Energetic Particle Emission Research Articles

The Effect of the Ambient Solar Wind Medium on a CME-driven Shock and the Associated Gradual Solar Energetic Particle Event

We present simulation results of a gradual solar energetic particle (SEP) event detected on 2021 October 9 by multiple spacecraft, including BepiColombo (Bepi) and near-Earth spacecraft such as the Advanced Composition Explorer (ACE). A peculiarity of this event is that the presence of a high-speed stream (HSS) affected the low-energy ion component (≲5 MeV) of the gradual SEP event at both Bepi and ACE, despite the HSS having only a modest solar wind speed increase. Using the EUHFORIA (European Heliospheric FORecasting Information Asset) magnetohydrodynamic model, we replicate the solar wind during the event and the coronal mass ejection (CME) that generated it. We then combine these results with the energetic particle transport model PARADISE (PArticle Radiation Asset Directed at Interplanetary Space Exploration). We find that the structure of the CME-driven shock was affected by the nonuniform solar wind, especially near the HSS, resulting in a shock wave front with strong variations in its properties such as its compression ratio and obliquity. By scaling the emission of energetic particles from the shock to the solar wind compression at the shock, an excellent match between the PARADISE simulation and in situ measurements of ≲5 MeV ions is obtained. Our modeling shows that the intricate intensity variations observed at both ACE and Bepi were influenced by the nonuniform emission of energetic particles from the deformed shock wave and demonstrates the influence of even modest background solar wind structures on the development of SEP events.

SANTA: A safety analysis code for neutron absorbers in spent nuclear fuel pools

Recent experimental reports on the premature corrosion of an Al-B4C neutron absorber in a spent nuclear fuel pool, which was possibly assisted by 10B(n, α)7Li reaction-induced porous microstructures, illustrated the need for quantitative evaluation of the neutron-induced energetic particle emission reactions inside neutron absorbers. For this purpose, we developed a Safety Analysis code for NeuTron Absorbers in spent nuclear fuel pools (SANTA) by integrating several existing codes (TRITON, ORIGEN, CSAS6, and modified SDTrimSP) with newly developed modules to provide the essential parameters for the experimental emulation of irradiation-assisted corrosion of the absorbers. The most important outputs of this code are radiation damage in displacement per atom (dpa) units and He concentration in atomic ppm. These outputs are required for the design of heavy-ion irradiation experiments on the absorbers to emulate the radiation damage induced by energetic 7Li ions and α-particles. The SANTA code is also user-friendly: its whole sequence can be executed using simplified text-based input without user intervention. This code may improve the understanding of the gas bubble formation and irradiation-assisted corrosion mechanisms of the neutron absorbers, and it could provide a foundation for the future development of more robust safety codes for spent nuclear fuel pools.

Vertical characterization on global ionospheric variations during the magnetic storm in September 2017 with hierarchical subtraction method

This study investigates the global ionospheric responses at different altitudes during the geomagnetic storm in September 2017 by using the observations from IGS GIMs and GRACE, TerraSAR-X, COSMIC, Metop LEO satellite missions. According to different satellite heights, a hierarchical subtraction method is proposed to characterize the disturbance of total electron content (TEC) at the vertical regions of below 340 km , 340 ∼ 520 km , 520 ∼ 800 km and above 800 km , respectively. The integrated TEC from IRI-Plas2017 are applied to verify the feasibility and rationality of the proposed method and the electron density (Ne) profiles from the ionosonde and radio occultation (RO) measurements are used to explore the variations of Ne in different height regions. The resulting TEC disturbances ( Δ TEC) on a global scale show that: 1) There was significant increase on Ne peak in F2 region during the magnetic storm, due to the strong recombination in the lower ionosphere while more intense electron ionization in the upper ionosphere; 2) During the main phase, TEC enhancement had a tendency to drift westward, which may correlate with the twice Dst minimums. 3) The east–west and north–south hemispheric asymmetry of Δ TEC exist simultaneously in this magnetic storm. However, the former is mainly attributed to ionospheric plasma bubbles, while the latter might be the seasonal thermospheric effects or the energetic particle emissions.

Acceleration of Solar Energetic Particles through CME-driven Shock and Streamer Interaction

Abstract On 2013 June 21, a solar prominence eruption was observed, accompanied by an M2.9 class flare, a fast coronal mass ejection, and a type II radio burst. The concomitant emission of solar energetic particles (SEPs) produced a significant proton flux increase, in the energy range 4–100 MeV, measured by the Low and High Energy Telescopes on board the Solar TErrestrial RElations Observatory (STEREO)-B spacecraft. Only small enhancements, at lower energies, were observed at the STEREO-A and Geostationary Operational Environmental Satellite (GOES) spacecraft. This work investigates the relationship between the expanding front, coronal streamers, and the SEP fluxes observed at different locations. Extreme-ultraviolet data, acquired by the Atmospheric Imaging Assembly (AIA) instrument on board the Solar Dynamics Observatory (SDO), were used to study the expanding front and its interaction with streamer structures in the low corona. The 3D shape of the expanding front was reconstructed and extrapolated at different times by using SDO/AIA, STEREO/Sun Earth Connection Coronal and Heliospheric Investigation, and Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph observations with a spheroidal model. By adopting a potential field source surface approximation and estimating the magnetic connection of the Parker spiral, below and above 2.5 R ⊙, we found that during the early expansion of the eruption, the front had a strong magnetic connection with STEREO-B (between the nose and flank of the eruption front) while having a weak connection with STEREO-A and GOES. The obtained results provide evidence, for the first time, that the interaction between an expanding front and streamer structures can be responsible for the acceleration of high-energy SEPs up to at least 100 MeV, as it favors particle trapping and hence increases the shock acceleration efficiency.

Heliospheric effects caused by Sun-originating versus LISM-advected fluctuations

Context. We investigate the response of the heliosphere to fluctuations in the local interstellar medium (LISM) as compared to the influence of solar-cycle fluctuations. Aims. We discuss the differences between effects coming from the two types of drivers of time-dependent effects in the heliosphere in the context of the shape of the heliosphere, the thickness of the inner heliosheath, and the position of the ribbon of enhanced energetic neutral particle emission, as observed by the IBEX mission. Methods. Our study is based on a comparison of fully time-dependent simulations obtained with a three-dimensional (3D) model of the heliosphere. Results. We show that density fluctuations, taking the form of entropy waves and originating from the LISM, may reduce the thickness of the inner heliosheath to a similar extent as the solar-cycle effects. However, the relative motions of the termination shock and the heliopause in the two types of simulations are different. The amplitude of variation of the heliopause position is greater for the LISM fluctuation. The IBEX ribbon position is shown to be not significantly affected by the two types of drivers, although the effect of LISM fluctuation is stronger than that of the solar cycle. In this context, slight systematic changes of the position of the IBEX ribbon in its different sectors (i.e., changes in the heliospheric nose followed by variations in the heliospheric flanks) may serve as an indicator of the passage of a density fluctuation in the LISM, as suggested by our study. We also discuss the difficulties in fitting the LISM parameters in the presence of time-dependent effects.

The imaging fast ion D-alpha diagnostic (IFIDA) on DIII-D.

An Imaging Fast Ion D-alpha (IFIDA) diagnostic, characterized by a high optical spatial resolution of ≤2 mm for accurate validation of energetic particle (EP) transport models, has been developed on DIII-D. The diagnostic provides a 2D image in the radial-poloidal plane of the FIDA signal generated by EP emission after charge exchange with an injected neutral beam. A narrow passband filter integrates the FIDA signal in the spectral region of 650-652nm (blue-shifted FIDA tail), which is mostly generated by co-passing EPs of energies E ≃ 40-80 keV. A beam modulation technique is employed to estimate the active component of the signal, which is then used to compute EP profiles and gradients with a higher accuracy than the standard spectroscopic FIDA diagnostic. The current diagnostic time resolution is ≃3 ms. In this work, the IFIDA diagnostic design is explained and data are compared with the spectroscopic FIDA diagnostic, which shares the same viewing geometry, to assess the improvements in EP profile reconstruction.

PenNuc: Monte Carlo simulation of the decay of radionuclides

The Fortran subroutine package PenNuc that performs Monte Carlo simulation of the decay of radioactive nuclides is described. The adopted nuclear decay characteristics (possible disintegration modes and branching ratios, energies and half-lives of nuclear energy levels, types and energies of emitted particles) are from the nucleide evaluated database ( http://www.nucleide.org/DDEP_WG/DDEPdata.htm) in the specific format PenNuc. The initial energies of electrons and positrons emitted in beta disintegrations are sampled from their continuous spectra by means of the RITA (rational inverse transform with aliasing) algorithm, which is described in the Appendix. Electronic relaxation of the residual ion after electron capture and internal conversion is simulated by using the data and sampling methods of the penelope code system. At each call the subroutines deliver a list of state variables of the particles (photons, electrons, positrons and alphas) emitted in a random decay path of the considered radionuclide down to a metastable level or to the ground state of the daughter nucleus. The distribution package includes a main program that simulates the emission spectrum of a radionuclide and, optionally, produces a list of particles emitted in a prescribed number of decays. Program summaryProgram Title: PenNucProgram Files doi:http://dx.doi.org/10.17632/dy28h8xmkv.1Licensing provisions: CC by NC 3.0Programming language: Fortran 90/95Nature of problem:PenNuc simulates the emission of energetic particles in random decay pathways of radionuclides. The initial state of a particle is described by the following variables: type of particle (photon, electron, positron, or alpha), energy, direction, and emission time relative to the start of the decay. For each decay the program provides a list of initial states of the particles emitted with energies higher than the adopted cutoff ECNUC, which is set to 200 eV in the original source file.Solution method: The nuclear disintegration mode and the subsequent de-excitation of the daughter nucleus are simulated by using decay information from the nucleide evaluated databases. De-excitation of ions produced in electron capture and internal conversion is simulated by using atomic transition data and sampling methods from the Monte Carlo code system penelope [1]. The energy of beta particles is sampled using the RITA (rational inverse transform with aliasing) algorithm, which optimizes both simulation speed and accuracy.Additional comments: Although PenNuc can describe several radionuclides simultaneously, the selection of the active nuclide (appropriate to the characteristics of the radioactive source) must be done in the main program. The subroutines provide the complete set of particles emitted with energies higher than the cutoff ECNUC in each nuclear decay, including x rays and Auger electrons.[1] F. Salvat, penelope-2014: A code System for Monte Carlo Simulation of Electron and Photon Transport, OECD/NEA Data Bank, Issy-les-Moulineaux, France, 2015. Available from http://www.nea.fr/lists/penelope.html.

Scaling-laws of Radio Spike Bursts and Their Constraints on New Solar Radio Telescopestwo

Radio observation is one of important methods in solar physics and space science. Sometimes, it is almost the sole approach to observe the physical processes such as the acceleration, emission, and propagation of non-thermal energetic particles, etc. So far, more than 100 solar radio telescopes have been built in the world, including solar radiometers, dynamic spectrometers, and radioheliographs. Some of them have been closed after the fulfillment of their primary scientific objectives, or for their malfunctions, and thus replaced by other advanced instruments. At the same time, based on some new technologies and scientific ideas, various kinds of new and much more complicated solar radio telescopes are being constructed by solar radio astronomers and space scientists, such as the American E-OVSA and the solar radio observing system under the framework of Chinese Meridian Project II, etc. When we plan to develop a new solar radio telescope, it is crucial to design the most suitable technical parameters, e.g., the observing frequency range and bandwidth, temporal resolution, frequency resolution, spatial resolution, polarization degree, and dynamic range. Then, how do we select a rational set of these parameters? The long-term observation and study revealed that a large strong solar radio burst is frequently composed of a series of small bursts with different time scales. Among them, the radio spike burst is the smallest one with the shortest lifetime, the narrowest bandwidth, and the smallest source region. Solar radio spikes are considered to be related to a single magnetic energy release process, and can be regarded as an elementary burst in solar flares. It is a basic requirement for the new solar radio telescope to observe and discriminate these solar radio spike bursts, even though the temporal and spatial scales of radio spike bursts actually vary with the observing frequency. This paper presents the scaling laws of the lifetime and bandwidth of solar radio spike bursts with respect to the observing frequency, which provide some constraints for the new solar radio telescopes, and help us to select the rational telescope parameters. Besides, we propose a spectrum-image combination mode as the best observation mode for the next-generation solar radio telescopes with high temporal, spectral, and spatial resolutions, which may have an important significance for revealing the physical essence of the various non-thermal processes in violent solar eruptions.

Montecarlo simulation of the High Energy Particle Detector on board the satellite CSES

The High-Energy Particle Detector (HEPD) is an instrument devoted to the measurement of cosmic particles from few MeV up to hundreds of MeV. The HEPD will contribute to the China Seismo-Electromagnetic Satellite mission by measuring the precipitation of trapped particles and by studying the solar-terrestrial environment especially during impulsive events like coronal mass ejections and solar energetic particle emissions. A Monte Carlo software was realized to study the performance of HEPD, such as its particle discrimination capability, the energy threshold for trigger and the maximum energy detectable in full containment. This contribution reports the main features of the HEPD Monte Carlo simulation and some results of the detector performance based on it. A comparison with beam tests was carried out, showing a good agreement with the simulation.

Introducing adaptive neurofuzzy modeling with online learning method for prediction of time-varying solar and geomagnetic activity indices

Research in space weather has in recent years become an active field of research requiring international cooperation because of its importance in hazard warning especially for satellite technology and power utility systems. The time-varying sun as the main source of space weather impacts the Earth’s magnetosphere by emitting hot magnetized plasma called solar wind into interplanetary space. The emission of Solar Energetic Particles (SEPs) and consequently the magnitude of Interplanetary Magnetic Field (IMF) vary almost periodically with an approximate life cycle of 11 years. It is shown that the solar and geomagnetic activity indices have complex behavior often characterizable as quasi-periodic or even chaotic, which causes the long-term prediction to be a conundrum. Moreover, solar and geomagnetic activity indices and their chaotic characteristics vary abruptly during solar and geomagnetic storms. This variation depicts the difficulties in modeling and long-term prediction of solar and geomagnetic storms. On the other hand, neural networks and related neurofuzzy tools as general function approximators have been the subjects of interest due to their many practical applications in modeling and predicting complex phenomena. However, most of these systems are trained by algorithms that need to be carried out by an off-line data set which influence their performance in prediction of time-varying solar and geomagnetic activity indices. This paper proposes an adaptive neurofuzzy approach with a recursive learning algorithm for modeling and prediction of space weather indices which fulfill requirements of prediction of time-varying solar and geomagnetic activities for long time spans. The obtained results depict the power of the proposed method in online prediction of time-varying solar and geomagnetic activity indices.

Triple tracks in CR-39 as the result of Pd–D Co-deposition: evidence of energetic neutrons

Since the announcement by Fleischmann and Pons that the excess enthalpy generated in the negatively polarized Pd-D-D(2)O system was attributable to nuclear reactions occurring inside the Pd lattice, there have been reports of other manifestations of nuclear activities in this system. In particular, there have been reports of tritium and helium-4 production; emission of energetic particles, gamma or X-rays, and neutrons; as well as the transmutation of elements. In this communication, the results of Pd-D co-deposition experiments conducted with the cathode in close contact with CR-39, a solid-state nuclear etch detector, are reported. Among the solitary tracks due to individual energetic particles, triple tracks are observed. Microscopic examination of the bottom of the triple track pit shows that the three lobes of the track are splitting apart from a center point. The presence of three alpha-particle tracks outgoing from a single point is diagnostic of the (12)C(n,n')3alpha carbon breakup reaction and suggests that DT reactions that produce > or = 9.6 MeV neutrons are occurring inside the Pd lattice. To our knowledge, this is the first report of the production of energetic (> or = 9.6 MeV) neutrons in the Pd-D system.

Energetic particle and photon emission during dense plasma formation at the ferroelectric surface

The operation of ferroelectric plasma sources (FPSs) under the application of driving pulses with different amplitudes (4–40 kV) was studied. It was found that the dense plasma formation during the fast fall (a few tens of nanoseconds) in the driving pulse is accompanied by the generation of a highly diverging (∼180°) neutral flow with a velocity of ∼7 × 107 cm s−1 in addition to the electron/ion and charged micro-particle flows which were studied in earlier research. It was shown that the velocity and intensity of the generated neutral flow remained the same for different parameters of the driving pulse. In addition a flux of x-rays with an energy of ∼20 keV was observed for ∼2 µs after the ending of the 40 kV driving pulse. A model of neutral emission based on micro-explosions of ferroelectric ceramics is suggested.

Use of CR-39 in Pd/D co-deposition experiments

The use of CR-39, a solid state nuclear track detector, to detect the emission of energetic charged particles during Pd/D co-deposition is demonstrated. The pits observed in the CR-39 are attributed to the Pd/D cathode and are not due to radionuclide contamination in the cell components; nor to the impingement of D2 bubbles on the surface of the CR-39; nor to chemical attack by D2, O2, or Cl2. The features (i.e., optical contrast, shape, and bright spot in the center of the pit) of the pits generated during Pd/D co-deposition are consistent with those observed for pits that are of a nuclear origin.

Characterization of doping levels in heteronuclear, gas-phase, van der Waals clusters and their energy absorption from an intense optical field

A simple mass spectrometric method has been developed to quantify dopant levels in heteronuclear clusters in the gas phase. The method is demonstrated with reference to quantification of the water content in supersonic beams of water-doped argon clusters. Such doped clusters have assumed much importance in the context of recently-reported doping-induced enhancement in the emission of energetic charged particles and photons upon their interaction with intense laser pulses. We have also measured the energy that a doped cluster absorbs from the optical field; we find that energy absorption increases with increasing level of doping. The oft-used linear model of energy absorption is found to be quantitatively inadequate.

Multi-fluid shocks in clusters of galaxies: Entropy, σv–T, M–T and LX–T scalings

Abstract The nonthermal phenomena in clusters of galaxies are considered in the context of the hierarchical model of cosmic structure formation by accretion and merging of the dark matter (DM) substructures. Accretion and merging processes produce large-scale gas shocks. The plasma shocks are expected to be collisionless. In the course of cluster’s aggregation, the shocks, being the main gas-heating agent, generate turbulent magnetic fields and accelerate energetic particles via collisionless multi-fluid plasma relaxation processes. The intracluster gas heating and entropy production rate by a collisionless shock may differ significantly from that in a single-fluid collisional shock. Simple scaling relations for postshock ion temperature and entropy as functions of shock velocity in strong collisionless multi-fluid shocks are presented. We show that the multi-fluid nature of the collisionless shocks results in high gas compression, reduced entropy production and modified σ v – T , M – T and L X – T scalings. The scaling indexes estimated for a simple model of a strong accretion multi-fluid shock are generally consistent with observations. Soft X-ray and extreme ultraviolet photons dominate the emission of strong accretion shock precursors that appear as large-scale filaments. Magnetic fields, turbulence and energetic particles constitute the nonthermal components contributing into the pressure balance, energy transport and emission of clusters. Nonthermal emission of energetic particles could be a test to constrain the cluster properties.

Transport and Acceleration of Solar Energetic Particles from Coronal Mass Ejection Shocks

After a brief overview of solar energetic particle (SEP) emission from coronal mass ejection (CME) shocks, we turn to a discussion of their transport and acceleration. The high energy SEP are accelerated near the Sun, and because of their well-known source location, their transport can be modeled quantitatively to obtain precise information on the injection function (number of particles emitted vs. time), including a determination of the onset time to within 1 min. For certain events, transport modeling also indicates magnetic topology with mirroring or closed field loops. Important progress has also been made on the transport of low energy SEP from very strong events, which can display exhibit interesting saturation effects and compositional variations. The acceleration of SEP by CME-driven shocks in the interplanetary medium is attributed to diffusive shock acceleration, but the spectrum of SEP production is typically modeled empirically. Recent progress has largely focused on using detailed composition measurements to determine fractionation effects of shock acceleration and even to clarify the nature of the seed population. In particular, there are many indications that the seed population is suprathermal (pre-energized) and the injection problem is not relevant to acceleration at interplanetary CME-driven shocks. We argue that the finite time available for shock acceleration provides the best explanation of the high-energy rollover.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Energetic particle emission and nuclear dynamics around the Fermi energy

Energetic particle emission and nuclear dynamics around the Fermi energy

Energetic particle emission and nuclear dynamics around the Fermi energy

Energetic proton emission was investigated in the reaction 58Ni+ 58Ni at 30 AMeV and compared with the results of dynamical calculations with a momentum dependent mean field. Preliminary results on proton and intermediate mass fragment coincidences are also presented.

Optimized energetic particle emissions from Xe clusters in intense laser fields

We have probed the interaction of intense laser fields with Xe clusters by measuring the energy and charge state distributions of emitted ions and electrons using ultrafast 20-fs pulses. This work demonstrates that the energetic particle emissions from laser-cluster interactions can be optimized by manipulating the character of ultrafast laser pulses, i.e., pulse duration and sign of chirp. The mean and maximum ion energies as high as 0.1 and 2 MeV, respectively, are achieved when Xe clusters are irradiated by 500-fs pulses with negative chirp as an optimal condition under a laser peak intensity of $2\ifmmode\times\else\texttimes\fi{}{10}^{17}{\mathrm{W}/\mathrm{c}\mathrm{m}}^{2}.$ The mean ion energy obtained from 500-fs pulses with negative chirp is found to be about 1.6 times larger than that with positive chirp.

The correlation functions and emission time scales for light particles and light fragments in 40Ar+ 197Au reactions at 25 MeV/nucleon

Two-particle correlation functions were measured for the emission of protons, deuterons, tritons, α, and lithium fragment at small relative momenta in 40Ar-induced reactions on 197Au at 25 MeV/nucleon. Based on three-body trajectory calculations the emission time scales for the particles were extracted from p-d, d-d, t-t, and lithium-lithium correlation functions. The mean emission time was found to decrease with increasing sum of the kinetic energies of the particle in a correlated pairs, indicating the emission of more energetic particles at earlier stages of the reaction than at later stages. The time scale for the emission of lithium fragments emission suggests that sequential binary disassembly occurs in 40Ar+ 197Au reaction at MeV/nucleon. Mean emission temperature of 3.5 −0.8 +1.3 and 3.6±0.4 MeV were also extracted from the relative populations of the excited and ground states of the respective emitted nuclides 8Be and 4He.