High Energetic Particles Research Articles

Very High Energy Solar Energetic Particle Events and Ground Level Enhancement Events: Forecasting and Alerts

AbstractA Ground Level Enhancement (GLE) event can be observed as an increase in the background of ground‐based neutron monitor observations and is often associated with an increase of >500 MeV space‐based proton flux measurements. GLE events begin as very high‐energy SEP events associated with GeV protons. For such events to be detected at sea level, proton energies must exceed about 433 MeV. Since the increased flux of such particles can be a major problem to technology in space and on Earth and pose a threat for human health, developing real time warning systems is of great importance. GLE Alert++ is a product, built by the Athens Cosmic Ray Group of the National and Kapodistrian University of Athens, that issues alerts when a GLE event starts to register and is based on ground‐based neutron monitor observations. From the space‐based approach, the HESPERIA UMASEP‐500 product, jointly developed within the framework of the EU HORIZON2020 HESPERIA project by the Universidad de Malaga, Spain and National Observatory of Athens, Greece, provides forecasts of GLE events and >500 MeV protons relying on GOES satellite Soft X‐Ray and high energy proton observations. These two products are fully integrated as federated products on the ESA SWE Portal and are provided as part of the ESA Space Safety Program Space Weather Service Network. In this paper we present how the products were built, provide examples of their outputs as seen on the ESA SWE Portal, and show how the products complement each other and how using them together can in some instances provide more information for users of these services.

An Assessment of the GLE Alert++ Warning System

Over the last years the Athens Cosmic Ray Group of the National & Kapodistrian University of Athens has implemented a warning tool called GLE Alert, which is a highly credible application that issues alerts when a ground level enhancement (GLE) starts due to very high energy solar energetic particles reaching the Earth. This application warns of a high intensity solar energetic particle event up to several minutes before it reaches near the near-Earth space environment. In this work, an assessment of the latest updated version of GLE Alert, GLE Alert++, is presented. GLE Alert++ is a federated product of the ESA S2P SWE Space Radiation Expert Service Centre, which is part of the ESA Space WEather Service NETwork (SWESNET) project. The assessment of the GLE Alert++, which was finalized in October 2022, focused on: (a) the availability of the real-time data provided by the neutron monitor stations that contribute to the GLE Alert++, (b) the behaviour of each station regarding the different Alert levels status (Watch, Warning and Alert), and (c) the definition of the real-time assessment index. The results of this work are of essential importance since they ensure a reliable and trustworthy warning tool, and can be highly useful in protecting humans during extreme solar energetic events.

Relativistic electron beams accelerated by an interplanetary shock

Context. Collisionless shock waves have long been considered to be among the most prolific particle accelerators in the universe. Shocks alter the plasma they propagate through, and often exhibit complex evolution across multiple scales. Interplanetary (IP) traveling shocks have been recorded in situ for over half a century and act as a natural laboratory for experimentally verifying various aspects of large-scale collisionless shocks. A fundamentally interesting problem in both heliophysics and astrophysics is the acceleration of electrons to relativistic energies (> 300 keV) by traveling shocks. Aims. The reason for an incomplete understanding of electron acceleration at IP shocks is due to scale-related challenges and a lack of instrumental capabilities. This Letter presents the first observations of field-aligned beams of relativistic electrons upstream of an IP shock, observed thanks to the instrumental capabilities of Solar Orbiter. This study presents the characteristics of the electron beams close to the source and contributes to the understanding of their acceleration mechanism. Methods. On 25 July 2022, Solar Orbiter encountered an IP shock at 0.98 AU. The shock was associated with an energetic storm particle event, which also featured upstream field-aligned relativistic electron beams observed 14 min prior to the actual shock crossing. The distance of the beam’s origin was investigated using a velocity dispersion analysis (VDA). Peak-intensity energy spectra were anaylzed and compared with those obtained from a semi-analytical fast-Fermi acceleration model. Results. By leveraging Solar Orbiter’s high temporal resolution Energetic Particle Detector (EPD), we successfully showcase an IP shock’s ability to accelerate relativistic electron beams. Our proposed acceleration mechanism offers an explanation for the observed electron beam and its characteristics, while we also explore the potential contributions of more complex mechanisms.

Mildly Relativistic Perpendicular Multiple-ion GRB Shocks

Mildly relativistic perpendicular, collisionless multiple-ion gamma-ray burst shocks are analyzed using 2D3V particle-in-cell simulations. A characteristic feature of multiple-ion shocks is alternating maxima of the α particle and the proton densities, at least in the early downstream. Turbulence, shock-drift acceleration, and evidence of stochastic acceleration are observed. We performed simulations with both in-plane (B y ) and out-of-plane (B z ) magnetic fields, as well as in a perpendicular shock setup with φ = 45°, and saw multiple differences: while with B z , the highest-energetic particles mostly gain energy at the beginning of the shock, with B y , particles continue gaining energy and it does not appear that they have reached their final energy level. A larger magnetization σ leads to more high-energetic particles in our simulations. One important quantity for astronomers is the electron acceleration efficiency ϵ e , which is measurable due to synchrotron radiation. This quantity hardly changes when changing the amount of α particles while keeping σ constant. It is, however, noteworthy that ϵ e strongly differs for in-plane and out-of-plane magnetic fields. When looking at the proton and α acceleration efficiency, ϵ p and ϵ α , the energy of α particles always decreases when passing the shock into the downstream, whereas the energy of protons can increase if α particles account for the majority of the ions.

Development and application of a hybrid MHD-kinetic model in JOREK

Energetic particle (EP)-driven instabilities will be of strongly increased relevance in future burning plasmas as the EP pressure will be very large compared to the thermal plasma pressure. Understanding the interaction of EPs and bulk plasma is crucial for developing next-generation fusion devices. In this work, the JOREK magnetohydrodynamic code and its full-f kinetic particle-in-cell module are extended by an anisotropic pressure coupling model to allow for the simulation of EP instabilities at high EP pressures using realistic plasma and EP parameters. Furthermore, a diagnostic is implemented to allow for the visualization of phase-space resonances. The resulting code is first benchmarked linearly for the International Tokamak Physics Activity-toroidal Alfvén eigenmodes as well as the experiment-based ASDEX-Upgrade-NonLinear Energetic particle Dynamics cases, obtaining good agreement with other codes. Then, it is applied to a high energetic particle pressure discharge in the ASDEX Upgrade tokamak using a realistic non-Maxwellian distribution of EPs, reproducing aspects of the experimentally observed instabilities. Non-linear applications are possible based on the implementation, but will require dedicated verification and validation left for future work.

The Interstellar and Circumgalactic Media at low and high redshift as traced by Atomic Carbon and Carbon Monoxide

A different chemistry of the interstellar medium (ISM) is expected in the circumgalactic medium (CGM) gas where high-energetic particles (i.e. cosmic rays) seem to be produced in-situ by the hot X-ray gas, as it is observed in the Perseus cluster. This very different astrochemistry, where extreme gas-dust thermal decoupling is expected, and where CO can be destroyed over large massscales, is the subject of the investigation briefly reported here. We introduce an on-going project aiming at studying the properties of the CGM of two clusters at low and high redshift using their molecular gas tracers and thermal emission from dust.

Morphology of supernova remnants and their halos

Context. Supernova remnants (SNRs) are known to accelerate particles to relativistic energies, on account of their nonthermal emission. The observational progress from radio to gamma-ray observations reveals more and more morphological features that need to be accounted for when modeling the emission from those objects. Aims. We use our time-dependent acceleration code RATPaC to study the formation of extended gamma-ray halos around supernova remnants and the morphological implications that arise when the high-energetic particles start to escape from the remnant. Methods. We performed spherically symmetric 1D simulations in which we simultaneously solved the transport equations for cosmic rays, magnetic turbulence, and the hydrodynamical flow of the thermal plasma in a volume large enough to keep all cosmic rays in the simulation. The transport equations for cosmic rays and magnetic turbulence were coupled via the cosmic-ray gradient and the spatial diffusion coefficient of the cosmic rays, while the cosmic-ray feedback onto the shock structure can be ignored. Our simulations span 25 000 yr, thus covering the free-expansion and the Sedov-Taylor phase of the remnant’s evolution. Results. We find a strong difference in the morphology of the gamma-ray emission from supernova remnants at later stages dependent on the emission process. At early times, both the inverse-Compton and the Pion-decay morphology are shell-like. However, as soon as the maximum-energy of the freshly accelerated particles starts to fall, the inverse-Compton morphology starts to become center-filled, whereas the Pion-decay morphology keeps its shell-like structure. Escaping high-energy electrons start to form an emission halo around the remnant at this time. There are good prospects for detecting this spectrally hard emission with the future Cerenkov Telescope Array, as there are for detecting variations in the gamma-ray spectral index across the interior of the remnant. Further, we find a constantly decreasing nonthermal X-ray flux that makes a detection of X-ray unlikely after the first few thousand years of the remnants’ evolution. The radio flux is increasing throughout the SNR’s lifetime and changes from a shell-like to a more center-filled morphology later on.

Composition variations of major lunar elements: Possible impacts on lunar albedo spectra

Understanding the elemental composition of the lunar regolith is important for expanding our knowledge of the history and geology of the Moon. Several methods have already been used to achieve this purpose, including direct analysis of lunar samples and satellite spectroscopy. Since computer modeling is important for processing the collected data, and for the preparation of future missions, this work uses Monte Carlo simulations to study the radiation emitted by the lunar surface, via nuclear interactions between the incident radiation environment and lunar regolith, to characterize the elemental composition of the Moon. When high energy primary galactic cosmic rays and solar energetic particles strike the lunar surface, they either scatter to free space or produce secondaries through cascades of interactions, some of which escape the lunar surface. Both the scattered primaries and escaping secondaries constitute the lunar “albedo” particles studied in this paper. The purpose of this work is to determine whether enhancing the abundances of any of the major lunar elements (O, Na, Mg, Al, Si, Ca, Ti, Mn, and Fe) causes an observable difference in the spectra of albedo particles emitted by the regolith. The model-based results herein show that charged albedo particles do not display any significant differences for any element. They also confirm that low-energy neutrons and gamma rays produce observable variations with different lunar compositions. This provides evidence that albedo neutrons and/or gamma rays, and not protons, are the source of the variations observed in a recent map of the lunar albedo, generated by the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) instrument.

Gyrokinetic investigation of the nonlinear interaction of Alfvén instabilities and energetic particle-driven geodesic acoustic modes

This paper presents a study of the interaction between Alfvén modes and zonal structures, considering a realistic ASDEX Upgrade equilibrium. The results of gyrokinetic simulations with the global, electromagnetic, particle-in-cell code ORB5 are presented, where the modes are driven unstable by energetic particles with a bump-on-tail equilibrium distribution function, with radial density gradient. Two regimes have been observed. At low energetic particle concentration, the zonal structure (identified as an energetic particle-driven geodesic acoustic mode) is more unstable than the Alfvén mode. In the regime at high energetic particle concentration, the Alfvén mode is more unstable than the zonal structure. The interplay between the modes leads to a modification of their growth rates as well as to a modification of their saturation levels. The theoretical explanation of the mode interaction is given in terms of three-wave coupling of the energetic particle-driven geodesic acoustic mode and Alfvén mode, mediated by the curvature–pressure coupling term of the energetic particles.

THE SIMULATION OF VIBRATIONAL POPULATIONS OF ELECTRONICALLY EXCITED N2 IN TITAN’S UPPER ATMOSPHERE DURING PRECIPITATIONS OF HIGH-ENERGETIC PARTICLES

We study the electronic kinetics of singlet molecular nitrogen in Titan’s upper atmosphere during precipitations of high-energetic particles. Both radiative processes and processes of electron excitation energy transfer during inelastic collisions with N2 and CH4 molecules were considered in the calculation of vibrational populations of electronically excited singlet states a'1Σu–, a1Πg, w1Δu of molecular nitrogen in the upper atmosphere of Titan. It is shown that the calculated volume emission intensities of the Lyman-Birge-Hopfield bands correlate with the profiles of the ion production rate in the atmosphere of Titan during the considered cases of electron precipitation for considered interval of the energies 30-1000 eV of magnetospheric electrons. This fact is explained by the negligible contribution of collisional processes to the vibrational populations a1Πg(v'=0-6) in the considered range of heights above 900 km.

Analytic investigation of combined effects of anisotropic thermal transport and energetic particles on stability of resistive plasma resistive wall mode

The combined effects of anisotropic thermal transport and trapped energetic particles (EPs) on the stability of the resistive plasma resistive wall mode (RPRWM) are investigated by an energy-principle based analytical model. The results qualitatively confirm that of a recent toroidal modeling study [Bai et al., Phys. Plasmas 27, 072502 (2020)], in which the thermal transport can stabilize the RPPWM depending on the parameters of both the plasma equilibrium and energetic particles. The analytical model predicts a complete stabilization of the RPRWM in highly resistive plasmas, at sufficiently high EPs' pressure, and finite plasma flow. The stabilizing effect of thermal transport originates from its enhancement of energy dissipations associated with both the resistive layer and the trapped energetic particles.

Searching for boosted dark matter mediated by a new gauge boson

We study the possibility to directly detect the boosted dark matter generated from the scatterings with high energetic cosmic particles such as protons and electrons. As a concrete example, we consider the sub-GeV dark matter mediated by a $U(1)_D$ gauge boson which has mixing with $U(1)_Y$ gauge boson in the standard model. The enhanced kinetic energy of the light dark matter from the collision with the cosmic rays can recoil the target nucleus and electron in the underground direct detection experiments transferring enough energy to them to be detectable. We show the impact of BDM with existing direct detection experiments as well as collider and beam-dump experiments.

Verification of Energetic-Particle-Induced Geodesic Acoustic Mode in Gyrokinetic Particle SimulationsSupported by the National MCF Energy R&D Program (Grant Nos. 2018YFE0304100, 2018YFE0311300 and 2017YFE0301300), the National Natural Science Foundation of China (Grant Nos. 11675256, 11675257, 11835016, 11875067 and 11705275), the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB16010300), the Key Research Program of Frontier Science of

The energetic-particle-induced geodesic acoustic mode (EGAM) is studied using gyrokinetic particle simulations in tokamak plasmas. In our simulations, exponentially growing EGAMs are excited by energetic particles with a slowing-down distribution. The frequencies of EGAMs are always below the frequencies of GAMs, which is due to the non-perturbative contribution of energetic particles (EPs). The mode structures of EGAMs are similar to the corresponding mode structures of GAMs. Our gyrokinetic simulations show that a high EP density can enhance the EGAM growth rate, due to high EP free energy, and that EPs' temperature and the pitch angle of the distribution modify the EGAM frequency/growth rate by means of the resonance condition. Kinetic effects of the thermal electrons barely change the EGAM frequency, and have a weak damping effect on the EGAM. Benchmarks between the gyrokinetic particle simulations and a local EGAM dispersion relation exhibit good agreement in terms of EGAM frequency and growth rate.

Study of ionospheric scintillation during geomagnetic storms at equatorial anomaly region Bhopal

GPS L-band signals get affected by ionospheric scintillation; as a result, satellite navigation too gets affected. The most extreme scintillation activity is expected to occur near the equatorial region during geomagnetic storms. The behavior and morphology of low-latitude ionosphere are different from the other latitudes. The space weather conditions in low latitude show different nature because of the geomagnetic field. Due to penetration of soft, high energetic particles, the plasma density increases, which is the main source of generation of ionospheric irregularities scintillation. GPS scintillation at low latitudes is primarily associated with equatorial spread F. Equatorial spread F is caused by ionospheric irregularities with a spatial spectrum extending from 100 km to less than 1 m. When GPS signals encounter the ionospheric irregularities of various sizes produced during high geomagnetic and solar activity, they undergo drastic changes in their phase and amplitude scintillation indices. The accuracy and reliability of GPS system get affected by scintillation. Also the atmosphere air molecule’s content and deviation of electrons, protons, neutrons according to flow rate are observed. In the present paper, we have studied the scintillation activity at low-latitude station Bhopal.

Design and performance studies of the calorimeter system for a FCC-hh experiment

The physics reach and feasibility of the Future Circular Collider (FCC) with centre of mass energies up to 100 TeV and unprecedented luminosity has delivered a Conceptual Design Report early 2019. 100 TeV proton-proton collisions will produce very high energetic particle showers in the calorimeters from both, jets and composite objects such as boosted bosons/tops. The reconstruction of such objects sets the calorimeter performance requirements in terms of shower containment, energy resolution and granularity. Furthermore, high-precision measurements of photons and electrons over a wide energy range are crucial to fully exploit the FCC-hh physics potential, especially given the large amount of collisions per bunch crossing the detectors will have to face (pile-up of 0⟨ μ ⟩=100). The current reference technologies for the calorimeter system of the FCC-hh detector are presented: Liquid Argon (LAr) as the active material in the electromagnetic calorimeters, and the hadronic calorimeters for |η|>1.3 (Endcap and Forward region), and a Scintillator-Steel (Tile) calorimeter as hadronic calorimeter in the Barrel region. The paper will focus on the performance studies for single particles and jets in the combined calorimeter system. We will introduce the simulation framework and the reconstruction chain, that includes the calibration and clustering of calorimeter cells and the estimation of the electronics as well as the pile-up induced noise. In conclusion, the achieved performances will be compared to the physics benchmarks of the FCC-hh experiment.

Thermoluminescence response of detonation diamond microparticles exposed to beta and alpha radiation

The thermoluminescence (TL) dosimetric response observed in crystalline synthetic diamondspecimens of different origin has indicated excellent levels of performance as detector and dosimeter concerning high energetic photons and particle beams. In the present work, we report on the photoluminescence and TL characteristics of detonation diamond microcrystals having 250–300 μm grain size. The high quality of detonation diamond specimens was demonstrated by photoluminescence spectroscopy with 488 nm wavelength excitation, depicting clearly the presence of negative nitrogen-vacancy [NV]− and the neutral nitrogen-vacancy [NV]o center population localized at 1.946 eV and 2.157 eV, respectively as well as a vacancy trapped at dinitrogen (2.47 eV). The TL glow curve shape, repeatability, and thermal fading were studied in samples exposed to alpha and beta irradiation. A linear dose-response was observed in the ranges of 6.6–33 Gy and 13–33 Gy, for alpha and beta irradiations, respectively. The repeatability was determined to be about 2%. The detonation microdiamonds exhibited a TL thermal fading decay of around 50% TL in a 24 h after irradiation at room temperature. A computer glow curve deconvolution was utilized by assuming four mixed order kinetics overlapped TL peaks to determine their kinetic parameters. The TL glow curve shapes and the kinetics values of the TL peaks were comparable irrespective of alpha or beta irradiated samples. The findings reflect that detonation diamond microparticles are suitable material to be used as alpha and beta radiation TL dosimeters.

On the radar frequency dependence of polar mesosphere summer echoes

Polar mesosphere summer echoes (PMSEs) are very strong radar echoes in the polar mesopause in local summer. Here we present the frequency dependence of the volume reflectivity and the effect of energetic particle precipitation on modulated PMSEs by using PMSEs observations carried out by European Incoherent SCATter (EISCAT) heating equipment simultaneously with very high frequency (VHF) radar and ultra high frequency (UHF) radar on 12 July 2007. According to the experimental observations, the PMSEs occurrence rate at VHF was much higher than that at UHF, and the altitude of the PMSEs maximum observed at VHF was higher than that at UHF. Overlapping regions were observed by VHF radar between high energetic particle precipitation and the PMSEs. In addition, high-frequency heating had a very limited impact on PMSEs when the UHF electron density was enhanced because of energetic particle precipitation. In addition, an updated qualitative method was used to study the relationship between volume reflectivity and frequency. The volume reflectivity was found to be inversely proportional to the fourth power of radar frequency. The theoretical and experimental results provide a definitive data foundation for further analysis and investigation of the physical mechanism of PMSEs.

NVRH-LUT: A nonvolatile radiation-hardened hybrid MTJ/CMOS-basedlook-up table for ultralow power and highly reliable FPGA designs

Complementary metal oxide semiconductor (CMOS) downscaling leads to various challenges, such as high leakage current and increase in radiation sensitivity. To solve such challenges, hybrid MTJ/CMOS technology-based design has been considered as a very promising approach thanks to the high speed, low power, good scalability, and full compatibility of magnetic tunnel junction (MTJ) devices with CMOS technology. One important application of MTJs is the efficient utilization in building nonvolatile look-up tables (NV-LUTs) used in reconfigurable logic. However, NV-LUTs face severe reliability issues in nanotechnology due to the increasing process variations, reduced supply voltage, and high energetic particle strike at sensitive nodes of CMOS circuits. This paper proposes a nonvolatile radiation-hardened look-up table (NVRH-LUT) for advanced reconfigurable logic. Compared with previous works, the proposed NVRH-LUT is fully robust against single-event upsets and also single-event double-node upsets that are among the main reliability-challenging issues for NV-LUTs. Results have shown that NVRH-LUT not only provides increasing reliability and reduced bit error rate but also offers low delay and low energy consumption.

The effect of the particle surface and binder properties on the response of polymer bonded explosives at low impact velocities

Polymer bonded explosives are designed to initiate under controlled conditions. However, accidental ignition leading to a deflagration, and even detonation, may occur during manufacturing, handling and transport. Understanding how ignition depends on microstructural features, such as cracks and voids in the particles, and on the adhesive and mechanical properties of the binder through predictive numerical simulations and modeling will help to improve safety. Finite element simulations and experiments of a single high energetic material particle embedded in polymer binders are performed to investigate the effect of the material properties of the binder and the particle surface properties, on damage and temperature at an impact velocity of 10 m/s. Particles with low and high quality surface properties, and two different binders are analyzed. The simulations with the lower stiffness binder do not show a significant increase in temperature after impact. A polymer with higher stiffness induces more particle damage under impact contributing to a larger temperature rise. Furthermore, high quality surface and higher adhesion strength induces larger stresses and increase the temperature rise.

Radiation-Induced Helium Bubbles in Metals.

Helium (He) bubbles are typical radiation defects in structural materials in nuclear reactors after high dose energetic particle irradiation. In the past decades, extensive studies have been conducted to explore the dynamic evolution of He bubbles under various conditions and to investigate He-induced hardening and embrittlement. In this review, we summarize the current understanding of the behavior of He bubbles in metals; overview the mechanisms of He bubble nucleation, growth, and coarsening; introduce the latest methods of He control by using interfaces in nanocrystalline metals and metallic multilayers; analyze the effects of He bubbles on strength and ductility of metals; and point out some remaining questions related to He bubbles that are crucial for design of advanced radiation-tolerant materials.