Belt Electrons Research Articles

Causal Inference in the Outer Radiation Belt: Evidence for Local Acceleration

AbstractCurrently, there is no clear understanding of the comprehensive set of variables that controls fluxes of relativistic electrons within the outer radiation belt. Herein, the methodology based on causal inference is applied for identification of factors that control fluxes of relativistic electrons in the outer belt. The patterns of interactions between the solar wind, geomagnetic activity and belt electrons have been investigated. We found a significant information transfer from solar wind, geomagnetic activity and fluxes of very low energy electrons (54 keV), into fluxes of relativistic (470 keV) and ultra‐relativistic (2.23 MeV) electrons. We present evidence of a direct causal relationship from relativistic into ultra‐relativistic electrons, which points to a local acceleration mechanism for electrons energization. It is demonstrated that the observed information transfer from low energy electrons at 54 keV into energetic electrons at 470 keV is due to the presence of common external drivers such as substorm activity.

Statistics and Models of the Electron Plasma Density From the Van Allen Probes

AbstractWe use the full NASA Van Allen Probes mission (2012–2019) to extract the electron plasma density from the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) and Electric Field and Waves (EFW) instruments and discuss the evolution of the plasmasphere. We generate new statistics including mean and standard deviations of the plasma density with respect to L‐shell, magnetic local time (MLT), and various geomagnetic indices. These statistics are generated to be applied in radiation belt physics and space weather codes (with fits provided). The mean plasmasphere is circular around Earth with respect to MLT for Kp < 1. The mean 100 cm−3 level line is above L = 5 and mean 10 cm−3 level expands above the Van Allen Probes apogee for Kp < 1. The outer electron belt lies within the plasmasphere for 60% of all times. As activity increases (Kp > 2), a gradual MLT asymmetry forms with higher mean density in the afternoon sector due to plumes expanding outward. Conversely, the mean density decreases on the dawn and night sectors. The mean density is between ∼500 and ∼50 cm−3 between L ∼ 4 and L ∼ 6 during quiet and moderately active times (Kp < 3), representing ∼80% of all times. Statistics in regions of high density below L = 2 are underdefined for intense activity. The highest standard deviation of density represents a factor 2.5 to 3 times the mean above L = 5 and for active times. We find the percent difference between the EFW and EMFISIS densities is bounded by ±20% for quiet and moderate activity (Kp < 5) and goes up to ±100% for extreme activity.

Statistical Analysis of the Differential Deep Penetration of Energetic Electrons and Protons into the Low L Region (L < 4)

AbstractDeep penetration of energetic electrons (10s–100s of keV) to low L‐shells (L < 4), as an important source of inner belt electrons, is commonly observed during geomagnetically active times. However, such deep penetration is not observed as frequently for similar energy protons, for which underlying mechanisms are not fully understood. To study their differential deep penetration, we conducted a statistical analysis using phase space densities (PSDs) of µ = 10–50 MeV/G, K = 0.14 G1/2Re electrons and protons from multiyear Van Allen Probes observations. The results suggest systematic differences in electron and proton deep penetration: electron PSD enhancements at low L‐shells occur more frequently, deeply, and faster than protons. For µ = 10–50 MeV/G electrons, the occurrence rate of deep penetration events (defined as daily‐averaged PSD enhanced by at least a factor of 2 within a day at L < 4) is ∼2–3 events/month. For protons, only ∼1 event/month was observed for µ = 10 MeV/G, and much fewer events were identified for µ > 20 MeV/G. Leveraging dual‐Probe configurations, fast electron deep penetrations at L < 4 are revealed: ∼70% of electron deep penetration events occurred within ∼9 hr; ∼8%–13% occurred even within 3 hr, with lower‐µ electrons penetrating faster than higher‐µ electrons. These results suggest nondiffusive radial transport as the main mechanism of electron deep penetrations. In comparison, proton deep penetration happens at a slower pace. Statistics also show that the electron PSD radial gradient is much steeper than protons prior to deep penetration events, which can be responsible for these differential behaviors of electron and proton deep penetrations.

Specifying High Altitude Electrons Using Low‐Altitude LEO Systems: Updates to the SHELLS Model

Specifying High Altitude Electrons Using Low‐Altitude LEO Systems: Updates to the SHELLS Model

Dynamics of the inner electron radiation belt: A review

The Van Allen radiation belts are an extraordinary science discovery in the Earth magnetosphere and consist of two electron belts. The inner Van Allen belt contains electrons of 10s to 100s keV; the outer belt consists mainly of 0.1−10 MeV electrons. Their dynamics have been analyzed for decades. The newly-launched Van Allen Probes provide unprecedented opportunities to investigate the inner belt more thoroughly. Data from this advanced mission have allowed scientists to demonstrate that the inner belt was formed not only through inward transport of outer belt electrons but Cosmic Ray Albedo Neutron Decay (CRAND) has also played an important role. In addition, the inner belt electrons show energy-dependent variations and present “zebra stripe” structures in the energy spectrum. At the same time, scientists have further confirmed that the electrons in the inner radiation belt get lost through coulomb collision and wave-particle interaction. Despite these advances, important questions remain unanswered and require further investigation. The launch of Macau ScienceSatellite-1 mission, with its low inclination angle and low altitude orbit, will provide advanced radiation belt data for better understanding of the structure and dynamics of the inner electron radiation belt.

Intense chorus waves are the cause of flux-limiting in the heart of the outer radiation belt

Chorus waves play a key role in outer Van Allen electron belt dynamics through cyclotron resonance. Here, we use Van Allen Probes data to reveal a new and distinct population of intense chorus waves excited in the heart of the radiation belt during the main phase of geomagnetic storms. The power of the waves is typically ~ 2–3 orders of magnitude greater than pre-storm levels, and are generated when fluxes of ~ 10–100 keV electrons approach or exceed the Kennel–Petschek limit. These intense chorus waves rapidly scatter electrons into the loss cone, capping the electron flux to a value close to the limit predicted by Kennel and Petschek over 50 years ago. Our results are crucial for understanding the limits to radiation belt fluxes, with accurate models likely requiring the inclusion of this chorus wave-driven flux-limiting process, that is independent of the acceleration mechanism or source responsible for enhancing the flux.

Detection of the third innermost radiation belt on LEO CORONAS-Photon satellite around 2009 solar minimum

We analyze variations of high energy charged particle populations filling various magnetospheric regions under, inside and outside of the Van Allen inner and outer electron radiation belts in May 2009. The study is based on the experimental data obtained from the STEP-F and the SphinX instruments placed close to each other aboard the low-Earth circular orbit CORONAS–Photon satellite. Data analysis of particle fluencies collected from the highly sensitive STEP-F device indicates the presence of a persistent electron belt at L ≈ 1.6, i.e., beneath the well-known Van Allen electron inner radiation belt of the Earth’s magnetosphere. The electron energy spectrum in this “new” belt is much steeper than that of the inner belt, so that the electrons with energies Ee ≥ 400 keV were almost not recorded on L ≈ 1.6 outside the South Atlantic Anomaly (SAA). We introduce the concept of effective lowest threshold energies for X-ray detectors used in the solar soft X-ray spectrophotometer SphinX and define their values for two regions: the SAA and in the Van Allen outer belt. Different values of lowest threshold energies are directly associated with different slopes of particle energy spectra. Cross-analyses of data obtained from the STEP-F and SphinX instruments initially built for various purposes made it possible to detect the highly anisotropic character of the spatial electron distribution in radiation belts in both Southern and Northern hemispheres. We detected also the presence of low-energy electrons at all latitudes during the main phase of a weak geomagnetic storm.

Mill Feed Control System and Algorithm Based on Python

Grinding is an important link in the process of mineral processing. It plays a vital role in mineral processing by optimizing the grinding process, improving the quality of grinding products and ensuring the follow-up operation indicators. In this paper, the Python language, intelligent theoretical control technology and mineral processing were combined to solve the problem of ore feeding control in mineral processing. Using error factor analysis, an extended control algorithm was designed. The NumPy library and data collected from the Yuan YangMou concentrator in China were used to quantitatively analyze the factors affecting the error of electronic belt scales. This paper introduces the use of Kalman filtering for electronic belt scale weight data to reduce the effect of noise and hence reduce errors. The factors affecting the process of mill feeding are also analyzed. The core ideas and methods of fuzzy control theory are summarized, and a Python-based fuzzy controller suitable for the mill feeding process that improves the overall robustness and accuracy of feeding system is implemented.

DIME-2 Flown as Part of NASA’s SET-1 on the DSX Satellite

The objective of the Dosimetry Inter-comparison and Miniaturization Experiment (DIME) approach is to compare different miniature electronic dosimeters for monitoring exposure to ionizing radiation primarily in terms of potential degradation due to total ionizing dose (TID) and the threat of single event effects (SEEs). As the title implies, DIME is divided in two parts: DIME-1 is a passive board that is turned on only to read the cumulative dose and DIME-2 is an active board that requires continuous power to monitor the radiation-induced energy depositions that can lead to SEE. This article describes the details of the operation of DIME-2 and the results of the flight on the Demonstration and Science Experiments (DSX) satellite which orbited the Earth in an elliptical middle earth orbit (MEO) orbit that extended from 6000 to 12 000 km at an inclination of 42° thereby crossing the entire slot region between the inner and outer electron belts. Measurements made every 15 min consistently showed a large peak in the energy depositions at perigee and a small one near apogee with fewer events in the slot region.

On the Challenges of Measuring Energetic Particles in the Inner Belt: A Geant4 Simulation of an Energetic Particle Detector Instrument, REPTile‐2

AbstractFollowing the retirement of the community supported Van Allen Probes mission, the quest for high‐quality energetic particle measurements in the radiation belts is likely to be taken on by smaller spacecraft like CubeSats in the foreseeable future. Here we introduce the Relativistic Electron Proton Telescope integrated little experiment‐2 (REPTile‐2), a miniaturized (∼1.5 U) solid‐state charged particle telescope that aims to undertake this challenging task. It incorporates detailed pulse‐height analysis to enable 60 electron channels and 60 proton channels and includes anticoincidence detectors to minimize unwanted background contamination. This paper presents a description of the REPTile‐2 design and emphasizes the importance of extensive Geant4‐based analysis to inform the design of a new energetic particle detector and characterize the instrument response. Our analysis shows that REPTile‐2 can measure ∼0.3–∼4 MeV electrons and ∼6.7–35 MeV protons with energy resolution (∆E/E) of 7%–38% for electrons and 1.5%–5% for protons. Results from a Sr‐90/Y‐90 radioactive source test have verified the instrument performance and the validity of the Geant4 simulations. These energetic particle measurements will enable a new scientific understanding of the inner radiation belt, where unwanted contamination from the unforgiving penetration of highly energetic protons (tens of MeV to GeV) is common, and provide detailed quantification of the inner belt electrons and protons in the low‐Earth orbit that is crucial for space weather modeling.

The Origin of the Unfocused XMM-Newton Background, Its Variability, and Lessons Learned for ATHENA

Abstract We analyzed the unexposed to the sky (outFOV) region of the MOS2 detector on board XMM-Newton covering 15 yr of data amounting to 255 Ms. We show convincing evidence that the origin of the unfocused background in XMM-Newton is due to energetic protons, electrons, and hard X-ray photons. Galactic cosmic rays are the main contributors as shown by the tight correlation (2.6% of total scatter) with the 1 GeV proton data of the SOHO EPHIN detector. Tight correlations are found with a proxy of the Chandra background rate, revealing the common source of background for detectors in similar orbits, and with the data of the EPIC Radiation Monitor, only when excluding Solar energetic particle events. The entrance to the outer electron belts is associated with a sudden increase in the outFOV MOS2 rate and a spectral change. These facts support the fact that MeV electrons can generate an unfocused background signal. The correlation between MOS2 outFOV data and the SOHO EPHIN data reveals a term constant in time and isotropic, similar to the one found in the study of the pn data. The most plausible origin of this component is hard unfocused X-ray photons of the cosmic X-ray background Compton scattering in the detector as supported by the strength of the signal in the two detectors with different thicknesses. Based on this physical understanding, a particle radiation monitor on board the Advanced Telescope for High Energy Astrophysics has been proposed and it is currently under study. It will be able to track different species with the necessary accuracy and precision to guarantee the challenging requirement of 2% reproducibility of the background.

Application of Materials in Radiation Hardening

Radiation shielding is an imperative as radiation can be serious concern within in such environment, where this environment can be either natural or man-made. The natural radiation source like solar wind that is consisting of Electron, Gamma, Protons, Neutrons, or Van Allen Belt, etc. while, the source of man-made is nuclear power facilities or either Exo- tmospheric or Endo-Atmospheric nuclear explosion. The effects of nuclear explosions produce both immediate and delayed destructive effects, that requires choice of right and proper protective materials for ICs to be shielded and survivable in such radiation environment driven by a nuclear weapon burst. Nuclear weapon effects in term of blast, thermal radiation, electromagnetic pulse, and prompt ionizing radiation, etc. are part of concerns for choosing the proper materials. Radiation shielding is based on the principle of attenuation, which is the ability to reduce a waves or ray’s effect by blocking or bouncing particles through a barrier material. This short review is discussing different holistic issues in respect to selected materials and integrated circuits in respect to survivability and shielding within a radiation environment, either man-made or natural.

Dynamic Coal Quantity Detection and Classification of Permanent Magnet Direct Drive Belt Conveyor Based on Machine Vision and Deep Learning

Real-time and accurate measurement of coal quantity is the key to energy-saving and speed regulation of belt conveyor. The electronic belt scale and the nuclear scale are the commonly used methods for detecting coal quantity. However, the electronic belt scale uses contact measurement with low measurement accuracy and a large error range. Although nuclear detection methods have high accuracy, they have huge potential safety hazards due to radiation. Due to the above reasons, this paper presents a method of coal quantity detection and classification based on machine vision and deep learning. This method uses an industrial camera to collect the dynamic coal quantity images of the conveyor belt irradiated by the laser transmitter. After preprocessing, skeleton extraction, laser line thinning, disconnection connection, image fusion, and filling, the collected images are processed to obtain coal flow cross-sectional images. According to the cross-sectional area and the belt speed of the belt conveyor, the coal volume per unit time is obtained, and the dynamic coal quantity detection is realized. On this basis, in order to realize the dynamic classification of coal quantity, the coal flow cross-section images corresponding to different coal quantities are divided into coal type images to establish the coal quantity data set. Then, a Dense-VGG network for dynamic coal classification is established by the VGG16 network. After the network training is completed, the dynamic classification performance of the method is verified through the experimental platform. The experimental results show that the classification accuracy reaches 94.34%, and the processing time of a single frame image is 0.270[Formula: see text]s.

The Characteristics of Three‐Belt Structure of Sub‐MeV Electrons in the Radiation Belts

AbstractAfter the launch of Van Allen Probes, the three‐belt structures of ultra‐relativistic electrons are discovered. In this study, we investigate the three‐belt structures of sub‐MeV electrons, which may form under different mechanism compared with those of ultra‐relativistic electrons and are worth in‐depth analysis. Based on the differential flux data from Magnetic Electron Ion Spectrometer onboard Radiation Belt Storm Probes‐B satellite, we find 54 events, in which two comparable peaks of sub‐MeV electron fluxes and a slot appear where there should be the outer radiation belt. Through the statistical analysis, the three‐belt structures of sub‐MeV electrons are found to be closely related to symmetric H‐component (SYM‐H) and Auroral Electrojet (AE) indices. The 2‐day SYM‐H minimum and AE maximum before the event have a linear trend with the remnant belt and the “second slot” locations. The L‐values of the remnant belt and the “second slot” of different energy electrons decrease as energy increases in general and show interesting characteristics during their temporal evolution. Moreover, the lifetime of the remnant belt of different energy electrons increases as energy increases. We find similarities and differences between sub‐MeV and ultra‐relativistic electrons three‐belt events, which provides a new perspective in three‐belt structure study.

High Latitude Zones of GeV Heavy Ions at the Inner Edge of Jupiter's Relativistic Electron Belt

AbstractJuno has discovered signatures of a high energy heavy ion population (>100 MeV/nucleon) within the inner edge of Jupiter's relativistic electron belt. The particles were detected in narrow zones in the high‐latitude lobes of the synchrotron emission region, a location never explored by prior spacecraft (∼31°–46° magnetic latitude; radial distances 1.12–1.41 Jovian radii, M‐shells 1.5–2.37). The population was revealed by extremely high signal ionization signatures seen in images collected by Juno's Stellar Reference Unit star camera (equivalent to 0.2–0.7 MeV of deposited energy per pixel). Signature morphology indicates a population of GeV ions (Z > 1) with atomic mass as high as sulfur, although species with 2 ≤ Z ≤ 8 potentially account for all of the signatures. The detections have occurred while the spacecraft is magnetically connected to Jupiter's halo and gossamer rings, but not while it is connected to the main ring; similar to equatorial observations of GeV carbon and sulfur ions by the Galileo Probe. We find that the particles reside on magnetic drift shells that suggest they are stably trapped within Jupiter's magnetosphere. Because the cosmic ray albedo neutron decay mechanism can only produce protons and electrons, it cannot be the source of this trapped Z > 1 ion population; other galactic cosmic ray origins are suspected. Inward radial transport of tens of keV heavy ions from the outer magnetosphere is another potential source.

Statistical Distribution of Bifurcation of Earth's Inner Energetic Electron Belt at Tens of keV

AbstractWe present a survey of the bifurcation of the Earth's energetic electron belt (tens of keV) using 6‐year measurements from Van Allen Probes. The inner energetic electron belt usually presents one‐peak radial structure with high flux intensity at L < ∼2.5, which however can be bifurcated to exhibit a double‐peak radial structure. By automatically identifying the events of bifurcation based on Radiation Belt Storm Probes Ion Composition Experiment data, we find that the bifurcation is mostly observed at ∼30–100 keV with a local flux minimum at L = ∼2.0 to ∼2.3 under relatively quiet geomagnetic conditions, typically after a significant flux enhancement due to radial diffusion or injections to L < ∼2.5. The bifurcation typically lasts for a few days during quiet periods until interrupted by injections or radial diffusion. The L‐shell, energy, and seasonal dependences of the occurrence of bifurcated inner electron belt support the important role of electron scattering by very low‐frequency transmitter waves in the bifurcation formation.

Networked high-precision and high-stability array electronic belt scale instrument

Networked high-precision and high-stability array electronic belt scale instrument

Very-Low-Frequency transmitters bifurcate energetic electron belt in near-earth space

Very-Low-Frequency (VLF) transmitters operate worldwide mostly at frequencies of 10–30 kilohertz for submarine communications. While it has been of intense scientific interest and practical importance to understand whether VLF transmitters can affect the natural environment of charged energetic particles, for decades there remained little direct observational evidence that revealed the effects of these VLF transmitters in geospace. Here we report a radially bifurcated electron belt formation at energies of tens of kiloelectron volts (keV) at altitudes of ~0.8–1.5 Earth radii on timescales over 10 days. Using Fokker-Planck diffusion simulations, we provide quantitative evidence that VLF transmitter emissions that leak from the Earth-ionosphere waveguide are primarily responsible for bifurcating the energetic electron belt, which typically exhibits a single-peak radial structure in near-Earth space. Since energetic electrons pose a potential danger to satellite operations, our findings demonstrate the feasibility of mitigation of natural particle radiation environment.

Sustaining Saturn's Electron Radiation Belts Through Episodic, Global‐Scale Relativistic Electron Flux Enhancements

AbstractThe L shell distributions of MeV electrons in Saturn's radiation belt are investigated orbit by orbit for the 13‐year exploration of Cassini. It is found that in addition to the monotonic decrease profiles, there are orbits showing superimposed transient extensions. The extensions are found to stand out above the background population during 50% of belt crossings. We estimate that there is high probability (>72%) that transient extensions contribute more than 10% electron content in the radiation belt. The high occurrence frequency of one extension every 2–3 weeks, together with the relative content, demonstrate that the extensions constitute a regular and fundamental process populating and sustaining the electron belts of Saturn. The transients regularity excludes interplanetary coronal mass ejections as dominant trigger and implies corotation interaction regions and/or internal processes as candidates. Statistical results suggest that the communication of electrons between the middle magnetosphere and the radiation belts is largely through convective radial transport, which produces transient radiation belt extensions.

Charging Monitor Aboard the Geostationary Satellite GK2A at 128.2° E Longitude

A simple internal charging current monitor has been developed to monitor the penetration of energetic particles within spacecraft in geostationary orbits. The instrument, known as a charging monitor (CM), is a component of a suite of space weather instruments aboard the geostationary satellite GEO-KOMPSAT-2A (GK2A), that was successfully launched on December 4, 2018, with a final longitude of 128.2° E. The instrument measures the integral fluxes of charged particles through a 1-mm-thick aluminum wall, along with another 1-mm-thick aluminum plate, effectively collecting electron and proton currents with energies approximately above 0.6 and 13.1 MeV, respectively. Great care has been exercised in the design of the instrument to extend the lifetime of the analog electronics of the detector, which may easily become vulnerable to the harsh radiation environment of the outer electron belt in geostationary orbits. Comparisons of measurements from the CM have been made with those from particle detectors with a more sophisticated design from the same suite. Initial results of the CM operation for the first four months are presented, including a period of moderate geomagnetic storms. The comparisons clearly show that the CM is sufficiently capable of monitoring the enhanced levels of electrical currents from the penetration of high-energy charged particles in the context of space weather research with a minimal spacecraft resources cost and design efforts.