High-energy Electron Flux Research Articles

An operational approach to forecast the Earth’s radiation belts dynamics

The Ca index is a time-integrated geomagnetic index that correlates well with the dynamics of high-energy electron fluxes in the outer radiation belts. Therefore, Ca can be used as an indicator for the state of filling of the radiation belts for those electrons. Ca also has the advantage of being a ground-based measurement with extensive historical records. In this work, we propose a data-driven model to forecast Ca up to 24 h in advance from near-Earth solar wind parameters. Our model relies mainly on a recurrent neural network architecture called Long Short Term Memory that has shown good performances in forecasting other geomagnetic indices in previous papers. Most implementation choices in this study were arbitrated from the point of view of a space system operator, including the data selection and split, the definition of a binary classification threshold, and the evaluation methodology. We evaluate our model (against a linear baseline) using both classical and novel (in the space weather field) measures. In particular, we use the Temporal Distortion Mix (TDM) to assess the propensity of two time series to exhibit time lags. We also evaluate the ability of our model to detect storm onsets during quiet periods. It is shown that our model has high overall accuracy, with evaluation measures deteriorating in a smooth and slow trend over time. However, using the TDM and binary classification forecast evaluation metrics, we show that the forecasts lose some of their usefulness in an operational context even for time horizons shorter than 6 h. This behaviour was not observable when evaluating the model only with metrics such as the root-mean-square error or the Pearson linear correlation. Considering the physics of the problem, this result is not surprising and suggests that the use of more spatially remote data (such as solar imaging) could improve space weather forecasts.

Formation of Luminescing High-Temperature Ceramics upon Exposure to Powerful High-Energy Electron Flux

It is shown that MgF2 and YAG:Ce ceramics is synthesized with a high rate from the charge with low bulk density irradiated by powerful flux of electrons with energy of 1.4 MeV. High efficiency of synthesis is caused by the formation of radiolysis products stimulating solid- and gas-phase reactions in the charge upon exposure to powerful radiation fluxes.

Machine Learning for the Relationship of High-Energy Electron Flux between GEO and MEO with Application to Missing Values Imputation for Beidou MEO Data

AbstractWe consider the problem of building the relationship of high-energy electron flux between Geostationary Earth Orbit (GEO) and Medium Earth Orbit (MEO). A time-series decomposition technique is first applied to the original data, resulting in trend and detrended part for both GEO and MEO data. Then we predict MEO trend with GEO data using three machine learning models: Linear Regression (LR), Random Forest (RF), and Multi-Layer Perceptron (MLP). Experiment shows that RF gains best performance in all scenarios. Feature extraction analysis demonstrates that the inclusion of lagged features and (possible) ahead features is substantially helpful to the prediction. At last, an application of imputing missing values for MEO data is presented, in which RF model with selected features is used to handle the trend part while a moving block method is for the detrended part.

A stratospheric and satellite CubeSat format probe for detecting relativistic runaway electron avalanches

In planetary atmospheres, runaway electron avalanches could happen due to large scale electric fields, which accelerate electrons to energies about 0,1 – 10 MeV. This phenomenon is not fully understood. Nowadays, most of the satellite data is obtained on low orbits. However, runaway breakdown can also occur at altitudes less than 30 km. In this case, most of the radiation is scattered without reaching the satellites on high orbits. The formation of charged particles in the atmosphere can affect the results of numerous experiments. Therefore, it is important to have the most proper model of this phenomenon. Project goal is to create a stratospheric CubeSat format probe capable of detecting these events at an altitude of about 30 km and above. The purpose of the experiment is to observe changes in the fluxes of both high-energy electrons and radiation, as well as an analysis of possible correlations of the measured parameters. We developed a concept of the probe and created a detector prototype, consisting of a thick polystyrene scintillation counter wrapped in mylar and two SiPM SensL MicroSB-30035-X13 readout.

Weak Violation of Electroneutrality in the Heliogeospheres: Electroneutrality Disorders

We prove that the occurrence of constant fluxes of positive ions with a large ratio of the charge number (Z) to the mass number of the ion (M) --- Z/M in the solar wind (SW) is due to an insignificant violation of the electroneutrality of the Sun and the entire heliosphere, the absence of Debye shielding of the solar charge due to due to the presence of a constant flux (current) of high-energy electrons from the Sun throughout the heliosphere and the appearance for protons, alpha particles and other positive ions with a ratio Z/M ≥ 0.107, Coulomb mirrors that reflect and accelerate them reflecting and accelerating them from the Sun. For the first time, the effective charge (1.4 kC) and other parameters of a positively charged Sun, which make it possible to estimate the electric field strength (E/N) reduced to particle density (N), were calculated from the ionic composition of SW (according to the minimum Z/M positive ions observed in experiments). This model allowed us to estimate the electric field intensity (E/N) reduced to the density of particles N in the photosphere, chromosphere, corona of the Sun (E/N ≈ 27· 103 Td), heliosphere and to investigate the conditions necessary for reflection of various positively charged particles --- ions from the positively charged Sun

Electric and magnetic axion quark nuggets, their stability and their detection

The present work studies the dynamics of axion quark nuggets introduced in Zhitnitsky (JCAP 0310:010, 2003) and developed further in the works (Zhitnitsky in Phys Rev D 74:043515, 2006; Lawson and Zhitnitsky in Phys Lett B 724, 17, 2013; Lawson and Zhitnitsky in Phys Rev D 95:063521, 2017; Liang and Zhitnitsky in Phys Rev D 94:083502, 2016; Ge et al. in Phys Rev D 97:043008, 2018; Zhitnitsky in Phys Dark Univ 22:1, 2018; Lawson and Zhitnitsky in Phys Dark Univ 100295, 2019; Raza et al. in Phys Rev D 98:103527, 2018; Fischer et al. in Phys Rev D 98:043013, 2018; van Waerbeke and Zhitnitsky in Phys Rev D 99:043535, 2019; Flambaum and Zhitnitsky in Phys Rev D 99:043535, 2019; Lawson and Zhitnitsky in JCAP 02:049, 2017; Ge et al. in Phys Rev D 99:116017, 2019). The new feature considered here is the possibility that these nuggets become ferromagnetic. This possibility was pointed out in Tatsumi (Phys Lett B 489:280 2000) for ordinary quark nuggets, although ferromagnetism may also take place due some anomaly terms found in Son and Zhitnitsky (Phys Rev D 70:074018, 2004), Son and Stephanov (Phys Rev D 77:014021, 2008) and Melitski and Zhitnitsky (Phys Rev D 72:045011, 2005). The purpose of the present letter however, is not to give evidence in favor or against these statements. Instead, it is focused in some direct consequences of this ferromagnetic behavior, if it exists. The first is that the nugget magnetic field induces an electric field due to the axion wall, which may induce pair production by Schwinger effect. Depending on the value of the magnetic field, the pair production can be quite large. A critical value for such magnetic field at the surface of the nugget is obtained, and it is argued that the value of the magnetic field of Tatsumi (2000) is at the verge of stability and may induce large pair production. The consequences of this enhanced pair production may be unclear. It may indicate that the the nugget evaporates, but on the other hand it may be just an indication that the intrinsic magnetic field disappears and the nuggets evolves to a non magnetized state such as in Zhitnitsky (2003), Oaknin and Zhitnitsky (Phys. Rev. D 71:023519, 2005), Zhitnitsky (2006), Lawson and Zhitnitsky (2013), Lawson and Zhitnitsky (2017), Liang and Zhitnitsky (2016), Ge et al. (2018), Zhitnitsky (2018), Lawson and Zhitnitsky (2019), Raza et al. (2018), Fischer et al. (2018), van Waerbeke and Zhitnitsky (2019), Flambaum and Zhitnitsky (2019), Lawson and Zhitnitsky (2017), and Ge et al. (2019). The interaction of such magnetic and electric nugget with the troposphere of the earth is also analyzed. It is suggested that the cross section with the troposphere is enhanced in comparison with a non magnetic nugget but still, it does not violate the dark matter collision bounds. Consequently, these nuggets may be detected by impacts on water or by holes in the mountain craters (Pace VanDevender et al. in Sci Rep 7:8758, 2017). However, if the magnetic field does not decay before the actual universe, then this would lead to high energy electron flux due to its interaction with the electron gases of the Milky Way. This suggests that these magnetized quarks may be a considerably part of dark matter, but only if their hypothetical magnetic and electric fields are evaporated.

ЕКСПЕРИМЕНТАЛЬНЕ ДОСЛІДЖЕННЯ ХАРАКТЕРИСТИК ФОТООПОРІВ

The article describes the experimental study of the basic characteristics and parameters of semiconductor photo resistances by students of physics at the Pedagogical University. The study was conducted at a laboratory stand developed, patented and manufactured by us. One of the main components of the professional training of future physics teachers is the formation of skills for organizing and conducting a physical experiment, among them acquiring new knowledge; forming the primary skills of using physical equipment and devices; acquiring the ability to plan the experiment and analyze the results. Our studies have shown that performing only laboratory work according to the prepared instructions, do not yet provide adequate preparation for independent planning and conducting experimental research by students. In order to partially solve the problem of improvement the forms and methods of organizing the initial experiment, we have proposed a pilot work that can be done in the final stage of specialist training. The purpose of the article is to analyze the results of the study of the photographic resistance characteristics that was offered to students. Studies in which was used photoresist, based on sulfur cadmium included: taking of current voltage, light, spectral and frequency characteristics of photo-resists; determination of integral sensitivity of photo-resistance; determining the influence of external factors on the characteristics of semiconductors. Students studied photographic resistance before and after treatment of its working surface with high-energy electron fluxes with a maximum energy of up to 1.15 MeV to identify the influence of external factors on the characteristics and parameters of semiconductors. The semiconductor was irradiated with electrons on an industrial electron accelerator. Involvement of students in experimental work conducted during extracurricular time and under the guidance of the teacher is essential in generalizing generic experimental research skills of future specialists. Key words: physical experiment, semiconductor, photo-resistance, properties.

Characterization of transient signal induced in IR detector array by Jupiter high-energy electrons and implications for JUICE/MAJIS operability

MAJIS is the visible-infrared spectral imager of the JUICE mission, scheduled by ESA to explore Jupiter and its three icy Galilean moons starting in 2030. It will encounter a challenging environment, the intense Jovian magnetosphere, which among the various expected effects of radiation on detector operability, raises the major issue of transient signal perturbations generated by electrons during every acquisition. This paper aims at a precise characterization of the consequences of such a flux of high-energy electrons on MAJIS detectors in order to evaluate their impact on their operability.To assess the effects of this environment on MAJIS during the mission, we exposed two candidate detectors for the mission to β− radioactive sources simulating an environment around the ~ MeV energy. The candidate detectors under tests were Teledyne H1RG and SOFRADIR Retina NGP MWIR with 5.3 μm cut-off. We have developped and validated an algorithm to interpret these measurements and characterize the distribution of electron impacts (or “spikes”) both in terms of intensity and spatial distribution.The main trends we identify are that the Sofradir detector generates in average 1 spike per electron while the H1RG generates in average 2 spikes per electron forming a spatial cluster. The counterpart that we observe is that more energy is deposited in single spikes on the Sofradir than on the H1RG. Yet, the transient signals are of the order of magnitude of 1000 charges in average, filling less than 1% of the full-well capacity of both detectors. Since the foreseen strategy to discriminate the spikes is time filtering on acquisitions that will be split into sub-integrations, the absence of time persistence of the spike signal was paramount and we managed to check its absence on both detectors. We conclude that the expected effects on operability should be effectively mitigated by the foreseen despiking strategy.

Numerical and Experimental Characterizations of Currents and Magnetic Fields Produced by Electrostatic Discharges Within Dielectrics Irradiated by High-Energy Electron Flux

Electron-caused electromagnetic pulse (ECEMP) is susceptible to occur into constitutive dielectrics of satellites during their mission due to natural space ionizing environment. This paper reports the numerical and experimental characterizations of the electromagnetic fields subsequently generated by the electrostatic discharges (ESDs) from the analysis of the resonant cavity modes and the replacement currents. ESDs are produced when the polytetrafluoroethylene (PTFE or Teflon) samples are irradiated by a 6-MeV electron beam generated by the linear accelerator (LINAC) facility. The measured electromagnetic fields and currents are reproduced by a parametric analysis based on the 3-D Maxwell solution. Such a reproduction of the measured currents and magnetic fields allowed us to quantify the temporal and spectral characteristics of the ESD. It is shown that ESD is produced by bulk currents in the dielectric composed by a fast contribution (rise time lower than 100 ps) and a slower one (of about 200-ns duration).

Internal Charging Issues Met During Electric Orbit Raising and in GPS-Like MEO Environment

This paper was dedicated to the experimental characterization and numerical assessment of the possible risk of charging during the electric orbit raising (EOR). Different elements [printed circuit board (PCB), ethylene tetrafluoroethylene wires (ETFE)] considered at risk in representative electron environment have been tested to assess their charging behavior and any risks of electrostatic discharges in this environment. This task has been performed in the GEODUR irradiation test facility installed at Office National d’Etudes et de Recherches Aerospatiales (Toulouse, France) and equipped with a 2.5-MeV electron accelerator. The samples have been irradiated with an electron spectrum representative of the maximum spectrum (in regard of electron flux) met during the EOR behind 1-mm shielding. This experimental study revealed high charging kinetics on the different elements over successive cycles that led to the initiation of several electrostatic discharges on PCB, located on metallic floating parts. This paper demonstrated the risk of high charging and electrostatic discharge (ESD) risks during EOR on sensitive components. These discharges could affect the electronics operation and damage the insulators. The final step of this paper was to perform numerical simulation for internal charging assessment in global positioning system (GPS)-type orbit on different space used materials with a dedicated tool that takes into account the temporal evolution of high energy electron fluxes. Then we demonstrated a strong evolution of internal charging with the radiation environment, which has been ascribed to the influence of radiation-induced conductivity (RIC). Strong discrepancies from one material to the other have been observed later on the temporal evolution of the surface potential.

Simulations of hybrid direct current radiofrequency (dc/rf) capacitively coupled plasmas

Effects of applying a high negative direct current (dc) voltage in argon capacitive coupled plasmas on the flux of secondary electrons (SEs) to a radiofrequency (rf) biased electrode and plasma uniformity were investigated using particle-in-cell Monte Carlo collision simulation and results were compared with experimental results. High energy SEs originating at electrodes with high negative dc voltage due to ion-impact as well as electron-impact were accelerated out of the sheath through the sheath voltage drop. These SEs gain energy equal to the applied dc voltage and either travel to the wafer electrode where they are lost (dumped) or are trapped between electrodes depending on the voltage on bottom electrode. Trapping and dumping of ballistic electrons depends on the magnitudes of the voltages (dc and rf) applied to each electrode. High energy SEs alter the electron energy distribution function at the wafer, high energy electron flux to the wafer and the plasma density profile. With the application of negative dc voltage, wafer receives high energy electron flux with energies up to applied dc voltage. For the range of conditions examined in this paper, the plasma density increases with the application of the negative dc voltage due to ionization by trapping of high energy SEs. The electrons that originate at the negative dc electrode minimize the impact of enhanced radial electric fields at the rf electrode edge allowing dc/rf plasmas to be center peaked even at low (13.56 MHz) rf frequencies.

The Destruction of Carbon Tetrachloride Dissolved in Water in a Dielectric Barrier Discharge in Oxygen

The kinetics of decomposition of tetrachloromethane (TCM) in its aqueous solutions and the kinetics of decomposition products formation was investigated under the action of DBD at atmospheric pressure in oxygen in a falling-flow reactor. The range of initial concentrations of TCM was 25–325 μmol/l, the discharge power—2–11 W and O2 flow rates—1–3 cm3/s. It is shown that the kinetics of the TCM decomposition can be described by the equation of pseudo-first kinetic order. The rate constant depended weakly on the discharge parameters and was ~ 5 s−1. The energy efficiency of the decomposition, depending on the parameters, was 0.1–1.3 molecules per 100 eV. When the residence time of the solution with the discharge zone is more than 1 s, it is possible to achieve almost 100% degree of TCM decomposition. It is shown that the main products of the TCM decomposition in the liquid phase are aldehydes and Cl− ions, and in the gas phase—the molecules CO and CO2. The results for energy efficiency are compared with the results obtained in other AOP’s processes (Fenton process, photocatalytic process, the radiation process by the action of high-energy electron flux). It is shown that the action of the DBD is more effective than the action of the above processes.

Time evolution of stimulated Raman scattering and two-plasmon decay at laser intensities relevant for shock ignition in a hot plasma

Laser–plasma interaction (LPI) at intensities $10^{15}{-}10^{16}~\text{W}\cdot \text{cm}^{-2}$ is dominated by parametric instabilities which can be responsible for a significant amount of non-collisional absorption and generate large fluxes of high-energy nonthermal electrons. Such a regime is of paramount importance for inertial confinement fusion (ICF) and in particular for the shock ignition scheme. In this paper we report on an experiment carried out at the Prague Asterix Laser System (PALS) facility to investigate the extent and time history of stimulated Raman scattering (SRS) and two-plasmon decay (TPD) instabilities, driven by the interaction of an infrared laser pulse at an intensity ${\sim}1.2\times 10^{16}~\text{W}\cdot \text{cm}^{-2}$ with a ${\sim}100~\unicode[STIX]{x03BC}\text{m}$ scalelength plasma produced from irradiation of a flat plastic target. The laser pulse duration (300 ps) and the high value of plasma temperature ( ${\sim}4~\text{keV}$ ) expected from hydrodynamic simulations make these results interesting for a deeper understanding of LPI in shock ignition conditions. Experimental results show that absolute TPD/SRS, driven at a quarter of the critical density, and convective SRS, driven at lower plasma densities, are well separated in time, with absolute instabilities driven at early times of interaction and convective backward SRS emerging at the laser peak and persisting all over the tail of the pulse. Side-scattering SRS, driven at low plasma densities, is also clearly observed. Experimental results are compared to fully kinetic large-scale, two-dimensional simulations. Particle-in-cell results, beyond reproducing the framework delineated by the experimental measurements, reveal the importance of filamentation instability in ruling the onset of SRS and stimulated Brillouin scattering instabilities and confirm the crucial role of collisionless absorption in the LPI energy balance.

The Effect of the Betatron Mechanism on the Dynamics of Superthermal Electron Fluxes within Dipolizations in the Magnetotail

The dynamics of high-energy electron fluxes (with energies over 40 keV) is analyzed in 13 events of magnetic field dipolization observed by the Cluster satellites in the near-tail of the Earth magnetosphere. In all of the events, the observed energetic electron fluxes are enhanced simultaneously with initial dipolization. Good correlation (correlation coefficient >0.6) is observed between the dynamics of the energetic electron fluxes with energies up to 90 keV and the B-Z component of the magnetic field. Electron fluxes with higher energies display a decline of correlation with the magnetic field. The increase in electron fluxes with energies up to 90 keV during dipolization development is shown to be mainly due to the mechanism of betatron acceleration. The dynamics of electron fluxes with higher energies is poorly described by the betatron scenario and requires consideration of other, probably nonadiabatic, mechanisms.

DAMPE excess from decaying right-handed neutrino dark matter

The flux of high-energy cosmic-ray electrons plus positrons recently measured by the DArk Matter Particle Explorer (DAMPE) exhibits a tentative peak excess at an energy of around 1.4 TeV. In this paper, we consider the minimal gauged U(1)[Formula: see text] model with a right-handed neutrino (RHN) dark matter (DM) and interpret the DAMPE peak with a late-time decay of the RHN DM into [Formula: see text]. We find that a DM lifetime [Formula: see text] can fit the DAMPE peak with a DM mass [Formula: see text]. This favored lifetime is close to the current bound on it by Fermi-LAT, our decaying RHN DM can be tested, once the measurement of cosmic gamma ray flux is improved. The RHN DM communicates with the Standard Model particles through the U(1)[Formula: see text] gauge boson ([Formula: see text] boson), and its thermal relic abundance is controlled by only three free parameters: [Formula: see text], the U(1)[Formula: see text] gauge coupling [Formula: see text], and the [Formula: see text] boson mass [Formula: see text]. For [Formula: see text], the rest of the parameters are restricted to be [Formula: see text] and [Formula: see text], in order to reproduce the observed DM relic density and to avoid the Landau pole for running [Formula: see text] below the Planck scale. This allowed region will be tested by the search for a [Formula: see text] boson resonance at the future Large Hadron Collider.

TeV dark matter and the DAMPE electron excess

The recent high energy electron and positron flux observed by the DAMPE experiment indicates possible excess events near 1.4 TeV. Such an excess may be evidence of dark matter annihilations or decays in a dark matter subhalo that is located close to the solar system. We give here an analysis of this excess from annihilations of Dirac fermion dark matter which is charged under a new $U(1)_X$ gauge symmetry. The interactions between dark matter and the standard model particles are mediated the $U(1)_X$ gauge boson. We show that dark matter annihilations from a local subhalo can explain the excess with the canonical thermal annihilation cross section. We further discuss the constraints from the relic density, from the dark matter direct detection, from the dark matter indirect detection, from the cosmic microwave background, and from the particle colliders.

Radiation Effects and Optical Properties of Aluminoborosilicate Glass Doped with RE Ions

The relationship between the oxidation-reduction state of rare-earth (RE) elements (Sm, Gd, Eu, Ce, Nd), optical properties and the structural evolution of aluminoborosilicate glasses is studied. The study of the optical characteristics of glass is carried out by measuring optical transmission and analyzing Raman spectra. It is found that the increase in the concentration of monovalent Nd ions leads to the broadening of the optical band of forbidden energies (the band gap Eg), while the larger content of multivalent Sm, Eu, and Ce ions significantly decreases its width. The narrowing of Eg results from the irradiation of glass with a high-energy electron flux (2.5 MeV, a dose of up to 109 Gy). The observed evolution is explained by the coexistence of different charge states and the local environments of RE ions in the studied glass. The presence of different charge states of RE ions causes an increase in the number of color centers, while variations in the local environment of ions change the amount of nonbridging oxygen in the structure.

Relativistic electrons of the outer radiation belt and methods of their forecast (review)

The paper reviews studies of the dynamics of relativistic electrons in the geosynchronous region. It lists the physical processes that lead to the acceleration of electrons filling the outer radiation belt. As one of the space weather factors, high-energy electron fluxes pose a serious threat to the operation of satellite equipment in one of the most populated orbital regions. Necessity is emphasized for efforts to develop methods of forecasting the situation in this part of the magneto-sphere, possible predictors are listed, and their classifi-cation is given. An example of a predictive model for forecasting relativistic electron flux with a lead time of 1–2 days is proposed. Some questions of practical or-ganization of prediction are discussed; the main objec-tives of short-term, medium-term, and long-term fore-casts are listed.

Релятивистские электроны внешнего радиационного пояса и методы их прогноза (обзор)

The paper reviews studies of the dynamics of relativistic electrons in the geosynchronous region. It lists the physical processes that lead to the acceleration of electrons filling the outer radiation belt. As one of the space weather factors, high-energy electron fluxes pose a serious threat to the operation of satellite equipment in one of the most populated orbital regions. Necessity is emphasized for efforts to develop methods of forecasting the situation in this part of the magnetosphere, possible predictors are listed, and their classification is given. An example of a predictive model for forecasting relativistic electron flux with a lead time of 1–2 days is proposed. Some questions of practical organization of prediction are discussed; the main objectives of short-term, medium-term, and long-term forecasts are listed.

Magnetospheric Multiscale Observations of Electron Vortex Magnetic Hole in the Turbulent Magnetosheath Plasma

Abstract We report on the observations of an electron vortex magnetic hole corresponding to a new type of coherent structure in the turbulent magnetosheath plasma using the Magnetospheric Multiscale mission data. The magnetic hole is characterized by a magnetic depression, a density peak, a total electron temperature increase (with a parallel temperature decrease but a perpendicular temperature increase), and strong currents carried by the electrons. The current has a dip in the core region and a peak in the outer region of the magnetic hole. The estimated size of the magnetic hole is about 0.23 ρ i (∼30 ρ e) in the quasi-circular cross-section perpendicular to its axis, where ρ i and ρ e are respectively the proton and electron gyroradius. There are no clear enhancements seen in high-energy electron fluxes. However, there is an enhancement in the perpendicular electron fluxes at 90° pitch angle inside the magnetic hole, implying that the electrons are trapped within it. The variations of the electron velocity components V em and V en suggest that an electron vortex is formed by trapping electrons inside the magnetic hole in the cross-section in the M–N plane. These observations demonstrate the existence of a new type of coherent structures behaving as an electron vortex magnetic hole in turbulent space plasmas as predicted by recent kinetic simulations.