Artificial Radiation Belt Research Articles

Radiation-Induced Dark Counts for Silicon Single-Photon Detectors in Space

Single-photon detectors operating on satellites for use in a quantum communications network can incur large dark-count-rate increases from the natural radiation environment of space. Displacement damage to the material lattice of a detector from the ionizing radiation can result in a permanent dark-count increase in the detector. In this work, we analyze the radiation-induced dark-count rate of a silicon single-photon avalanche diode onboard a satellite at different orbiting altitudes, as well as, the additional radiation from a nuclear-disturbed environment caused by a high-altitude nuclear explosion. For detectors on low Earth orbit satellites, protons are the biggest source of radiation damage and are best mitigated by choosing an orbit that minimizes exposure when passing through the South Atlantic Anomaly and Polar Cusps. Detectors on medium Earth orbit and geostationary orbit satellites, if shielded by more than 10 mm of aluminum, provide the best platform in terms of the least amount of radiation damage to the detectors. In the event of a high-altitude nuclear explosion, the artificial radiation belts produced by the explosion will cause too much damage to silicon single-photon detectors on low Earth orbit satellites and render them unfit for quantum communications in less than a day. Higher orbit satellites will only suffer minor dark-count-rate increases from the artificial radiation belts.

Simulations of Internal Charging Effects of Artificial Radiation Belt on Dielectric Material

To find out the law of charging effects of high-energy electrons in artificial radiation belt produced by a high-altitude nuclear explosion (HANE) on the dielectric materials, we present a simulation model of high-energy electrons in artificial radiation belt contributing to internal charging of dielectric material, which are commonly used inside the satellites or spacecraft. The deposition electric parameters such as injection current density, charge deposition rate, and radiation dose rate are obtained by using the Monte Carlo simulation method. The equations of charging electric field of Teflon material have been presented and numerically solved. The distributions of electric field and potential in the dielectric material Teflon charged by artificial radiation belt and the change rules with charging time have been obtained. The results show that the peak charging electric field produced by artificial radiation belt in dielectric material is lower than that produced by 1-MeV single-energy electron under the same injection current density. When the artificial radiation belt generated by the HANE with a yield of 5 kt charges the Teflon material with a thickness of 4 mm, the time needed for charging to reach saturation will be more than 24 h, and the saturated charging electric field can reach 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> V/m, so the discharge risk is low. For artificial radiation belt generated by the HANE with a yield 1.4 Mt, when the time to start charging is within 100 days after the explosion and the charging duration is within 1 h, the maximum charging electric field in Teflon material will exceed 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> V/m and the discharge risk will be high.

Sky-distribution of intensity of synchrotron radio emission of relativistic electrons trapped in Earth’s magnetic field

This paper presents the calculations of synchrotron radio emission intensity from Van Allen belts with Gaussian space distribution of electron density across L-shells of a dipole magnetic field, and with Maxwell’s relativistic electron energy distribution. The results of these calculations come to a good agreement with measurements of the synchrotron emission intensity of the artificial radiation belt’s electrons during the Starfish nuclear test. We have obtained two-dimensional distributions of radio brightness in azimuth — zenith angle coordinates for an observer on Earth’s surface. The westside and eastside intensity maxima exceed several times the maximum level of emission in the meridian plane. We have also constructed two-dimensional distributions of the radio emission intensity in decibels related to the background galactic radio noise level. Isotropic fluxes of relativistic electrons (E ~ 1 MeV) should be more than 107 cm–2s–1 for the synchrotron emission intensity in the meridian plane to exceed the cosmic noise level by 0.1 dB (riometer sensitivity threshold).

О распределении по небесной сфере интенсивности синхротронного радиоизлучения релятивистских электронов, захваченных в магнитном поле Земли

This paper presents the calculations of synchrotron radio emission intensity from Van Allen belts with Gaussian space distribution of electron density across L-shells of a dipole magnetic field, and with Maxwell’s relativistic electron energy distribution. The results of these calculations come to a good agreement with measurements of the synchrotron emission intensity of the artificial radiation belt’s electrons during the Starfish nuclear test. We have obtained two-dimensional distributions of radio brightness in azimuth — zenith angle coordinates for an observer on Earth’s surface. The westside and eastside intensity maxima exceed several times the maximum level of emission in the meridian plane. We have also constructed two-dimensional distributions of the radio emission intensity in decibels related to the background galactic radio noise level. Isotropic fluxes of relativistic electrons (E ~ 1 MeV) should be more than 107 cm–2s–1 for the synchrotron emission intensity in the meridian plane to exceed the cosmic noise level by 0.1 dB (riometer sensitivity threshold).

Development of plasma sources for Dipole Research EXperiment (DREX)

Dipole Research EXperiment (DREX) is a new terrella device as part of the Space Plasma Environment Research Facility (SPERF) for laboratory studies of space physics relevant to the inner magnetospheric plasmas. Adequate plasma sources are very important for DREX to achieve its scientific goals. According to different research requirements, there are two density regimes for DREX. The low density regime will be achieved by an electron cyclotron resonance (ECR) system for the ‘whistler/chorus’ wave investigation, while the high density regime will be achieved by biased cold cathode discharge for the desired ‘Alfvén’ wave study. The parameters of ‘whistler/chorus’ waves and ‘Alfvén’ waves are determined by the scaling law between space and laboratory plasmas in the current device. In this paper, the initial design of these two plasma sources for DREX is described. Focus is placed on the chosen frequency and operation mode of the ECR system which will produce relatively low density ‘artificial radiation belt’ plasmas and the seed electrons, followed by the design of biased cold cathode discharge to generate plasma with high density.

Anthropogenic Space Weather

Anthropogenic effects on the space environment started in the late 19th century and reached their peak in the 1960s when high-altitude nuclear explosions were carried out by the USA and the Soviet Union. These explosions created artificial radiation belts near Earth that resulted in major damages to several satellites. Another, unexpected impact of the high-altitude nuclear tests was the electromagnetic pulse (EMP) that can have devastating effects over a large geographic area (as large as the continental United States). Other anthropogenic impacts on the space environment include chemical release ex- periments, high-frequency wave heating of the ionosphere and the interaction of VLF waves with the radiation belts. This paper reviews the fundamental physical process behind these phenomena and discusses the observations of their impacts.

Numerical simulation of the formation of artificial radiation belt caused by high altitude nuclear detonation

According to the previous theory of the motion of charged particles in the Earths magnetic field， we derive the spatial region to which energetic particles around the Earth can extend. Using an empirical model for radiative debris produced by the high altitude nuclear detonation （HAND），we investigate the primary region where HAND-induced artificial radiation belt can form.Finally，in terms of the fission property of HAND and the characteristic features of energetic electron distributions in the natural belts，the electron flux within the artificial radiation belt is calculated and the preliminary study of its dependences on explosion latitude，altitude，and equivalence are carried out quantitatively. The numerical results show that，under certain circumstances，the HAND with 0.1—1 Mt TNT explosion equivalence can be expected to produce an artificial radiation belt near the Earth with the flux 3—4 orders of magnitude higher than the natural ones. The central location of the artificial belt largely relies on the magnetic latitude where the detonation takes place while the thickness and electron flux of the artificial radiation belt are affected by the explosion altitude and equivalence.

Laboratory Observations of Wave-Induced Radial Transport within an "Artificial Radiation Belt"

Wave-induced radial transport of energetic electrons has been observed in a laboratory terrella. In the experiment, electron-cyclotron-resonance heating (ECRH) is used to create a localized population of trapped energetic electrons (1 keV < E h < 50 keV) within a low-density discharge which we refer to as an artificial radiation belt. As the.intensity of the radiation belt increases, quasiperiodic bursts of drift-resonant fluctuations, ω ≃ ω dh , are excited. The frequency spectrum of this instability is time-varying and complex, and global chaotic radial transport is induced whenever the frequency spectrum is both intense and compact. High-speed measurements of the energetic electron transport are made with particle detectors, and these measurements can be directly compared with nonlinear and self-consistent simulations. We find quasilinear transport simulations do not reproduce the experimental measurements. In contrast, simulations which retain the electron's guiding-center Hamiltonian dynamics and which preserve the first, μ, and second, J, adiabatic invariants reproduce key temporal characteristics of the experimental measurements. The resemblance between simulation and experiment suggests that persistent phase-space structures strongly modulate the energetic electron transport and contribute to the growth and saturation of the instability.

Potential for creation of artificial radiation belts during space testing of an NPB

Because of the potential for the charged effluence from an orbital neutral particle beam (NPB) system to become trapped in the Earth's magnetic field, the creation of long-lived fluxes is possible. The circumstances that can lead to trapping of protons from an H/sup 0/ NPB system operated at altitudes of 300-1000 km are considered. A first-order assessment of the flux levels and decay rates of the relic protons produced is presented. An NPB could significantly enhance the near-Earth radiation environment for up to several years, and as such could contributed to the radiation hazard.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Energetic charged particle and electromagnetic wave injections into space

Man’s first, and most dramatic, activities in this field were to conduct high altitude (400...500 kin) nuclear explosions in the late 1950s and early 1960s. The Argus experiment created charged particles which affected the Van Allen trapped radiation belts. The Starfish experiment of 9 July 1962 had. a higher yield (l.L~Megaton (Mt)) than the Argus explosions (~1 kt); an intense artificial radiation belt was created, and this lasted longer (many years) since the source was at a lower latitude (Johnson Island, Pacific Ocean) than that used for the earlier Argus shots (South Atlantic). Three Soviet explosions in October and November 1962 made artificial radiation belts which were less intense than that due to Starfi~h. Because their source was at a higher latitude (Siberia) these belts decayed rather rapidly. Interesting effects have been observed in the VLF and ELF radio bands after high—altitude nuclear explosions. At the instant of detonation of Starfish, electromagnetic signals were radiated; a whistler was received in the opposite hemisphere. Only seconds after the explosion, artificial aurorae were observed in New Zealand and the absorption of cosmic radio noise by the Alaskan ionosphere was increased. The peak absorption occurred within one minute, with recovery to normal conditions taking a few hours. After a few minutes the ionosonde in Jamaica indicated greater absorption in the lower ionosphere. Also some minutes after the explosion the Q value of the resonant (8 Hz) earth-ionosphere cavity decreased; after about three hours it returned to its normal value. The change may be explained, not only by the enhancement of ionisation below the explosion, but also by the world—wide (low-latitude) ionisation produced by the trapped energetic electrons, arising from neutron decay, drifting eastwards in longitude. Synchrotron radiation from the ~ 2 million electron volt (MeV) electrons produced by the explosion was detected by radioastronomy observatories at low latitudes.

Radial diffusion of electrons at lowLvalues

Unique solution for radial diffusion coefficient applicable to equatorially trapped electrons in artificial radiation belt

Structure and decay of the Starfish radiation belt, October 1963 to December 1965

Structure and decay of artificial radiation belt produced by high altitude nuclear explosion

A charged particle spectrometer for space experimentation

This article presents the design and some test results for a near-earth, satelliteborne solid state detector spectrometer intended to provide useful data on the directionality, spectral intensity, and time fluctuations of the natural and artificial trapped radiation belts, solar flare proton- and alpha emissions, and primary cosmic ray protons and alphas. The objectives of the intended experiment translate into requirements of instrument performance which are concerned with the identification of the particle types in the environment and the simultaneous measurement of the spectral intensity of each, with sufficient directional, time, and energy resolution to allow the data to be related to current models of trapped belt structure and flare proton propagation. The significant performance characteristics of the electronic modules under pulser excitation are described, and the response of the solid state detectors to electrons and protons of various energies is displayed. Particular attention is given to the particle mass and energy resolution achievable with the chosen technique over a wide energy range characteristic of space radiation.

Addition to investigation of the decay of the Starfish Radiation Belt

In a previous paper [Walt, 1964] the observed time variation of the artificial radiation belt produced by the Starfish nuclear explosion was compared with calculations based on the assumption that the electrons were removed by collisions with the ambient atmosphere. It was found that on the magnetic shell L = 1.185, experiment and theory agreed to a remarkable extent. At L = 1.25 the over-all decay rates of theory and experiment were in agreement, but the altitude dependence of the flux was not as expected, the actual flux at low altitude, or high magnetic field B, being greater than the theoretical values. This discrepancy was larger than could be accounted for by possible errors in either the flux measurements or in the atmospheric density and geomagnetic field values used in the calculation.

Effects of a Simulated High-Energy Space Environment on the Ultraviolet Transmittance of Optical Materials between 1050 Å and 3000 Å

Transmittances of LiF, MgF(2), CaF(2), BaF(2), Al(2)O(3), and fused SiO(2)were measured from 1050 A to 3000 A before and after irradiation by 10(14) electrons/cm(2) first at 1.0 MeV and then at 2.0 MeV. Similar measurements were made with 10(14) electrons/cm(2) at 2.0 MeV using A1(2)O(3) to shield fused SiO(2), ADP, calcite, and Corning glass filters 9-54 and 7-54 from the direct electron beam. The electron energy and dose represent what one might expect to encounter in the artificial radiation belt after one year in a circular, near polar orbit at 1400 km. From these measurements it is concluded MgF(2), BaF(2), and A1(2)O(3) have the greatest potential for space applications in the uv.

Very low frequency phase perturbations and the Soviet high-altitude nuclear bursts of October 22 and 28, 1962: 2. Comparison with satellite particle data

Energy and spatial characteristics of artificial radiation belts were deduced in part 1, where we examined the temporal histories of the VLF phase perturbations produced by the two Soviet high-altitude nuclear bursts of October 1962. For both bursts the trapped electrons have energies ≲4 Mev, the electron spectrum ≲0.78 Mev resembling that from the radioactive decay of neutrons. This dichotomy of fission and neutron-decay β particles in the electron spectrum has not been achieved in the satellite particle data so far analyzed, where the energy ranges are either too broad or above 0.78 Mev. For the burst of October 22, the VLF characteristic that electrons ≲4 Mev are trapped in the region encompassing at least 1.75 ≲ L ≲ 3.76 is compatible with the trapped particle flux observed by Explorer 14, Alouette, and Telstar 1. For the burst of October 28, the VLF shows that fission β particles ≳0.78 Mev are not present in L > 2.32 and are confined on shells 1.6 Mev or the Explorer 15 results for electrons >1.9 Mev. The Alouette results also show that the energy spectrum extends to about 10 Mev, but that there is a rapid decrease in flux for E > 4 Mev. For the burst of October 28, the VLF shows that neutron-decay β particles have an outer trapping boundary at 2.32 ≤ L 230 kev but not with the Telstar data for E > 390 kev, where the outer boundary extends to L ∼ 4. The VLF result that protons 2.3 500 kev at L = 2.8 and 3.2. The characteristics of protons from nuclear explosions are reviewed, and the electron results are consolidated to form at least a model for additional investigations of the artificial radiation belts formed by the Soviet bursts of October 22 and 28, 1962.

Comments on "Electron Fluctuations in an Equilibrium Turbulent Plasma''

structural weight is a negligible fraction of the super- conducting weight. Note the correct power dependence of m on V, when the optimization is done at constant current. These weights are lower than those quoted by Bhattacharjie and Michael by a factor of 3 when V = 102, and by a factor of 50 when V = 105. With weights as low as these, it is likely that considerations of the area of cryogenic surface re- quired would exert a significant influence on the design. References 1 Bhattacharjie, A. and Michael, I., Mass and magnetic dipole shielding against electrons of the artificial radiation belt, AIAA J. 2, 2198-2201 (1964). 2 Levy, R. H., shielding of space vehicles by means of superconducti ng coils, ARS J. 31, 1568-1570 (1961). 3 Levy, R. H., Author's reply to Willinski's comment on 'Radi- ation shielding of space vehicles by means of superconducti ng coils/ ARS J. 32, 787 (1962). 4 Levy, R. H., The prospects for active shielding, Pro- ceedings of the Symposium on Protection against Radiation Hazards in Space (Office of Technical Services, Dept. of Commerce, Washington, D. C., 1962), Book 2, pp. 794-807.

Comment on "Mass and Magnetic Dipole Shielding against Electrons of the Artificial Radiation Belt"

Comment on "Mass and Magnetic Dipole Shielding against Electrons of the Artificial Radiation Belt"

Time decay of the artificial radiation belt

Satellite 1963 38C was launched into a nearly circular 1100-km orbit having an inclination of 89.91°. A permanent bar magnet achieved alignment to less than about 5° of the local field direction within five days after launch. The detector used in this study is one of a set of five surface barrier solid state detectors that make up an integral electron spectrometer carried aboard the satellite. The spectrometer is oriented to look out normal to the satellite alignment axis. The detector of interest is sensitive to electrons of Ee ≥ 1.2 Mev. A detailed description of the satellite and of the electron spectrometer will appear in a study of outer zone electron intensities (Williams and Smith, to be published).

Mass and magnetic dipole shielding against electrons of the artificial radiation belt

Computations of magnetic shielding system masses required for protection against electrons of various energies have been performed. We have also obtained a comparison of the required shielding masses for a space vehicle traversing circular orbits through the anomaly in the artificial radiation belt (ARB) at altitudes of 200, 400, 600, and 800 km and inclined at 30° to the earth's equatorial plane: first with a magnetic superconducting solenoidal shielding system approximated by a point dipole and then with a two-layer composite material shielding system consisting of an outer layer of aluminum and an inner layer of lead. The aluminum thickness equaled the practical range of 10-Mev electrons, and the lead was used to attenuate the bremsstrahlung to specified skin dose rates. The averaged electron flux in ARB, used in estimating dose, was computed to be sufficiently accurate for missions not shorter than 100 hr and more accurate for longer missions. The material shielding mass, primarily designed for protection when appreciable bremsstrahlung occur, was at best (no lead) an order of magnitude larger than that of the magnetic shielding system. The mass of the cryogenic system was neglected, being a fraction of the combined mass of the solenoid and support structure.