near-Earth Radiation Environment Research Articles

Overview, progress and next steps for our understanding of the near-earth space radiation and plasma environment: Science and applications

The Near-Earth Space Radiation and Plasma Environment falls within the realm of G3 Cluster (G3 refers to ‘Near-Earth Radiation and Plasma Environment’ of the ‘Coupled Geospace System’) under the COSPAR (Committee On Space Research)/International Space Weather Action Teams (ISWAT) Initiative. The diverse and dynamic particle populations from this region pose challenges from both science and space weather-impact perspectives. The G3 cluster has intimate connections with solar, heliosphere clusters, and the other Geospace ones (G1, G2) through a chain of physical processes. This paper reviews recent scientific advances in understanding this complex space environment, identifies gaps in research and space weather applications, and maps out our recommendations on priorities for the next 5–10 years.

Tree-rings reveal two strong solar proton events in 7176 and 5259 BCE

The Sun sporadically produces eruptive events leading to intense fluxes of solar energetic particles (SEPs) that dramatically disrupt the near-Earth radiation environment. Such events have been directly studied for the last decades but little is known about the occurrence and magnitude of rare, extreme SEP events. Presently, a few events that produced measurable signals in cosmogenic radionuclides such as 14C, 10Be and 36Cl have been found. Analyzing annual 14C concentrations in tree-rings from Switzerland, Germany, Ireland, Russia, and the USA we discovered two spikes in atmospheric 14C occurring in 7176 and 5259 BCE. The ~2% increases of atmospheric 14C recorded for both events exceed all previously known 14C peaks but after correction for the geomagnetic field, they are comparable to the largest event of this type discovered so far at 775 CE. These strong events serve as accurate time markers for the synchronization with floating tree-ring and ice core records and provide critical information on the previous occurrence of extreme solar events which may threaten modern infrastructure.

East–West Proton Flux Anisotropy Observed with the PAMELA Mission

Abstract We present a study of the east–west anisotropy of trapped-proton fluxes in low-Earth orbit based on the measurements of the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) experiment. The differential intensities of eastward- and westward-traveling protons detected in the South Atlantic Anomaly region were estimated as a function of equatorial pitch angle and drift shell, for six energy bins between 80 MeV and 2 GeV. We found that, as a consequence of the strong atmospheric gradient coupled with the large gyroradius in this energy range, the intensities of eastward fluxes exceed those of westward fluxes by a factor of ∼10–20. However, the reported directional asymmetry also depends on the sign of the local flux gradient, resulting in more intense westward fluxes beyond the radial distances where the inner belt peaks. PAMELA observations can be used to improve the description of the near-Earth radiation environment at lowest altitudes and highest trapping energies, where current theoretical and empirical models are affected by the largest uncertainties.

Extensive study of radiation dose on human body at aviation altitude through Monte Carlo simulation

The diverse near-Earth radiation environment due to cosmic rays and solar radiation has direct impact on human civilization. In the present and upcoming era of increasing air transfer, it is important to have precise idea of radiation dose effects on human body during air travel. Here, we calculate the radiation dose on the human body at the aviation altitude, also considering the shielding effect of the aircraft structure, using Monte Carlo simulation technique based on Geant4 toolkit. We consider proper 3D mathematical model of the atmosphere and geomagnetic field, updated profile of the incoming particle flux due to cosmic rays and appropriate physics processes. We use quasi-realistic computational phantoms to replicate the human body (male/female) for the effective dose calculation and develop a simplified mathematical model of the aircraft (taking Boeing 777-200LR as reference) for the shielding study. We simulate the radiation environment at the flying altitude (at 10 km and considering geomagnetic latitude in the range of 45–50°), as well as at various locations inside the fuselage of the aircraft. Then, we calculate the dose rates in the different organs for both male and female phantoms, based on latest recommendations of International Commission on Radio logical Protection. This calculation shows that the sex-averaged effective dose rate in human phantom is 5.46 μSv/h, whereas, if we calculate weighted sum of equivalent dose contributions separately in female and male body: total weighted sum of equivalent dose rate received by the female phantom is 5.72 μSv/h and that by the male phantom is 5.20 μSv/h. From the simulation, we also calculate the numerous cosmogenic radionuclides produced inside the phantoms through activation or spallation processes which may induce long-term biological effects.

Monitor and Prediction of Near-Earth Radiation Environment in the Frame of Space Monitoring Data Center at Moscow State University

AbstractRadiation environment of near-Earth space is one of the most important factors of space weather. Space Monitoring Data Center of Moscow State University provides operational monitor and forecast of radiation conditions both at Geostationary Orbits (GEO) and at Low Earths Orbits (LEO) of the near-Earth space using data of recent space missions (Vernov, CORONAS series) and current (Lomonosov, Meteor-M, Electro-L) ones. Internet portal of Space Monitoring Data Center of Skobeltsyn Institute of Nuclear Physics of Lomonosov Moscow State University (SINP MSU - [swx.sinp.msu.ru]) provides possibilities to monitor and analyze the space radiation conditions in the real time mode together with the geomagnetic and solar activity including hard X-ray and gamma-emission of solar flares.

The influence of solar flares on the near-Earth space radiation environment in March and April 2013: Possibilities of operational monitoring

This paper deals with the operational analysis of the influence of solar flares, which produced solar cosmic rays, on the near-Earth radiation environment in space during the period from March 1 to April 18, 2013.

On the parametrization of the energetic-particle pitch-angle diffusion coefficient

Context: Solar energetic particle (SEP) events are one of the key ingredients of the near-Earth radiation environment. Pitch-angle scattering by fluctuations imposed on the large-scale magnetic field is assumed to be the basic physical process behind diffusive propagation of SEPs in the heliosphere. Various pitch-angle diffusion models have been suggested to parametrize the wave-particle interactions, based on the original results of the classical quasi-linear theory of particle scattering and improved new approaches.

Geomagnetic storms could alter near‐Earth radiation environment

Potentially hazardous space weather could affect satellites traversing the inner radiation zone, closer to Earth than previously thought, a new study shows. The Earth's radiation belts have a two‐layer structure, and it had been thought that most geomagnetic storms, which are triggered by solar activity, affected only the outer belt. However, simulations by Shprits et al. show that during a very large geomagnetic storm, electrons could actually be accelerated in the inner radiation belt layer. Changes in the near‐Earth radiation environment could then persist for several years after a large geomagnetic storm. High‐energy electrons can damage satellites, and the altered radiation environment near Earth could significantly reduce the lifetime of satellites in that zone. The authors suggest that a large geomagnetic storm that reached the inner radiation belt could have potentially devastating economic impacts. (Space Weather, doi:10.1029/2011SW000662, 2011)

Radiation belt storm probes: Resolving fundamental physics with practical consequences

The fundamental processes that energize, transport, and cause the loss of charged particles operate throughout the universe at locations as diverse as magnetized planets, the solar wind, our Sun, and other stars. The same processes operate within our immediate environment, the Earth's radiation belts. The Radiation Belt Storm Probes (RBSP) mission will provide coordinated two-spacecraft observations to obtain understanding of these fundamental processes controlling the dynamic variability of the near-Earth radiation environment. In this paper we discuss some of the profound mysteries of the radiation belt physics that will be addressed by RBSP and briefly describe the mission and its goals.

Introduction to special section on the Earth‐Moon‐Mars Radiation Environment Module

[1] The United States is preparing to return humans to the Moon and is setting the stage for exploration to Mars and beyond. However, it is unclear if long missions outside of low-Earth orbit (LEO) can be accomplished with acceptable risk. The central objective of the NASA Living With a Star Earth-Moon-Mars Radiation Environment Module (EMMREM) is to develop and validate a numerical module for completely characterizing time-dependent radiation exposure in the Earth-Moon-Mars and interplanetary space environments. EMMREM currently provides the capability to predict radiation exposure in the interplanetary environment outside of Earth’s protective atmosphere and magnetosphere and at various heights of a nominal Mars atmosphere. Ongoing and future efforts will fold in the effects of Earth’s atmosphere and the geomagnetic field so that the radiation environment can be predicted near the Earth’s surface, at LEO, and at various geomagnetic latitudes. EMMREM is being designed for broad use by researchers to predict radiation exposure by integrating over time-evolving incident particle distributions from interplanetary space. The EMMREM represents a growing and developing system of coupled models that describe particle acceleration and transport in interplanetary space and secondary transport through shielding materials, atmospheres, and various parts of the human body to determine doses, dose rates, and linear energy transfer spectra. Thus, EMMREM makes the explicit connection from observations and simulations of solar energetic particles and galactic cosmic rays to characterization of the potential hazards of the radiation environment and to acute radiation risks. The papers in this special section will describe the following. [2] 1. Observations near 1 AU from ACE, GOES, and IMP 5 for the historic August 1972 event to characterize the near-Earth radiation environment are used as timedependent boundary conditions near 1 AU in an energetic particle propagation and acceleration module (the Energetic Particle Radiation Environment Module (EPREM)) to predict the radiation environment throughout the inner heliosphere. Observations at Ulysses (near 5 AU) are then used to validate the EPREM predictions. [3] 2. Event-based simulations in the inner heliosphere predict time-dependent estimates of organ exposures for human crews in deep space. [4] 3. A paper provides a risk assessment approaches for solar particle events. [5] 4. Several papers describe a model for prompt solar energetic particle (SEP) dose rate forecasting for the Earth-Moon system. [6] 5. The transmission of SEPs and galactic cosmic rays (GCRs) through the Mars atmosphere predicts the radiation environment at Mars. [7] 6. The coupling between the Energetic Particle Radiation Environment Module and magnetohydrodynamic models improves the predictions of the radiation environment in the inner heliosphere. [8] 7. Ulysses observations and a model of GCRs are used to improve our understanding of recent GCR fluxes and associated GCR dose rates throughout the inner heliosphere. [9] 8. A paper provides predictions of the linear energy transfer spectrum for the Cosmic Ray Telescope for the Effects of Radiation detector during the Lunar Reconnaissance Orbiter mission. [10] 9. Several papers describe predictions of the space radiation environment during gradual solar energetic particle events using physics-based particle acceleration models. [11] Thus, the papers in this special section of Space Weather introduce the EMMREM project and provide a baseline for current understanding of the space environment beyond Earth’s protective atmosphere and magnetosphere.

Bubble detector characterization for space radiation

In light of the importance of the neutron contribution to the dose equivalent received by space workers in the near-Earth radiation environment, there is an increasing need for a personal dosimeter that is passive in nature and able to respond to this neutron field in real time. Recent Canadian technology has led to the development of a bubble detector, which is sensitive to neutrons, but insensitive to low linear energy transfer (LET) radiation. By changing the composition of the bubble detector fluid (or “superheat”), the detectors can be fabricated to respond to different types of radiation. This paper describes a preliminary ground-based research effort to better characterize the bubble detectors of different compositions at various charged-particle accelerator facilities, which are capable of simulating the space radiation field.

Radiation environment measurements with the cosmic ray experiments on-board the KITSAT-1 and PoSAT-1 micro-satellites

The success of the Cosmic Radiation Environment and Dosimetry (CREDO) experiment carried on-board the UoSAT-3 micro-satellite (launched in 1990) has lead to the development of a new instrument called the Cosmic-Ray Experiment (CRE) which has flown on-board the KITSAT-1 and PoSAT-1 micro-satellites, launched in 1992 and 1993 respectively. The results from both CRE instruments show excellent agreement with those of CREDO for the galactic cosmic-ray environment. However, there are some differences in the CRE and CREDO response to the trapped proton environment of the South Atlantic Anomaly which can be explained by the differences in the detector response time. The fit between the flight results and predictions from the standard models is generally good, but some differences are noted. The CRE and CREDO instruments should provide continuous coverage of the near-Earth radiation environment across a complete solar cycle. This is important in view of the dynamic nature of the radiation environment-as amply demonstrated by the results from the CRRES spacecraft. >

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>