Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userThe detection of ultra-relativistic electrons in low Earth orbit
92
0
0.0
(
0
)
Added by
Athanassios Katsiyannis
Publication date
2017
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
Aims. To better understand the radiation environment in low Earth orbit (LEO), the analysis of in-situ observations of a variety of particles, at different atmospheric heights, and in a wide range of energies, is needed. Methods. We present an analysis of energetic particles, indirectly detected by the Large Yield RAdiometer (LYRA) instrument on board ESAs Project for On-board Autonomy 2 (PROBA2) satellite as background signal. Combining Energetic Particle Telescope (EPT) observations with LYRA data for an overlapping period of time, we identified these particles as electrons with an energy range of 2 to 8 MeV. Results. The observed events are strongly correlated to geo-magnetic activity and appear even during modest disturbances. They are also well confined geographically within the L=4-6 McIlwain zone, which makes it possible to identify their source. Conclusions. Although highly energetic particles are commonly perturbing data acquisition of space instruments, we show in this work that ultra-relativistic electrons with energies in the range of 2-8 MeV are detected only at high latitudes, while not present in the South Atlantic Anomaly region.
rate research
Read More
Very low Earth orbits (VLEO), typically classified as orbits below approximately 450 km in altitude, have the potential to provide significant benefits to spacecraft over those that operate in higher altitude orbits. This paper provides a comprehensive review and analysis of these benefits to spacecraft operations in VLEO, with parametric investigation of those which apply specifically to Earth observation missions. The most significant benefit for optical imaging systems is that a reduction in orbital altitude improves spatial resolution for a similar payload specification. Alternatively mass and volume savings can be made whilst maintaining a given performance. Similarly, for radar and lidar systems, the signal-to-noise ratio can be improved. Additional benefits include improved geospatial position accuracy, improvements in communications link-budgets, and greater launch vehicle insertion capability. The collision risk with orbital debris and radiation environment can be shown to be improved in lower altitude orbits, whilst compliance with IADC guidelines for spacecraft post-mission lifetime and deorbit is also assisted. Finally, VLEO offers opportunities to exploit novel atmosphere-breathing electric propulsion systems and aerodynamic attitude and orbit control methods. However, key challenges associated with our understanding of the lower thermosphere, aerodynamic drag, the requirement to provide a meaningful orbital lifetime whilst minimising spacecraft mass and complexity, and atomic oxygen erosion still require further research. Given the scope for significant commercial, societal, and environmental impact which can be realised with higher performing Earth observation platforms, renewed research efforts to address the challenges associated with VLEO operations are required.
Energetic electrons inside Earths outer Van Allen belt pose a major radiation threat to space-borne electronics that often play vital roles in our modern society. Ultra-relativistic electrons with energies greater than or equal to two Megaelectron-volt (MeV) are of particular interest due to their high penetrating ability, and thus forecasting these >=2 MeV electron levels has significant meaning to all space sectors. Here we update the latest development of the predictive model for MeV electrons inside the Earths outer radiation belt. The new version, called PreMevE-2E, focuses on forecasting ultra-relativistic electron flux distributions across the outer radiation belt, with no need of in-situ measurements except for at the geosynchronous (GEO) orbit. Model inputs include precipitating electrons observed in low-Earth-orbits by NOAA satellites, upstream solar wind conditions (speeds and densities) from solar wind monitors, as well as ultra-relativistic electrons measured by one Los Alamos GEO satellite. We evaluated a total of 32 supervised machine learning models that fall into four different classes of linear and neural network architectures, and also successfully tested ensemble forecasting by using groups of top-performing models. All models are individually trained, validated, and tested by in-situ electron data from NASAs Van Allen Probes mission. It is shown that the final ensemble model generally outperforms individual models overs L-shells, and this PreMevE-2E model provides reliable and high-fidelity 25-hr (~1-day) and 50-hr (~2-day) forecasts with high mean performance efficiency values. Our results also suggest this new model is dominated by non-linear components at low L-shells (< ~4) for ultra-relativistic electrons, which is different from the dominance of linear components at all L-shells for 1 MeV electrons as previously discovered.
The PAMELA experiment is devoted to the study of cosmic rays in Low Earth Orbit with an apparatus optimized to perform a precise determination of the galactic antimatter component of c.r. It is constituted by a number of detectors built around a permanent magnet spectrometer. PAMELA was launched in space on June 15th 2006 on board the Russian Resurs-DK1 satellite for a mission duration of three years. The characteristics of the detectors, the long lifetime and the orbit of the satellite, will allow to address several aspects of cosmic-ray physics. In this work we discuss the observational capabilities of PAMELA to detect the electron component above 50 MeV. The magnetic spectrometer allows a detailed measurement of the energy spectrum of electrons of galactic and Jovian origin. Long term measurements and correlations with Earth-Jupiter 13 months synodic period will allow to separate these two contributions and to measure the primary electron Jovian component, dominant in the 50-70 MeV energy range. With this technique it will also be possible to study the contribution to the electron spectrum of Jovian e- reaccelerated up to 2 GeV at the Solar Wind Termination Shock.
Space radiation is well-known to pose serious issues to solid-state high-energy sensors. Therefore, radiation models play a key role in the preventive assessment of the radiation damage, duty cycles, performance and lifetimes of detectors. In the context of HERMES-SP mission we present our investigation of AE8/AP8 and AE9/AP9 specifications of near-Earth trapped radiation environment. We consider different circular Low-Earth orbits. Trapped particles fluxes are obtained, from which maps of the radiation regions are computed, estimating duty cycles at different flux thresholds. Outcomes are also compared with published results on in-situ measurements.
Foreshock disturbances -- large-scale (~1000 km to >30,000 km), transient (~5-10 per day - lasting ~10s of seconds to several minutes) structures [1,2] - generated by suprathermal (>100 eV to 100s of keV) ions [3,4] arise upstream of Earths bow shock formed by the solar wind colliding with the Earths magnetosphere. They have recently been found to accelerate ions to energies of several keV [5,6]. Although electrons in Saturns high Mach number (M > 40) bow shock can be accelerated to relativistic energies (nearly 1000 keV) [7], it has hitherto been thought impossible to accelerate electrons at the much weaker (M < 20) Earths bow shock beyond a few 10s of keV [8]. Here we report observations of electrons energized by foreshock disturbances to energies up to at least ~300 keV. Although such energetic electrons have been previously reported, their presence has been attributed to escaping magnetospheric particles [9,10] or solar events [11]. These relativistic electrons are not associated with any solar activity nor are they of magnetospheric origin. Further, current theories of ion acceleration in foreshock disturbances cannot account for electrons accelerated to the observed relativistic energies [12-17]. These electrons are clearly coming from the disturbances, leaving us with no explanation as to their origin.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
