Interaction Of Energetic Particles Research Articles

Asynchronous propagation of atomic force and excited electronic charge in GaAs under proton irradiation

The studies for the interaction of energetic particles with matter have greatly contributed to the exploration of material properties under irradiation conditions, such as nuclear safety, medical physics and aerospace applications. In this work, we theoretically simulate the non-adiabatic process for GaAs upon proton irradiation using time-dependent density functional theory, and find that the radial propagation of force on atoms and the excitation of electron in GaAs are non-synchronous process. We calculated the electronic stopping power on proton with the velocity of 0.1–0.6 a.u., agreement with the previous empirical results. After further analyzing the force on atoms and the population of excited electrons, we find that under proton irradiation, the electrons around the host atoms at different distances from the proton trajectories are excited almost simultaneously, especially those regions with relatively high charge density. However, the distant atoms have a significant hysteresis in force, which occurs after the surrounding electrons are excited. In addition, hysteresis in force and electron excitation behavior at different positions are closely related to the velocity of proton. This non-synchronous propagation reveals the microscopic dynamic mechanism of energy deposition into the target material under ion irradiation.

Threshold displacement energies and primary radiation damage in AlN from molecular dynamics simulations

Aluminum nitride (AlN) is an attractive material for sensing application in radiation environments owing to its radiation resistance, optical wide-bandgap, and piezoelectric properties. Yet, the variations of its physical properties under exposure to energetic particle needs to be better understood. Here, we report the results of the molecular dynamics simulations of the structural changes in AlN under irradiation via the knock-on atom technique. By creating and evolving irradiation cascades due to energetic particle interactions with the atoms of the crystalline lattice, we determine the rate of defect production as a function of the deposited energy. Further, we determine the threshold displacement energy, a key characteristic that describes how efficient the defect production in the given material is. We find that displacement threshold is slightly greater than isostructural gallium nitride and is lower than metal oxides used in radiation environments.

Nonlinear interaction of Alfvénic instabilities and turbulence via the modification of the equilibrium profiles

Nonlinear simulations of Alfvén modes (AMs) driven by energetic particles (EPs) in the presence of turbulence are performed with the gyrokinetic particle-in-cell code ORB5. The AMs carry a heat flux, and consequently they nonlinearly modify the plasma temperature profiles. The isolated effect of this modification on the dynamics of turbulence is studied by means of electrostatic simulations. We find that turbulence is reduced when the profiles relaxed by the AM are used, with respect to the simulation where the unperturbed profiles are used. This is an example of indirect interaction of EPs and turbulence. First, an analytic magnetic equilibrium with circular concentric flux surfaces is considered as a simplified example for this study. Then, an application to an experimentally relevant case of ASDEX Upgrade is discussed.

Nuclear data for space exploration

Understanding the harmful effects of galactic cosmic rays (GCRs) on space exploration requires a substantial amount of nuclear data. Specifically, the interaction of energetic GCR charged particles with spacecraft materials generates secondary radiations that, through energy deposition, can harm astronauts and electronic systems. By identifying the gaps in our knowledge of the relevant nuclear data—such as interaction cross sections—and identifying ways to fill those gaps—with measurements, compilations, evaluations, dissemination, reaction modeling, sensitivity studies, and uncertainty quantification—the safety and viability of space exploration can be improved. This work surveys the state of the art in this interdisciplinary field and identifies promising collaborative research topics that have significant potential to advance our understanding of the effects of the space radiation environment on space exploration.

Anomalous Transport of Energetic Particles Interacting with Dynamic Small-Scale Magnetic Flux Rope Structures

le Roux and Zank [25] showed previously how one can derive from first principles a pitch-angle dependent fractional diffusion-advection kinetic equation to model the anomalous diffusion of energetic particles interacting with small-scale magnetic flux ropes (SMFRs) in the inner heliosphere on the basis of the standard focused transport equation. This equation has the following limitations: (1) The asymptotic power law of a Lévy distribution was specified to model the non-Gaussian statistics of the disturbed energetic particle trajectories generated during energetic particle interaction with numerous SMFRs. The second moment (variance) and higher moments of the Lévy distribution are infinite, indicating over-efficient non-local transport that is scale-free. (2) The theory does not naturally allow for a transition of anomalous transport to normal diffusion, or to a different anomalous diffusion state. An outline of a derivation is presented in which an exponentially truncated Lévy distribution was specified instead, resulting in a tempered fractional diffusion-advection kinetic equation that addresses these two concerns.

A nonlinear model of diffusive particle acceleration at a planar shock

We study the process of nonlinear shock acceleration based on a nonlinear diffusion–advection equation. The nonlinearity is introduced via a dependence of the spatial diffusion coefficient on the distribution function of accelerating particles. This dependence reflects the interaction of energetic particles with self-generated waves. After thoroughly testing the grid-based numerical setup with a well-known analytical solution for linear shock acceleration at a specific shock transition, we consider different nonlinear scenarios, assess the influence of various parameters, and discuss the differences of the solutions to those of the linear case. We focus on the following observable features of the acceleration process, for which we quantify the differences in the linear and nonlinear cases: (1) the shape of the momentum spectra of the accelerated particles, (2) the time evolution of the solutions, and (3) the spatial number density profiles.

Investigating Particle Acceleration by Dynamic Small-scale Flux Ropes behind Interplanetary Shocks in the Inner Heliosphere

We recently extended our Parker-type transport equation for energetic particle interaction with numerous dynamic small-scale magnetic flux ropes (SMFRs) to include perpendicular diffusion in addition to parallel diffusion. We present a new analytical solution to this equation assuming heliocentric spherical geometry with spherical symmetry for all SMFR acceleration mechanisms present in the transport theory. With the goal of identifying the dominant mechanism(s) through which particles are accelerated by SMFRs, a search was launched to identify events behind interplanetary shocks that could be explained by our new solution and not classical diffusive shock acceleration. Two new SMFR acceleration events were identified in situ for the first time within heliocentric distances of 1 astronomical unit (au) in Helios A data. A Metropolis–Hastings algorithm is employed to fit the new solution to the energetic proton fluxes so that the relative strength of the transport coefficients associated with each SMFR acceleration mechanism can be determined. We conclude that the second-order Fermi mechanism for particle acceleration by SMFRs is more important than first-order Fermi acceleration due to the mean compression of the SMFRs regions during these new events. Furthermore, with the aid of SMFR parameters determined via the Grad–Shafranov reconstruction method, we find that second-order Fermi SMFR acceleration is dominated by the turbulent motional electric field parallel to the guide/background field. Finally, successful reproduction of energetic proton flux data during these SMFR acceleration events also required efficient particle escape from the SMFR acceleration regions.

Global Map of Chorus Wave Sizes in the Inner Magnetosphere

AbstractThe dynamics of the radiation belts are largely affected by the resonant interactions of energetic particles with plasma waves, such as whistler mode chorus waves. These waves play a direct and crucial role in the acceleration and loss of radiation belt electrons. The properties of these waves have been investigated thoroughly using various missions that carried wave instruments within the inner magnetosphere. One of the most conspicuous properties of chorus waves is the size of the wave packets. Past studies have estimated the size of chorus wave packets as a function of radial distance, magnetic latitude, and geomagnetic activity. This study takes advantage of the comprehensive wave data from the Van Allen Probes mission to draw a global map of the size of chorus wave packets in the inner magnetosphere. Results show that the size of lower band chorus wave packets varies between ∼1,000 and2,000 km depending on the intensity and activity of chorus waves in the inner magnetosphere. In general, the largest chorus wave packets are observed on the dawn‐dayside where chorus wave activity is also high. The results will help us better understand the interaction region and the generation mechanism of the chorus waves.

Flaremodel: An open-source Python package for one-zone numerical modelling of synchrotron sources

Synchrotron processes, the radiative processes associated with the interaction of energetic charged particles with magnetic field, are of interest in many areas in astronomy, from the interstellar medium to extreme environments near compact objects. Consequently, observations of synchrotron sources carry information on the physical properties of the sources themselves and those of their close vicinity. In recent years, novel observations of such sources with multi-wavelength collaborations reveal complex features and peculiarities, especially near black holes. Exploring the nature of these sources in more detail necessitates numerical tools complementary to analytical one-zone modelling efforts. In this paper, we introduce an open-source Python package tailored to this purpose, FLAREMODEL. The core of the code consists of low-level utility functions to describe physical processes relevant to synchrotron sources, which are written in C for performance and parallelised with OpenMP for scalability. The Python interface provides access to these functions and built-in source models are provided as a guidance. At the same time, the modular design of the code and the generic nature of these functions enable users to build a variety of source models applicable to many astrophysical synchrotron sources. We describe our methodology and the structure of our code along with selected examples demonstrating capabilities and options for future modelling efforts.

Modeling of Diffuse Auroral Emission at Mars: Contribution of MeV Protons

AbstractThe Solar Energetic Particle and imaging ultraviolet spectrograph (IUVS) instruments onboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft discovered diffuse aurora that span across the nightside of Mars due to the interaction of solar energetic particles (SEPs) with the Martian atmosphere. However, it is unclear whether the diffuse aurora originates from energetic electrons or protons. We have developed a Monte Carlo model to calculate the limb intensity profile of the CO2+ ultraviolet doublet (UVD) due to precipitation of energetic electrons and protons with energy ranges from 100 eV to 100 keV and from 50 keV to 5 MeV, respectively. We used electron and proton fluxes observed by MAVEN during the December 2014 SEP event and the September 2017 SEP event. Our results showed that proton‐induced CO2+ UVD emission has a lower peak altitude than electron‐induced CO2+ UVD emission. The calculated peak altitudes of the CO2+ UVD limb profiles are 76 and 68 km in the December 2014 event and the September 2017 event, respectively. Extending the energy to 500 keV for electrons and 20 MeV for protons further improved our comparison to the IUVS observations. We have succeeded in reproducing peak altitudes and shapes of the observed CO2+ UVD limb profiles using the SEP flux observed by MAVEN. This was possible by taking into account the contribution of energetic protons, indicating that both energetic electrons and protons contribute to producing the observed diffuse aurora.

Space weathering on inner planetary surface analogues induced by swift multicharged heavy ion bombardment

Silicates are ubiquitous in space. They dominate the surfaces of the inner rocky planets (Mercury in the case of the Solar System), the Moon, and asteroids, forming the major part of the non-volatile material. The physical and chemical properties of the rocky surfaces are determined not only by their initial composition but also by the processes occurring on them. Here we discuss one of these processes; irradiation by energetic cosmic particles that induces many effects among which structural changes and sputtering, the latter contributing to the formation of exospheres. In the current work we report the results of experiments conducted on anorthite, jadeite and nepheline silicates that have been irradiated with energetic heavy ions with the aim to better understand the interaction of galactic cosmic rays, solar wind, and solar energetic particles with planetary and small body surfaces. The sputtering effects induced by energetic (MeV/u) multicharged heavy ions (e.g., 105Rh and 140Ba) were analyzed by the PDMS-TOF-SIMS technique (plasma desorption mass spectrometry - time-of-flight secondary ion mass spectrometry). Positive and negative secondary ionic species are identified: Na+, K+, Al+, Ca+, SiO2−. Ejection of (SiO2)n− and (AlSi)Om− cluster series are also observed. Less frequent, negative ion yields are one order of magnitude less than positive ones, or greater, which is the case for nepheline, with 0.671 ions impact−1 for positive and 0.126 ions impact−1 for negative ions. The results concerning ejection of ionic species show, for instance, that the Na+/K+ ratio is ~2.5, which is in very good agreement with that observed in the Hermean exosphere found to be ~2.3.

An 18.3 MJ charging and discharging pulsed power supply system for the Space Plasma Environment Research Facility (SPERF): The subsystem for the magnetic perturbation coils.

The mechanism of acceleration, loss, and wave-particle interaction of energetic particles in the magnetosphere is a research content of the Space Plasma Environment Research Facility, which is being built as a user facility at the Harbin Institute of Technology in China. Two magnetic perturbation coils are used to simulate the magnetic storm distortion and excite Alfvén wave perturbation. A capacitor-based pulsed power supply (PPS) system with a modular designis developed to excite the magnetic perturbation coils to generate the required amplitude and duration of the magnetic field. The two magnetic perturbation coils are the CRDI coil and CRDII coil and are excited by one set of PPSs. The PPS for the CRDI coil consists of two modules and can provide a pulsed current of no less than 132 kA at 0.12ms when the charging voltage is 20 kV, and the duration of the pulsed current from the peak to 10% of the peak is no more than 0.7ms. The PPS for the CRDII coil consists of five modules and can provide a pulsed current of no less than 16 kA at 0.45, 0.65, 0.8, 0.95, and 1.1ms, and the duration of the pulsed current from the peak to 10% of the peak is no more than 4.5ms. The detailed designof the PPSs has been discussed in this paper, and the discharge test of the PPSs is carried out to verify the designof the PPSs.

On the wave-particle interaction and removal of energetic particles

There is always a risk of destruction of man-made satellites by the energetic electrons trapped in Van Allen radiation belts in space. These energetic electrons also pose a biological danger to astronauts. The cyclotron resonance interaction is studied between the whistler-mode waves in the frequency range of ELF (Extremely Low Frequency 300 – 3000 HZ) and VLF (Very Low Frequency 3 – 30 kHz) propagating along geomagnetic field line and counter streaming energetic electron. During this process the pitch angle of energetic electrons reduces. This results in the dumping of these electrons into the lower ionosphere. This makes electrons unable to strike the satellites orbiting in low Earth orbit, Geosynchronous, Sun-synchronous or polar orbit. It is shown that the lifetime values of energetic electrons vary from 2.03 to 227.68 hours at low latitudes. It is shown that these waves can remove these energetic electrons from their path and ensure the safety of satellites.

A Focused Transport-based Kinetic Fractional Diffusion-advection Equation for Energetic Particle Trapping and Reconnection-related Acceleration by Small-scale Magnetic Flux Ropes in the Solar Wind

Abstract Analysis of energetic particle inner heliospheric spacecraft data increasingly suggests the existence of anomalous diffusion phenomena that should be addressed to achieve a better understanding of energetic particle transport and acceleration in the expanding solar wind medium. Related to this is fast-growing observational evidence supporting the long-standing prediction from magnetohydrodynamic (MHD) theory and simulations of the presence of an inner heliospheric, dominant quasi-two-dimensional MHD turbulence component that contains coherent contracting and merging (reconnecting) small-scale magnetic flux rope (SMFR) structures. This suggests that energetic particle trapping in SMFRs should play a role in anomalous diffusion in the solar wind that warrants further investigation. However, progress in studying such anomalous energetic particle transport phenomena in the solar wind is hampered by the lack of a fundamental derivation of a general fractional kinetic transport equation linking macroscopic energetic particle fractional transport to the microscopic physics of energetic particle interaction with SMFR structures. Here, we outline details of how one can derive a closed ensemble-averaged focused transport equation in the form of a general kinetic fractional diffusion-advection equation from first principles following the nonlinear Eulerian correlation function closure approach of Sanchez et al. With this equation one can model the anomalous diffusion of energetic particles in ordinary, momentum, and pitch-angle space in response to particle trapping in numerous SMFRs advected with the solar wind flow.

MITO: a new directional muon telescope

Muon telescopes are instruments devoted to the observation of muons. They are produced in the atmosphere by means of the interaction of cosmic ray and solar energetic particles with atmospheric nuclei. Muons, as cosmic rays that produce them, present non uniform arrival directions and temporal variations at ground level and, along certain observation directions, could forecast the arrival of interplanetary coronal mass ejections (ICMEs) at the Earth, even earlier than neutron monitors. However, multidirectional muon telescopes are not easily affordable because of their complexity, size and cost. In this work, we present the muon impact tracer and observer (MITO) design concept. It is composed of only two stacked scintillators (1 m2) with an optional lead layer that allows the filtering of unwanted particles depending on the type of application. In the case presented here, a 10 cm lead layer corresponding to the lead of a 3NM64 neutron monitor around which MITO has been built. Eight photomultipliers (PMTs) gather the light emerging from the four lateral sides of the scintillators. MITO has been conceived not only to achieve muon flux registering, but also to register muon arrival directions through the capture and analysis of multiple PMT pulse height data. The number of scintillators and electronic components is reduced, simplifying its design and construction and reducing complexity, volume, weight, power consumption and cost, and thus, achieving a reasonable performance-cost ratio in comparison to other directional telescopes based on two-layer matrices. The first prototype was shipped from Spain to Antarctica where it is now recording data. Some preliminary results are also presented.

Multi‐Parameter Chorus and Plasmaspheric Hiss Wave Models

AbstractThe resonant interaction of energetic particles with plasma waves, such as chorus and plasmaspheric hiss waves, plays a direct and crucial role in the acceleration and loss of radiation belt electrons that ultimately affect the dynamics of the radiation belts. In this study, we use the comprehensive wave data measurements made by the Electric and Magnetic Field Instrument Suite and Integrated Science instruments on board the two Van Allen probes, to develop multi‐parameter statistical chorus and plasmaspheric hiss wave models. The models of chorus and plasmaspheric hiss waves are presented as a function of combined geomagnetic activity (AE), solar wind velocity (V), and southward interplanetary magnetic field (Bs). The relatively smooth wave models reveal new features. Despite, the coupling between geomagnetic and solar wind parameters, the results show that each parameter still carries a sufficient amount of unique information to more accurately constrain the chorus and plasmaspheric hiss wave intensities. The new wave models presented here highlight the importance of multi‐parameter wave models, and can improve radiation belt modeling.

Reliability-driven pin assignment optimization to improve in-orbit soft-error rate

Electronics are increasingly susceptible to energetic particle interactions within the silicon. In order to improve the circuit reliability under radiation effects, several hardening techniques have been adopted in the design flow of VLSI systems. This paper proposes a pin assignment optimization in logic gates to reduce the Single-Event Transient (SET) cross-section and improve the in-orbit soft-error rate. Signal probability propagation is used to assign the lowest probability to the most sensitive input combination of the circuit by rewiring or pin swapping. The cell optimization can reach up to 48% reduction on the soft-error rate. For the analyzed arithmetic benchmark circuits, an optimized cell netlist can achieve from 8% to 28% reduction on the SET cross-section and in-orbit soft-error rate at no cost in the circuit design area. Additionally, as the pin swapping is a layout-friendly technique, the optimization does not impact on the cell placement and it can be adopted along with other hardening techniques in the logic and physical synthesis.

Meteoritic evidence of a late superflare as source of 7Be in the early Solar System

Fossil meteoritic records of short-lived, now-extinct radionuclides provide crucial high-resolution temporal information about the events, processes and activity of the Sun during the early phases of Solar System formation1. The proposed genesis of one such radionuclide,10Be, by spallation reactions of carbon and oxygen2–5 led to the hypothesis of enhanced irradiation in the early Solar System6–8. An alternative scenario of production of 10Be (half-life t1/2 = 1.386 ± 0.016 million years9) by a neutrino process in a supernova arising from the core collapse of a low-mass star (11.8 solar masses, M⊙) has recently been suggested10 and can explain the observed abundance of 10Be in the early Solar System. Here, we report well-resolved excesses in 7Li/6Li of up to ~21.5% in a calcium- and aluminium-rich inclusion (CAI) from the Efremovka meteorite that correlate with 9Be/6Li, suggestive of in situ decay of 7Be. The in situ decay of 7Be to 7Li, with a characteristic half-life of 53.12 ± 0.07 days11, entails multiple episodes of enhanced irradiation in the early Solar System, which have been observed recently in other Sun-like stars12,13. The short half-life of 7Be limits its production by interaction of solar energetic particles (SEPs) with the nebular gas and solids, and provides constraints on the genealogy and chronology of CAIs. Irradiation of the solid and gaseous precursors of CAIs of solar composition by a superflare (X-ray luminosity approximately 1032 erg s−1) during the terminal phase of class I or II of the pre-main-sequence stages of the Sun explains the isotopic properties, distinctive petrographic features and diffusivity constraints in the CAI. Li and Be isotopic measurements of calcium–aluminium inclusions (CAIs) in the Efremovka meteorite suggest that the solid and gaseous precursors of CAIs were irradiated by a superflare during the last stages of the pre-main-sequence evolution of the Sun.

Hadronic Interactions of Energetic Charged Particles in Protogalactic Outflow Environments and Implications for the Early Evolution of Galaxies

We investigate the interactions of energetic hadronic particles with the media in outflows from star-forming protogalaxies. These particles undergo pion-producing interactions which can drive a heating effect in the outflow, while those advected by the outflow also transport energy beyond the galaxy, heating the circumgalactic medium. We investigate how this process evolves over the length of the outflow and calculate the corresponding heating rates in advection-dominated and diffusion-dominated cosmic ray transport regimes. In a purely diffusive transport scenario, we find the peak heating rate reaches $10^{-26}\;\! {\rm erg~cm}^{-3}\;\! {\rm s}^{-1}$ at the base of the outflow where the wind is driven by core-collapse supernovae at an event rate of 0.1 $\text{yr}^{-1}$, but does not extend beyond 2 kpc. In the advection limit, the peak heating rate is reduced to $10^{-28}\;\! {\rm erg~cm}^{-3}\;\! {\rm s}^{-1}$, but its extent can reach to tens of kpc. Around 10% of the cosmic rays injected into the system can escape by advection with the outflow wind, while the remaining cosmic rays deliver an important interstellar heating effect. We apply our cosmic ray heating model to the recent observation of the high-redshift galaxy MACS1149-JD1 and show that it could account for the quenching of a previous starburst inferred from spectroscopic observations. Re-ignition of later star-formation may be caused by the presence of filamentary circumgalactic inflows which are reinstated after cosmic ray heating has subsided.

Energetic Ion Moments and Polytropic Index in Saturn's Magnetosphere using Cassini/MIMI Measurements: A Simple Model Based on κ‐Distribution Functions

AbstractMoments of the charged particle distribution function provide a compact way of studying the transport, acceleration, and interactions of plasma and energetic particles in the magnetosphere. We employ κ‐distributions to describe the energy spectra of H+ and O+, based on >20 keV measurements by the three detectors of Cassini's Magnetospheric Imaging Instrument, covering the time period from DOY 183/2004 to 016/2016, 5 < L < 20. From the analytical spectra we calculate the equatorial distributions of energetic ion moments inside Saturn's magnetosphere and then focus on the distributions of the characteristic energy (Ec=IE/In), temperature, and κ‐index of these ions. A semiempirical model is utilized to simulate the equatorial ion moments in both local time and L‐shell, allowing the derivation of the polytropic index (Γ) for both H+ and O+. Primary results are as follows: (a) The ∼9 < L < 20 region corresponds to a local equatorial acceleration region, where subadiabatic transport of H+ (Γ∼1.25) and quasi‐isothermal behavior of O+ (Γ∼0.95) dominate the ion energetics; (b) energetic ions are heavily depleted in the inner magnetospheric regions, and their behavior appears to be quasi‐isothermal (Γ<1); (c) the (quasi‐) periodic energetic ion injections in the outer parts of Saturn's magnetosphere (especially beyond 17–18 RS) produce durable signatures in the energetic ion moments; (d) the plasma sheet does not seem to have a ground thermodynamic state, but the extended neutral gas distribution at Saturn provides an effective cooling mechanism that does not allow the plasma sheet to behave adiabatically.