with a narrow cone of 20 – 30 °. The heliospheric situation leading to this unusual Forbush decrease was quite complex. An analysis of first look records was performed, considering the stations acceptance, taking into account the complex geomagnetic conditions. A leader fraction analysis indicates that the recovery phase of the event was rigidity-independent and had essentially the same spectral shape as the pre-event period. A summary of the solar-terrestrial phenomena is provided to assist in future work on modelling this complex event. [ABSTRACT FROM AUTHOR]

The Fermi and eROSITA bubbles (FBs and eRBs), large diffuse structures in our Galaxy, can be the by-products of steady star formation activity. To simultaneously explain the star formation history of the Milky Way (MW) and the metallicity of ∼ Z ⊙ at the Galactic disk, a steady Galactic wind driven by cosmic rays (CRs) is required. For tenuous gases with a density of ≲10−3 cm−3, CR heating dominates over radiative cooling, and the gas can maintain the virial temperature of ∼0.3 keV, ideal for escape from the Galactic system as the wind. A part of the wind falls back onto the disk like a Galactic fountain flow. We model the wind dynamics according to the Galactic evolution scenario and find that the scale height and surface brightness of the X-ray and the hadronic gamma-ray emissions from such fountain flow region can be consistent with the observed properties of the FBs and eRBs. This implies that the bubbles are persistent structures of the MW existing over (at least) the last ∼1 Gyr rather than evanescent structures formed by nontrivial, ∼10 Myr past Galactic center transient activities. [ABSTRACT FROM AUTHOR]

The origin of Galactic cosmic rays (CRs) is unknown even though they have traditionally been connected to supernovae based on energetic arguments. In the past decades, Galactic black holes in X-ray binaries (BHXBs) have been proposed as candidate sources of CRs, which revises the CR paradigm. BHXBs launch two relativistic jets during their outbursts, but recent observations suggested that these jets may be launched even during quiescence. A0620−00 is a well-studied object that shows indications of jet emission. We study the simultaneous radio-to-X-ray spectrum of this source that was detected while the source was in quiescence to better constrain the jet dynamics. Because most BHXBs spend their lifetimes in quiescence (qBHXBs), we used the jet dynamics of A0620−00 to study a population of 105 such sources distributed throughout the Galactic disc, and a further 104 sources that are located in the boxy bulge around the Galactic centre. While the contribution to the CR spectrum is suppressed, we find that the cumulative intrinsic emission of qBHXBs from both the boxy bulge and from the Galactic disc adds to the diffuse emission that various facilities detected from radio to TeV γ rays. We examined the contribution of qBHXBs to the Galactic diffuse emission and investigated the possibility of SKA, INTEGRAL, and CTAO to detect individual sources in the future. Finally, we compare the predicted neutrino flux to the recently presented Galactic diffuse neutrino emission by IceCube. [ABSTRACT FROM AUTHOR]

Context. This study investigates the periodicities of galactic cosmic ray flux attributed to corotating interaction regions (CIRs) using Alpha Magnetic Spectrometer (AMS-02) data from late 2016 to early 2017. Aims. We determine the rigidity dependence of recurrent Forbush decrease (RFD) amplitudes induced by CIRs for different particles with a focus on charge sign. Methods. We carried out a frequency analysis using a Lomb-Scargle algorithm and superposed epoch analysis for all particles. For protons and helium, we compared the results with a single Forbush decrease (FD) analysis. Results. Our results reveal that the rigidity dependence of proton amplitudes attributed to the northern coronal hole is in qualitative agreement with previous findings. In contrast, the amplitudes attributed to the southern coronal hole show no rigidity dependence. Furthermore, the amplitude of the helium modulation exceeds that of protons, in line with the observation for long-term modulation. For positrons, statistical limitations stand in the way of any definitive conclusions. In comparison to the positively charged particles, the modulation behavior of electrons reveals a different pattern. [ABSTRACT FROM AUTHOR]

The Scibar Cosmic-Ray Telescope (SciCRT) is the most promising detector of the Sierra Negra Cosmic Rays Observatory (SN-CRO). At this location, being a target and a tracker of secondary cosmic rays, the SciCRT offers a high probability of observing solar energetic particles and lower energy galactic cosmic rays (LEGCR); also, it allows the identification of incoming particles by measuring their energy deposition. In this work we present a Geant4-based simulation of the energy deposited by neutrons, γ -rays, protons, electrons and muons in the optimally running SciCRT components. We also calculated the detection efficiency of the SciCRT at its current state. Our simulation results provide new information about the SciCRT detection response that may be used as a basis to estimate and analyze the energy spectra of primary particles. [ABSTRACT FROM AUTHOR]

The detection of various molecular species, including complex organic molecules relevant to biochemical and geochemical processes, in astronomical settings, such as the interstellar medium or the outer solar system, has led to the increased need for a better understanding of the chemistry occurring in these cold regions of space. In this context, the chemistry of ices prepared and processed at cryogenic temperatures has proven to be of particular interest due to the fact that many interstellar molecules are believed to originate within the icy mantles adsorbed on nano- and micro-scale dust particles. The chemistry leading to the formation of such molecules may be initiated by ionizing radiation in the form of galactic cosmic rays or stellar winds, and thus, there has been an increased interest in commissioning experimental setups capable of simulating and better characterizing this solid-phase radiation astrochemistry. In this article, we describe a new facility called AQUILA (Atomki-Queen's University Ice Laboratory for Astrochemistry), which has been purposefully designed to study the chemical evolution of ices analogous to those that may be found in the dense interstellar medium or the outer solar system as a result of their exposure to keV ion beams. The results of some ion irradiation studies of CH3OH ice at 20 K are discussed to exemplify the experimental capabilities of the AQUILA as well as to highlight its complementary nature to another laboratory astrochemistry setup at our institute. [ABSTRACT FROM AUTHOR]

As the current solar cycle 25 progresses and moves towards solar maxima, solar activity is increasing and extreme space weather events are taking place. Two severe geomagnetic storms accompanied by two large Forbush decreases in galactic cosmic ray intensity were recorded in March and May, 2024. More precisely, on 24 March 2024, a G4 (according to the NOAA Space Weather Scale for Geomagnetic Storms) geomagnetic storm was registered, with the corresponding geomagnetic indices Kp and Dst equal to 8 and −130 nT, respectively. On the same day, the majority of ground-based neutron monitor stations recorded an unusual Forbush decrease. This event stands out from a typical Forbush decrease because of its high amplitude decrease phase and rapid recovery phase, i.e., 15% decrease and an extremely rapid recovery of 10% within 1.5 h, as recorded at the Oulu neutron monitor station. Furthermore, on 10–13 May 2024, an unusual G5 geomagnetic storm (geomagnetic indices Kp = 9 and Dst = −412 nT) was registered (the last G5 storm had been observed in 2003). In addition, the polar neutron monitor stations recorded a Ground Level Enhancement (GLE74) during the recovery phase of a large Forbush decrease of 15%, which started on 10 May 2024. In this study, a detailed analysis of these two severe events in regard to the accompanying solar activity, interplanetary conditions and solar energetic particle events is provided. Moreover, the results of the NKUA "GLE Alert++ system", the NKUA/IZMIRAN "FD Precursory Signals" method and the NKUA "ap Prediction tool" concerning these events are presented. [ABSTRACT FROM AUTHOR]

This study delves into the investigation of cosmic-ray radiation exposure levels for workers and their impact on the signal correlation subsystems at the Atacama Large Millimeter/ submillimeter Array (ALMA) observatory sites. The analysis presents a detailed examination of secondary cosmic ray spectra and flux at the ALMA sites, encompassing the operational period from 2010 to the present day, with a particular focus on the consequences of extreme solar flares. In terms of radiation exposure for ALMA employees, the annual exposure at the highest site (AOS) reaches approximately 4.8 mSv. This value exceeds the exposure level of a typical nuclear fuel cycle worker or those working at high-altitude Antarctica stations. The exposure is approximately 2.7 times lower at the ALMA Operations Support Facility (OSF). Furthermore, the additional ambient dose equivalent resulting from solar events, while low for events similar to those observed since the 1950s, can reach up to approximately 1 mSv when considering more ancient solar events based on environmental archives. Our analysis includes radiation effects measurements in the Baseline Correlator at the AOS and, more generally, underscores the significance of employing accurate modeling and simulation techniques to assess the effects of galactic cosmic rays and extreme solar events on the integrated circuits utilized or planned in the ALMA correlation subsystem. [ABSTRACT FROM AUTHOR]

Understanding the hazards of space radiation is imperative as astronauts begin voyaging on missions with increasing distances from Earth's protective shield. Previous studies investigating the acute or long-term effects of specific ions comprising space radiation have revealed threats to organs generally considered radioresistant, like the brain, and have shown males to be more vulnerable than their female counterparts. However, astronauts will be exposed to a combination of ions that may result in additive effects differing from those of any one particle species. To better understand this nuance, we irradiated 4-month-old male and female, wild-type and Alzheimer's-like mice with 0, 0.5, or 0.75 Gy galactic cosmic ray simulation (GCRsim) or 0, 0.75, or 2 Gy gamma radiation (wild-type only). At 11 months, mice underwent brain and heart MRIs or behavioral tests, after which they were euthanized to assess amyloid-beta pathology, heart and kidney gene expression and fibrosis, and plasma cytokines. Although there were no changes in amyloid-beta pathology, we observed many differences in brain MRIs and behavior, including opposite effects of GCRsim on motor coordination in male and female transgenic mice. Additionally, several genes demonstrated persistent changes in the heart and kidney. Overall, we found sex- and genotype-specific, long-term effects of GCRsim and gamma radiation on the brain, heart, and kidney. [ABSTRACT FROM AUTHOR]

• 27-day variations of GCR flux according to measurements of AMS-02 and others. • Parameterization of the amplitude-energy spectrum of variations. • Consequences of the force-field model for short-term modulation. This work presents the results of the analysis of 27-day variations in the flux of galactic protons registered by STEREO, SOHO, and AMS-02 in 2015–2016. We calculate variations' amplitude using several different approaches and propose a description of its energy dependence in the range of magnetic rigidity from approximately 0.3 to 100 GV. We also analyse variations of the solar modulation potential, which is the only parameter of force-field model, and consider the possibility of describing the 27-day variations of galactic cosmic rays within the framework of this model. It is shown that rigidity dependence of the 27-day variations amplitude cannot be properly described using this simple approximation. [ABSTRACT FROM AUTHOR]

In this paper, we performed solar synodic period (∼27 days) and heliospheric effect for selected solar activity parameters: sunspot number (SSN), sunspot area (SSA), modified coronal index (MCI), solar radio flux (F10.7), chromospheric composite Mg II index and Galactic cosmic rays (GCRs), during the ascending phase of solar cycles 24 and 25 (2009–2012 and 2020 to 2023). The Wavelet analyses of daily data of SSN, SSA, MCI, Mg II, and F10.7, reveal a solar rotational period of ∼27 days. The R Robper method is used to validate the observed periods; near one solar rotational period during the ascending phase of solar cycles 24 and 25. We observed cross-correlation and time lag for solar activity parameters (SSN, SSA, MCI, Mg II, and F10.7) with GCRs during the ascending phase of solar cycles 24 and 25 (2009–2012 and 2020 to 2023). We found the highest time lag for SSA is ∼300 days, and for SSN is ∼270 days during the ascending phase of solar cycle 25. We also found the highest cross-correlation values are 0.998 and 0.996 for chromospheric composite Mg II index with Galactic cosmic rays (GCRs) during the ascending phase of solar cycle 24 and 25 respectively. We found the chromospheric composite Mg II index is a good indicator of solar activity indices and it is strongly correlated to SSN. [ABSTRACT FROM AUTHOR]

Galactic cosmic rays (GCRs) interact with matter in the atmosphere and at the surface of the Earth to produce a range of cosmogenic nuclides. Measurements of cosmogenic nuclides produced in surface rocks have been used to study past land ice extent as well as to estimate erosion rates. Because the GCR flux reaching the Earth is modulated by magnetic fields (solar and Earth's), records of cosmogenic nuclides produced in the atmosphere have also been used for studies of past solar activity. Studies utilizing cosmogenic nuclides assume that the GCR flux is constant in time, but this assumption may be uncertain by 30 % or more. Here we propose that measurements of 14 C of carbon monoxide (14 CO) in ice cores at low-accumulation sites can be used as a proxy for variations in GCR flux on timescales of several thousand years. At low-accumulation ice core sites, 14 CO in ice below the firn zone originates almost entirely from in situ cosmogenic production by deep-penetrating secondary cosmic ray muons. The flux of such muons is almost insensitive to solar and geomagnetic variations and depends only on the primary GCR flux intensity. We use an empirically constrained model of in situ cosmogenic 14 CO production in ice in combination with a statistical analysis to explore the sensitivity of ice core 14 CO measurements at Dome C, Antarctica, to variations in the GCR flux over the past ≈ 7000 years. We find that Dome C 14 CO measurements would be able to detect a linear change of 6 % over 7 ka, a step increase of 6 % at 3.5 ka or a transient 100-year spike of 190 % at 3.5 ka at the 3 σ significance level. The ice core 14 CO proxy therefore appears promising for the purpose of providing a high-precision test of the assumption of GCR flux constancy over the Holocene. [ABSTRACT FROM AUTHOR]

The updated database of Forbush effects and interplanetary disturbances (https://tools.izmiran.ru/feid) is used for an extensive analysis of various characteristics of events caused by the influence of interacting solar wind disturbances on the near-Earth space. In particular, the cases of different combinations of the pair interaction of high-speed streams from coronal holes and coronal mass ejections over the long period from 1995 to 2022 are considered. Variations in the flux of galactic cosmic rays (with a rigidity of 10 GV) and changes in the parameters of the interplanetary medium and geomagnetic activity are described. It is shown that the degree of mutual influence depends on the time between the detection of neighboring events; with the most pronounced changes in various parameters for events whose interaction occurred before reaching Earth's orbit. It is also established that in interacting solar wind disturbances not only the extremes of the parameters of cosmic rays, interplanetary medium, and geomagnetic activity but also their time profiles are subject to changes. [ABSTRACT FROM AUTHOR]

Gels are soft materials composed of hydrophilic polymers cross-linked in water by physical or chemical bonds. Due to their lightweight and water-rich nature, these materials find application in various fields, including the space environment, for radiation protection purposes. In fact, thanks to their high hydrogen content, gels exhibit significant radiation stopping power, resulting in reduced fragmentation of incident particles. This suggests their potential utility in shielding electronic devices and safeguarding astronauts' health. In this work, cross-linked gels based on poly(vinyl alcohol) (PVA) and boric acid (BA) were fabricated and their properties were investigated using different experimental and modeling techniques. The effect of parameters, such as time and temperature, used for fabricating the PVA/BA gels is assessed. Fourier transform infrared spectroscopy (FTIR) was employed to evaluate the ability of BA to form hybrid interpolymeric bonds with PVA macromolecules. To understand the thermo-mechanical properties and viscoelastic behavior of these gels, dynamic mechanical analysis (DMA) in compression mode was performed. The shielding properties were evaluated in different space radiation environments considering galactic cosmic rays, solar particle events, and low earth orbit radiation using deterministic transport codes. The High charge (Z) and Energy TRaNsport (HZETRN) code was employed to create different cross sections as first output for the selected materials, and then, propagate and transport the ionizing radiation inside the materials. The results highlight several advantages of PVA/BA gels fabricated at room temperature without heat treatments. Firstly, the incorporation of BA allows for a slight increase in water content compared to gels produced without the crosslinker. Additionally, an examination of elastic moduli reveals improved mechanical properties exhibiting approximately twice the elastic modulus of PVA gels. Moreover, the analysis of dosimetry quantities suggests that the radiation protection effectiveness of these gels is comparable to that of pure water, while heat-treated PVA/BA gels exhibit a reduced water content resulting in decreased shielding properties and decreased flexibility. Consequently, PVA/BA gels realized at room temperature appear to be the optimal material between PVA gels and the heat-treated counterparts, making them well-suited for integration into astronaut personal protective equipment. [Display omitted] • Cross-linked gels made of poly(vinyl alcohol) matrix and boric acid crosslinker are realized. • The coordinative bonds between boric acid and poly(vinyl alcohol) are determined by the Fourier transform infrared spectroscopy. • Boric acid greatly increases the mechanical properties of gels in terms of storage modulus. • The effectiveness of gels in radiation shielding has been demonstrated by numerical simulation carried out using HEZTRN2020 • Gels of poly(vinyl alcohol) and boric acid can be used in spacesuits of astronauts as personal protective equipment. [ABSTRACT FROM AUTHOR]

The method of the two neutron monitors was used to analyze the parameters of the rigidity spectrum variations (RSV) of galactic cosmic ray intensity (GCR) flux in solar cycle 24 based on the data from the global network of neutron monitors. This method is an alternative to the least squares method when there are few monitors working stably in a given period, and their use in the least squares method is impossible. Analyses of the changes in exponent γ in the RSV of GCR flux from 2009 to 2019 were studied. The soft RSV (γ = 1.2–1.3) of the GCR flux around the maximum epoch and the hard RSV (γ = 0.6–0.9) around the minimum epoch of solar activity (SA) is the general feature of GCR modulation in the GeV energy scale (5, 50), to which neutron monitors were found to correspond. Therefore, various values of the RSV γ in the considered period show that during the decrease and increase period of SA, the essential changes in the large-scale structure of the heliospheric magnetic field (HMF) fluctuations/turbulence take place. The exponent γ of the RSV of the GCR flux can be considered a significant parameter to investigate the long-period changes in the GCR flux. [ABSTRACT FROM AUTHOR]

We report Nd and Sm isotopic compositions of four samples of Ryugu returned by the Hayabusa2 mission, including "A" (first touchdown) and "C" (second touchdown) samples, and several carbonaceous chondrites to evaluate potential genetic relationships between Ryugu and known chondrite groups and track the cosmic ray exposure history of Ryugu. We resolved Nd and Sm isotopic anomalies in small (<20 ng Nd and Sm) sample sizes via thermal ionization mass spectrometer using 1013 Ω amplifiers. Ryugu samples exhibit resolvable negative μ142Nd values consistent with carbonaceous chondrite values, suggesting that Ryugu is related to the parent bodies of carbonaceous chondrites. Ryugu's negative μ149Sm values are the result of exposure to galactic cosmic rays, as demonstrated by the correlation between 150Sm/152Sm and 149Sm/152Sm ratios that fall along the expected neutron capture correlation line. The neutron fluence calculated in the "A" samples (2.75 ± 1.94 × 1015 n cm−2) is slightly higher compared to the "C" samples (0.95 ± 2.04 × 1015 n cm−2), though overlapping within measurement uncertainty. The Sm results for Ryugu, at this level of precision, thus are consistent with a well‐mixed surface layer at least to the depths from which the "A" and "C" samples derive. [ABSTRACT FROM AUTHOR]

The article provides a brief description of the Liulin-MO dosimeter, which is part of the FREND (Fine Resolution Epithermal Neutron Detector) device installed on the TGO (Trace Gas Orbiter) spacecraft of the ExoMars-2016 mission. Since April 2018, TGO has been operating in orbit around Mars. Data are presented on the radiation environment in the orbit of Mars during the decline phase of the 24th cycle of solar activity and the growth phase of the 25th cycle. During the period under review, a maximum flux and dose rate due to galactic cosmic rays (GCR) were observed. Between July 2021 and March 2023, the Liulin-MO dosimeter recorded eight increases in particle fluxes and dose rates from solar proton events (SPEs). Data are presented on the radiation environment during the SPE in Mars orbit in July 2021–March 2022, when Mars was on the opposite side of the Sun from Earth. A comparison is made of particle fluxes measured in orbits around the Earth and Mars. [ABSTRACT FROM AUTHOR]

Moon is an auspicious environment for the study of Galactic cosmic rays (GCR) and Solar Particle Events (SEP) due to the absence of magnetic field and atmosphere. The same characteristics raise the radiation risk for human presence in orbit around it or at the lunar surface. The secondary (albedo) radiation resulting from the interaction of the primary radiation with the lunar soil adds an extra risk factor, because neutrons are produced, but also it can be exploited to study the soil composition. In this paper, the design of a comprehensive radiation monitor package tailored to the lunar environment is presented. The detector, named LURAD, will perform spectroscopic measurements of protons, electrons, heavy ions, as well as gamma-rays, and neutrons. A microdosimetry monitor subsystem is foreseen which can provide measurements of LET(Si) spectra in a wide dynamic range of LET(Si) and flux for SPE and GCR, detection of neutrons and biological dose for radiation protection of astronauts. The LURAD design leverages on the following key enabling technologies: (a) Fully depleted Si monolithic active pixel sensors; (b) Scintillators read by silicon photomultipliers (SiPM); (c) Silicon on Insulator (SOI) microdosimetry sensors; These technologies promise miniaturization and mass reduction with state-of-the-art performance. The instrument's design is presented, and the Monte Carlo study of the feasibility of particle identification and kinetic energy determination is discussed. [ABSTRACT FROM AUTHOR]

High-voltage semiconductor devices are vulnerable to Single Event Burnout (SEB) as a result of interactions with Galactic Cosmic Rays (GCR). SEB is a permanent failure triggered by the passage of a single particle during the turn-off state of the device. This paper investigates SEB in a PiN diode induced by various ions in space through simulation. The Linear Energy Transfer (LET) of the ions studied was determined using SRIM. Additionally, the electrical properties of the device due to irradiation were analyzed using the Silvaco TCAD tool. The key indicator of SEB occurrence is the threshold voltage of SEB (VSEB). Therefore, the correlation between the ion's LET and VSEB was investigated. The results indicate that the most sensitive region is in the middle of the device, and SEB is caused by avalanche multiplication of ion-generated carriers. It was also observed that the VSEB decreased from 3200 V to 2100 V; as the LET increased from 0.19 to 58 MeV.cm².mg-1 for He and Ta, respectively. Consequently, ions with higher LET values can cause the device to burnout at a lower VSEB level, increasing the device’s sensitivity to SEB. [ABSTRACT FROM AUTHOR]

The heliosphere is full of galactic cosmic rays (GCR), high‐energy charged particles coming isotropically from the galaxy. The GCR interact with the solar wind blown by the Sun carrying out plasma, magnetic fields and transient structures such as interplanetary coronal mass ejections (ICMEs) and their associated magnetic flux ropes (MFR). The GCR interaction with ICMEs has been extensively studied particularly the GCR flux attenuation (known as Forbush decreases) as a result of interacting with the ICME sheath and magnetic field. In this work, we investigate the opposite effect: the MFR's ability to generate GCR anisotropies which an observer may detect as an increase in the GCR flux. To achieve this, we simulated a flux of protons with energies in the 10–160 GeV range arriving from all directions to a cylindrical MFR (with and without sheath) with plasma, magnetic field, and spatial dimensions found in average ICMEs observed at 1 au. By following the individual trajectories of the injected particles we found that the MFR deviates the charged particles preferentially in one direction parallel to the MFR–axis. We also found that the peak of this anisotropic GCR flux depends on: the angle between the MFR and ambient magnetic fields; the presence or not of the sheath region; the energy of the incident particles and the observer location inside the MFR. Key Points: We show that magnetic flux ropes associated to interplanetary coronal mass ejections produce anisotropies in the cosmic rays fluxThis finding helps to understand the anisotropies and enhancements of galactic cosmic rays (GCR) observed when magnetic clouds reaches the EarthOur numerical simulations can be extended to any scenery where cosmic rays interacts with magnetic flux ropes [ABSTRACT FROM AUTHOR]

Metformin is a biguanide currently used in the treatment of diabetes mellitus type 2. Besides its anti-glycemic effects, metformin has been reported to induce different cellular pleiotropic effects, depending on concentration and time of treatment. Here we report one administration of metformin (0.5 mM) has radioprotective effects in vitro on BJ human fibroblasts, increasing DNA damage repair and increasing SOD1 expression in the nucleus. Importantly, metformin (200 mg/kg) pre-administration for only 3 days in wild type 129/sv mice, decreases the formation of micronuclei in bone marrow cells and DNA damage in colon and lung tissues compared to control irradiated mice at sub-lethal and lethal doses, increasing the overall survival fraction by 37% after 10Gy total body irradiation. We next pre-treated with metformin and then exposed 129/sv mice, to a galactic cosmic rays simulation (GCRsim), at the NASA Space Radiation Laboratory (NSRL). We found metformin pre-treatment decreases the presence of bone marrow micronuclei and DNA damage in colon and lung tissues and an increase of 8-oxoguanine DNA glycosylase-1 (OGG1) expression. Our data highlight a radioprotective effect of metformin through an indirect modulation of the gene expression involved in the cellular detoxification rather than its effects on mitochondria. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Aims. Astrophysical ices on dust grain mantles in the interstellar medium (ISM) and dense circumstellar envelopes (CSEs) are continuously exposed to galactic cosmic rays (GCRs). In a laboratory setting, we studied the physical and chemical modifications of ice layers induced by energetic heavy ions as GCR analogues. The ice layers used have a molecular composition similar to that of icy grain mantles. Methods. Mixtures of H2O:CO:CH3OH molecules (percentages 73:24:3, 68:30:3, and 58:38:3) were condensed on a substrate at 15 K and irradiated with 40 MeV 58Ni11+ ion beams. Irradiation-induced modifications were followed using the mid-infrared absorption spectroscopy technique. Results. We observed the evolution of infrared bands of CO2, HCO, HCOOH, CH4, H2CO,H2O2, and more complex synthesised molecules. From the molecular column densities, cross-sections and sputtering yields were determined and compared to published results of water and carbon monoxide. Analysis of the chemical modifications reveals that the precursors are easily destroyed when they are in a molecular mixture, while others are desorbed. Conclusions. The main radiolitic modifications induced by GCR irradiations are molecular decomposition and sputtering. Extrapolation to astrophysical radiation conditions shows a strong dependence on the intensity of the GCR distributions at low energies, which allows the analysis of the ice evolution at timescales comparable to those of the ISM and CSE. [ABSTRACT FROM AUTHOR]

Space radiobiology, a multidisciplinary field investigating the biological effects of ionizing radiation on astronauts during space missions, plays a pivotal role in understanding and mitigating health risks associated with Galactic Cosmic Rays and solar radiation. The INFN Roma Sapienza Alpha Magnetic Spectrometer research group has been at the forefront of advancing research in this critical domain over the last five years. This presentation highlights the interdisciplinary approach employed in our research activities, emphasizing the collaborative efforts that have significantly contributed to the assessment of health risks induced by GCR radiation exposure. Our research endeavors delve into dose-effects models, establishing crucial relationships and providing a theoretical framework for modelling non-target effects resulting from space radiation—a paramount consideration in evaluating carcinogenic risks associated with deep space exploration. Furthermore, the discussion sheds light on the roles played by data collected from astroparticle experiments operating in space, with a specific focus on the mid and heavy nuclei components of space radiation. An integral aspect of our recent initiatives involves collaboration with esteemed research institutions, notably the National Institute for Laser, Plasma, and Radiation Physics (INFLPR) in Bucharest. This collaborative effort aims to explore the potential of reproducing space radiation conditions through ground experiments, employing innovative Laser Plasma Accelerators and the launch of a research topic collection dedicated to space radiobiology. This initiative further amplifies our commitment to advancing knowledge in this multidisciplinary field. [ABSTRACT FROM AUTHOR]

The variability of galactic cosmic rays near Earth is nearly isotropic and driven by large-scale heliospheric modulation but rarely can very local anisotropic events be observed in low-energy cosmic rays. These anisotropic cosmic-ray enhancement (ACRE) events are related to interplanetary transients. Until now, two such events have been known. Here, we report the discovery of the third ACRE event observed as an increase of up to 6.4% in count rates of high- and midlatitude neutron monitors between ca. 09 – 14 UT on 5 November 2023 followed by a moderate Forbush decrease and a strong geomagnetic storm. This is the first known observation of ACRE in the midrigidity range of up to 8 GV. The anisotropy axis of ACRE was in the nearly anti-Sun direction. Modeling of the geomagnetic conditions implies that the observed increase was not caused by a storm-induced weakening of the geomagnetic shielding. As suggested by a detailed analysis and qualitative modeling using the EUHFORIA model, the ACRE event was likely produced by the scattering of cosmic rays on an intense interplanetary flux rope propagating north of the Earth and causing a glancing encounter. The forthcoming Forbush decrease was caused by an interplanetary coronal mass ejection that hit Earth centrally. A comprehensive analysis of the ACRE and complex heliospheric conditions is presented. However, a full quantitative modeling of such a complex event is not possible even with the most advanced models and calls for further developments. [ABSTRACT FROM AUTHOR]

The Cygnus region, which contains massive molecular and atomic clouds and young stars, is a promising Galactic neutrino source candidate. Cosmic-ray transport in the region can produce neutrinos and γ -rays. Recently, the Large High Altitude Air Shower Observatory (LHAASO) detected an ultrahigh-energy γ -ray bubble (Cygnus Bubble) in this region. Using publicly available track events detected by the IceCube Neutrino Observatory in 7 yr of full detector operation, we conduct searches for correlated neutrino signals from the Cygnus Bubble with neutrino emission templates based on LHAASO γ -ray observations. No significant signals were found for any employed templates. With the 7 TeV γ -ray flux template, we set a flux upper limit of 90% confidence level for the neutrino emission from the Cygnus Bubble to be 5.7 × 10−13 TeV−1 cm−2 s−1 at 5 TeV. [ABSTRACT FROM AUTHOR]

Energetic positrons have been observed in the interstellar medium, and high-energy positrons with relativistic energies up to approximately 1 TeV have been detected in Galactic cosmic rays. We conducted a study on the acceleration of particles, specifically positrons, in a nonrelativistic quasi-parallel collisionless shock induced by a plasma consisting of protons, electrons, and positrons. The positron-to-proton number density ratio in the plasma is 0.1. We focused on a representative shock with a sonic Mach number of 17.1 and an Alfvénic Mach number of 16.8 in the rest frame of the shock. To investigate the acceleration mechanisms of particles including positrons in the shock, we utilized 1D particle-in-cell simulations. It was found that all three species of particles in the shock can be accelerated and exhibit power-law spectra. At the shock front, a significant portion of incoming upstream particles are reflected and undergo significant energy increases, and these reflected particles can be efficiently injected into the process of diffusive shock acceleration (DSA). Moveover, the reflected positrons can be further accelerated by an electric field parallel to the magnetic field when they move along the magnetic field upstream of the shock. As a result, positrons can be preferentially accelerated to be injected in the DSA process compared to electrons. [ABSTRACT FROM AUTHOR]

A new full model of the atmospheric transport of cosmogenic 10Be is presented based on the specialized SOCOL‐AERv2‐BE chemistry‐climate model coupled with the CRAC:10Be isotope production model. The model includes all the relevant atmospheric processes and allows computing the isotope concentration at any given location and time. The full model is directly compared with 10Be isotope measurements in five Antarctic and Greenland ice cores for the period 1980–2007. The model reasonably well reproduces the average concentration and solar‐cycle dependency or the lack of it for most observational sites but does not perfectly catch the interannual variability at sites with complex orography likely due to the coarse model grid. This implies that the model correctly reproduces the large‐scale atmospheric dynamics but effectively averages out synoptic‐scale variability. It is found that the dominant source of 10Be is located in the middle stratosphere (25–40 km), in the tropical (<30° latitudes) and polar (>60°) regions, as produced by galactic cosmic rays and solar energetic particles, respectively. It is shown that >60% (90%) of 10Be produced in the atmosphere reaches the Earth's surface within one (two) years, respectively. For practical purposes, a simple parameterization of the full‐model results is presented which agrees with the full model within 20% in polar regions. This parameterization allows one to make a quick estimate of near‐ground 10Be concentrations based only on production rates without heavy calculations. This practical approach can be applied to studies of solar and geomagnetic variability using cosmogenic isotopes. Key Points: A full model of production and atmospheric transport of 10Be produced by galactic cosmic ray (GCR) and solar energetic particles (SEP) is presented and validatedThe dominant source regions of 10Be in polar ice are identified as tropical and polar stratosphere for GCR and SEPs, respectivelyAn easy‐to‐use parameterization of the full model is proposed to study cosmic‐ray variability with 10Be data [ABSTRACT FROM AUTHOR]

The manifestation of extreme solar proton events (SPEs) in Beryllium‐10 (10Be) ice core data contains valuable information about the strength and incidence of SPEs or local characteristics of the atmosphere. To extract this information, the signals of enhanced production of cosmogenic 10Be due to the SPEs have to be detected, hence distinguished from the variability of the background production by galactic cosmic rays (GCRs). Here, we study the transport and deposition of 10Be from GCRs, using the ECHAM/MESSy Atmospheric Chemistry climate model, and discuss the detectability of extreme SPEs (similar to the CE 774/775 SPE) in 10Be ice core data depending on the ice core location, seasonal appearance of the SPE, atmospheric aerosol size distribution and phase of the 11‐year solar cycle. We find that sedimentation can be a major deposition mechanism of GCR generated 10Be, especially at high latitudes, depending on the aerosols to which 10Be attaches after production. The comparison of our results to four ice core records of 10Be from Greenland and Antarctica shows good agreement for both 10Be from GCRs and solar energetic particles (SEP). From our results we deduce that the location of detection and the season of occurrence of the SPE have a considerable effect on its detectability, as well as the aerosol size distribution the produced cosmogenic nuclides meet in the atmosphere. Furthermore, we find that SPEs occurring in the phase of highest activity during the 11‐year solar cycle are more detectable than SPEs that arise in the phase of lowest activity. Plain Language Summary: Solar proton events are eruptions of particles from the Sun that can cause an increased production of Beryllium‐10 in Earth's atmosphere. This increase can be detected in ice cores, which can tell us about the dynamics of the Sun or local characteristics of the atmosphere. To detect solar proton events in ice cores, the signal must be distinguished from the background production of Beryllium‐10 from galactic cosmic rays, because the two signals can be very similar. Here, we used a climate model to study the deposition of Beryllium‐10 from galactic cosmic rays and simulated the detectability of solar proton events in ice cores for different locations, months of occurrence, sizes of aerosols in the atmosphere, and phases of the 11‐year solar cycle. We found that sedimentation can be a major deposition mechanism for Beryllium‐10, especially at high latitudes. We also found that the season of the solar proton event has a big impact on its detectability. Furthermore, we show that solar proton events that occur during high solar activity are more easily detected than events that occur during a phase of low activity. The findings are useful to improve the interpretation of Beryllium‐10 ice core records. Key Points: The role of galactic cosmic rays for the detectability of solar proton events in Beryllium‐10 ice core records was studied in a 3D‐modelWe show that sedimentation can be a major deposition mechanism for Beryllium‐10, especially at high latitudesThe seasonal timing of the solar proton event and the phase of the 11‐year solar cycle during the event have an impact on its detectability [ABSTRACT FROM AUTHOR]

In orbital and ground-based experiments, it has been demonstrated that ionizing radiation (IR) can stimulate the locomotor and exploratory activity of rodents, but the underlying mechanism of this phenomenon remains undisclosed. Here, we studied the effect of combined IR (0.4 Gy γ-rays and 0.14 Gy carbon-12 nuclei) on the locomotor and exploratory activity of rats, and assessed the sensorimotor cortex volume by magnetic resonance imaging-based morphometry at 1 week and 7 months post-irradiation. The sensorimotor cortex tissues were processed to determine whether the behavioral and morphologic effects were associated with changes in neurotrophin content. The irradiated rats were characterized by increased locomotor and exploratory activity, as well as novelty-seeking behavior, at 3 days post-irradiation. At the same time, only unirradiated rats experienced a significant decrease in the sensorimotor cortex volume at 7 months. While there were no significant differences at 1 week, at 7 months, the irradiated rats were characterized by higher neurotrophin-3 and neurotrophin-4 content in the sensorimotor cortex. Thus, IR prevents the age-associated decrease in the sensorimotor cortex volume, which is associated with neurotrophic and neurogenic changes. Meanwhile, IR-induced increases in locomotor activity may be the cause of the observed changes. [ABSTRACT FROM AUTHOR]

Cosmic radiation exposure is one of the important health concerns for aircrews. In this work, we constructed a back propagation neural network model for the real-time and rapid assessment of cosmic radiation exposure to the public in aviation. The multi-dimensional dataset for this neural network was created from modeling the process of cosmic ray transportation in magnetic field by geomagnetic cutoff rigidity method and air shower simulation by a Monte Carlo based Geant4 code. The dataset was characterized by parameters including cosmic ray energy spectrum, K p-index, coordinated universal time, altitude, latitude, and longitude. The effective dose and dose rate was finally converted from the particle fluxes at flight position by the neural network. This work shows a good agreement with other models from International Civil Aviation Organization. It is also illustrated that the effective dose rate by galactic cosmic ray is <10 μSv h−1 and the value during ground level enhancement (GLE) 42 is 4 ~ 10 times larger on the routes calculated in this work. In GLE 69, the effective dose rate reaches several mSv h−1 in the polar region. Based on this model, a real-time warning system is achieved. [ABSTRACT FROM AUTHOR]

The Kuiper Belt object (KBO) Arrokoth, the farthest object in the Solar System ever visited by a spacecraft, possesses a distinctive reddish surface and is characterized by pronounced spectroscopic features associated with methanol. However, the fundamental processes by which methanol ices are converted into reddish, complex organic molecules on Arrokoth's surface have remained elusive. Here, we combine laboratory simulation experiments with a spectroscopic characterization of methanol ices exposed to proxies of galactic cosmic rays (GCRs). Our findings reveal that the surface exposure of methanol ices at 40 K can replicate the color slopes of Arrokoth. Sugars and their derivatives (acids, alcohols) with up to six carbon atoms, including glucose and ribose--fundamental building block of RNA--were ubiquitously identified. In addition, polycyclic aromatic hydrocarbons (PAHs) with up to six ring units (13C22H12) were also observed. These sugars and their derivatives along with PAHs connected by unsaturated linkers represent key molecules rationalizing the reddish appearance of Arrokoth. The formation of abundant sugar-related molecules dubs Arrokoth as a sugar world and provides a plausible abiotic preparation route for a key class of biorelevant molecules on the surface of KBOs prior to their delivery to prebiotic Earth. [ABSTRACT FROM AUTHOR]

Forbush effects in galactic cosmic rays (according to the neutron monitor network data) and accompanying geomagnetic disturbances over a long period from 1957 to 2022 have been identified and studied. Statistical relationships between various parameters of cosmic ray flux variations and geomagnetic activity indices are analyzed. It has been established that the magnitude of Forbush effects depends nonlinearly on the class of geomagnetic storm. A moderate correlation (up to 0.67) was found between the extreme values of various geomagnetic activity indices (Ap, Kp, Dst) and cosmic ray characteristics. It is shown that the extreme values of cosmic ray and geomagnetic activity parameters are not always detected simultaneously: it depends on the sign of the Bz-component of the interplanetary magnetic field in a specific event. [ABSTRACT FROM AUTHOR]

Galactic cosmic rays (GCRs) interact with the Earth's atmosphere to produce energetic neutrons and cosmogenic radionuclides, such as 14C. The atmosphere is partially shielded from the interstellar GCR spectrum by both the geomagnetic and solar magnetic fields. Solar shielding is often expressed as the heliospheric modulation potential ϕ , which consolidates information about the strength and structure of the solar magnetic field into a single parameter. For the period 1951 to today, ϕ can be estimated from ground-based neutron monitor data. Prior to 1950, 14C in tree rings can be used to estimate ϕ and hence the solar magnetic field, back centuries or millennia. Bridging the gap in the ϕ record is therefore of vital importance for long-term solar reconstructions. One method is to model ϕ using the sunspot number (SN) record. However, the SN record is only an indirect measure of the Sun's magnetic field, introducing uncertainty, and the record suffers from calibration issues. Here we present a new reconstruction of ϕ based on geomagnetic data, which spans both the entire duration of the neutron monitor record and stretches back to 1845, providing a significant overlap with the 14C data. We first modify and test the existing model of ϕ based on a number of heliospheric parameters, namely the open solar flux F S , the heliospheric current sheet tilt angle α , and the global heliospheric magnetic polarity p . This modified model is applied to recently updated geomagnetic estimates of F S and cyclic variations of α and p . This approach is shown to produce an annual estimate of ϕ in excellent agreement with that obtained from neutron monitors over 1951 – 2023. It also suggests that ionisation chamber estimates of ϕ – which have previously been used to extend the instrumental estimate back from 1951 to 1933 – are not well calibrated. Comparison of the new geomagnetic ϕ with 14C estimates of ϕ suggests that the long-term trend is overestimated in the most recent 14C data, possibly due to hemispheric differences in the Suess effect, related to the release of carbon by the burning of fossil fuels. We suggest that the new geomagnetic estimate of ϕ will provide an improved basis for future calibration of long-term solar activity reconstructions. [ABSTRACT FROM AUTHOR]

The research of the electron and positron spectrum of galactic cosmic rays is an important task of high-energy astrophysics. The necessity of using new methods of electron and positron registration is caused by insufficient statistical reliability of data from modern experiments in the TeV energy range. In the present work, one of the possible registration methods based on the use of synchrotron radiation of electrons and positrons in the Earth's magnetic field is investigated. Using modeling of trajectories of high-energy electrons, positrons, and synchrotrons photons emitted by them, the detector count rate for the ISS and ROS orbits has been estimated. The possibility of separation of electrons and positrons using this method is shown. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Enols—tautomers of ketones or aldehydes—are considered key intermediates in the formation of prebiotic sugars and sugar acids. Although laboratory simulation experiments suggest that enols should be ubiquitous in the interstellar medium, the underlying formation mechanisms of enols in interstellar environments are largely elusive. Here, we present the laboratory experiments on the formation of glyoxal (HCOCHO) along with its ynol tautomer acetylenediol (HOCCOH) in interstellar ice analogs composed of carbon monoxide (CO) and water (H2O) upon exposure to energetic electrons as a proxy for secondary electrons generated from Galactic cosmic rays. Utilizing tunable vacuum ultraviolet photoionization reflectron time-of-flight mass spectrometry, glyoxal and acetylenediol were detected in the gas phase during temperature-programmed desorption. Our results reveal the formation pathways of glyoxal via radical–radical recombination of two formyl (HĊO) radicals, and that of acetylenediol via keto-enol-ynol tautomerization. Due to the abundance of carbon monoxide and water in interstellar ices, glyoxal and acetylenediol are suitable candidates for future astronomical searches. Furthermore, the detection of acetylenediol in astrophysically relevant ices advances our understanding for the formation pathways of high-energy tautomers such as enols in deep space. [ABSTRACT FROM AUTHOR]

A mini‐neutron monitor (MNM) was installed at the German Antarctic Neumayer III station, measuring the variation of galactic cosmic rays and searching for Forbush Decreases (FDs) caused by solar activities. Running continuously from 2014 until the end of 2017, the long‐term stability of the detector could be investigated. After correcting the air pressure and normalization to the 27 days running mean averages of the SANAE and TERA Neutron Monitors (NMs), the daily running mean count rates are compared with the SANAE and TERA NMs also installed in Antarctica. For most of the 14 FDs with magnitudes greater than 3, taken from the list compiled by the IZMIRAN group (http://spaceweather.izmiran.ru/eng/dbs.html), the three detectors show consistent particle flux variation, although the average rate of the MNM is more than a hundred times smaller. The light and low‐cost MNM is an ideal alternative to heavy and old NMs, especially at high altitudes and remote environments. Plain Language Summary: A mini‐neutron monitor (MNM) was installed at the German Antarctic Neumayer III station from 2014 till the end of 2017, measuring the variation of galactic cosmic rays and investigating its sensitivity by searching for Forbush decreases (FDs). The data were successfully corrected for pressure and normalized to the long‐term trend utilizing 27‐day running mean averages of the weighted mean of SANAE and TERA NMs. A comparison with the SANAE and Terre Adelie NMs on the basis of daily running mean averages reveals a difference of about 1% for each combination. Utilizing the IZMIRAN FD catalog, we showed that the sensitivity of the MNM is large enough to investigate FDs with amplitudes above 3%, making the MNM a useful instrument for space weather investigations. Key Points: Measurements of Galactic Cosmic Rays by a mini‐neutron monitor (MNM) at the German Antarctic Research Station from 2014 to 2017 are presentedThe measurements were successfully corrected for pressure and normalized to the weighted mean of the SANAE and TERA Neutron MonitorWe show that Forbush Decreases with amplitudes above 3% in Magnitude identified by the IZMIRAN database can be identified with the MNM too [ABSTRACT FROM AUTHOR]

For missions beyond low Earth orbit to the moon or Mars, space explorers will encounter a complex radiation field composed of various ion species with a broad range of energies. Such missions pose significant radiation protection challenges that need to be solved in order to minimize exposures and associated health risks. An innovative galactic cosmic ray simulator (GCRsim) was recently developed at the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory (BNL). The GCRsim technology is intended to represent major components of the space radiation environment in a ground analog laboratory setting where it can be used to improve understanding of biological risks and serve as a testbed for countermeasure development and validation. The current GCRsim consists of 33 energetic ion beams that collectively simulate the primary and secondary GCR field encountered by humans in space over the broad range of particle types, energies, and linear energy transfer (LET) of interest to health effects. A virtual workshop was held in December 2020 to assess the status of the NASA baseline GCRsim. Workshop attendees examined various aspects of simulator design, with a particular emphasis on beam selection strategies. Experimental results, modeling approaches, areas of consensus, and questions of concern were also discussed in detail. This report includes a summary of the GCRsim workshop and a description of the current status of the GCRsim. This information is important for future advancements and applications in space radiobiology.