Resolving electrons from protons in ATIC

The Advanced Thin Ionization Calorimeter (ATIC) experiment is designed for high energy cosmic ray ion detection. The possibility to identify high energy primary cosmic ray electrons in the presence of the ‘background’ of cosmic ray protons has been studied by simulating nuclear-electromagnetic cascade showers using the FLUKA Monte Carlo simulation code. The ATIC design, consisting of a graphite target and an energy detection device, a totally active calorimeter built up of 2.5 cm × 2.5 cm × 25.0 cm BGO scintillator bars, gives sufficient information to distinguish electrons from protons. While identifying about 80% of electrons as such, only about 2 in 10,000 protons (@ 150 GeV) will mimic electrons. In September of 1999 ATIC was exposed to high-energy electron and proton beams at the CERN H2 beam line, and this data confirmed the electron detection capabilities of ATIC. From 2000-12-28 to 2001-01-13 ATIC was flown as a long duration balloon test flight from McMurdo, Antarctica, recording over 360 h of data and allowing electron separation to be confirmed in the flight data. In addition, ATIC electron detection capabilities can be checked by atmospheric gamma-ray observations.     

Why does the total pressure on the subsolar magnetopause differ from the solar wind dynamic pressure?

Based on analysis of MHD equations and the results of numerical simulation in the magneto-sheath it is demonstrated that the total pressure on the magnetopause differs from the solar wind dynamic pressure in the majority of cases. From the equation of motion it follows that the total pressure is reduced due to deflection from the Sun-Earth line. At the same time, it increases because of formation of a magnetic barrier. This result is consistent with experimentally observed expansion of the magnetosphere for the radial direction of the interplanetary magnetic field, when no magnetic barrier is formed. In this paper we compare the behavior of pressure along the Sun-Earth line for the northward and radial interplanetary field, using the results of numerical MHD simulation and observational data from THEMIS. In the isotropic MHD approximation, the difference between the total pressure on the subsolar magnetopause at northern and radial IMFs does not exceed 10–12 percent. However, in the anisotropic approximation this difference increases up to 15–20 percent. The results of anisotropic modeling well agree with observed averaged profiles of pressure components in the subsolar magnetosheath.     

Phase asynchrony between coronal index and sunspot numbers

In this paper, the phase asynchrony between coronal index and sunspot numbers is investigated. It is found that, (1) the sunspot numbers begin one month earlier than coronal index, which should mathematically lead to phase asynchrony between them but with a slight effect; (2) the 11-year Schwabe cycle is the only one period with statistical significance for coronal index and sunspot numbers, and the difference between the length of the Schwabe cycle of them should also lead to phase asynchrony between them; (3) although coronal index and sunspot numbers are coherent in low-frequency components corresponding to the 11-year Schwabe cycle, they are asynchronous in phase in high-frequency components; (4) their different definitions and physical meanings may be a major reason why there is a phase asynchrony between them.     

Modelling of protons spectra encountered in space using medical accelerator and its microdosimetric characterization

Radiation environments in space are mainly composed of protons coming from the Galactic Cosmic Rays (GCRs) pervading the universe, the Solar Particle Events (SPEs) resulting from solar flares and coronal mass ejections, and the two Van Allen Belts surrounding the Earth due to the presence of the geomagnetic field trapping charged particles. Their wide spectra of energies up to hundreds of GeV imply diverse radiobiological effects to astronauts and radiation damage to electronics in the spacecraft. Even if lower in abundance, heavy ions such as He, C, O, Si, Fe are present in space and constitute an even bigger hazard due to their high penetrability and high linear energy transfer (LET). Most irradiation facilities available for research and testing worldwide provide usually only monoenergetic beams of high-energy protons or other heavier particles limiting studies of radiobiological effects and effects on electronics to a set of discrete energies.This paper introduces a procedure where a proton fluence spectra of interest for space radiation protection, previously generated by Monte Carlo simulations was delivered using a clinical proton therapy accelerator. Particularly, it reports the first results of modelling a proton radiation field in space in the energy range from 70 to 230 MeV during a single experimental session by programming a treatment planning system (TPS) to deliver required proton irradiation energies. Moreover, the angular distribution of the proton irradiation field has been varied to reproduce the isotropic exposure experienced by humans in space. The obtained proton radiation field was characterized using a 3D sensitive volume SOI microdosimeter developed by the Centre for Medical Radiation Physics (CMRP), University of Wollongong, Australia.     

Can an impulsive variation of the solar wind plasma pressure trigger a plasma bubble? A case study based on CSES,Swarm and THEMIS data

During the August 25, 2018 geomagnetic storm, the new borne CSES-01 satellite and the Swarm A satellite detected a really large equatorial plasma bubble (EPB) in the post-midnight sector over western Africa. We investigated the features of this deep ionospheric plasma depletion using data from the Langmuir probes on-board CSES-01 and Swarm A satellites, and data from the high-precision magnetometer and the electric field detector instruments on-board CSES-01. Using also plasma and magnetic field data from THEMIS-E satellite we found that, during the passage of the magnetic cloud that drove the geomagnetic storm, an impulsive variation lasting about ten minutes characterized the solar wind (SW) pressure. The analysis of the delay time, between the occurrence of such impulsive variation and the detection of the plasma bubble, suggests a possible link between the SW pressure impulsive variation as identified by THEMIS-E and the generation of the EPB as detected by CSES-01 and Swarm A. We put forward the hypothesis that the SW pressure impulsive variation might have triggered an eastward prompt penetrating electric field that propagated from high to equatorial latitudes, overlapping in the nightside region to the zonal westward electric field, causing either a reduction or an inversion, at the base of the EPB triggering.     

Characterisation of residual ionospheric errors in bending angles using GNSS RO end-to-end simulations

Global Navigation Satellite System (GNSS) radio occultation (RO) is an innovative meteorological remote sensing technique for measuring atmospheric parameters such as refractivity, temperature, water vapour and pressure for the improvement of numerical weather prediction (NWP) and global climate monitoring (GCM). GNSS RO has many unique characteristics including global coverage, long-term stability of observations, as well as high accuracy and high vertical resolution of the derived atmospheric profiles. One of the main error sources in GNSS RO observations that significantly affect the accuracy of the derived atmospheric parameters in the stratosphere is the ionospheric error. In order to mitigate the effect of this error, the linear ionospheric correction approach for dual-frequency GNSS RO observations is commonly used. However, the residual ionospheric errors (RIEs) can be still significant, especially when large ionospheric disturbances occur and prevail such as during the periods of active space weather. In this study, the RIEs were investigated under different local time, propagation direction and solar activity conditions and their effects on RO bending angles are characterised using end-to-end simulations. A three-step simulation study was designed to investigate the characteristics of the RIEs through comparing the bending angles with and without the effects of the RIEs. This research forms an important step forward in improving the accuracy of the atmospheric profiles derived from the GNSS RO technique.     

Radiation efects on MHD stagnation point flow of nano fluid towards a stretching surface with convective boundary condition

The aim of the present paper is to study the numerical solutions of the steady MHD two dimensional stagnation point flow of an incompressible nano fluid towards a stretching cylinder.The effects of radiation and convective boundary condition are also taken into account.The model used for the nanofluid incorporates the effects of Brownian motion and thermophoresis.The resulting nonlinear momentum,energy and nano particle equations are simplifed using similarity transformations.Numerical solutions have been obtained for the velocity,temperature and nanoparticle fraction profles.The influence of physical parameters on the velocity,temperature,nanoparticle fraction,rates of heat transfer and nanoparticle fraction are shown graphically.     

Space patrol: Variants of the optical barrier scheme

Different variants of the space patrol system to be designed for discovering and cataloging space objects hazardous for the Earth have been investigated. The basic idea of this system is to create an optical barrier using the telescopes deployed in a heliocentric orbit. Difficulties (as well as ways of overcoming them) of this program are analyzed, associated with form and position of the orbit of a space object relative to the patrol spacecraft, determination of orbit parameters, and mutual motion of space objects and the telescopes on spacecraft. The barrier’s schemes with scanning vertical or horizontal belts are considered. Some examples of observational conditions are presented for space objects crossing the barrier region: angular positions, velocities, distances, and numbers of days during which they are observed in the barrier region. The barrier’s characteristics are given for telescopes deployed in the orbits of the Earth and Venus.     

Physical Modeling of Electromagnetic Interference in Unmanned Aerial Vehicle under Action of the Electric Transport Contact Network

The technique was developed for studying the noise immunity of electronic systems of unmanned aerial vehicles on the basis of physical modeling. The mathematical models, the scheme of a test bench, and examples of parameter calculation for physical modeling of electromagnetic interference in communication lines under the influence of switching magnetic fields of electric transport contact network are proposed. An example of physical modeling of electromagnetic interference in communication lines is presented.     

Observations of wave activity in the ionosphere over South Africa in geomagnetically quiet and disturbed periods

The present paper deals with observations of wave activity in the period range 1–60 min at ionospheric heights over the Western Cape, South Africa from May 2010 to July 2010. The study is based on the Doppler type sounding of the ionosphere. The Doppler frequency shift measurements are supplemented with measurements of collocated Digisonde DPS-4D at SANSA Space Sciences, Hermanus. Nine geomagnetically quiet days and nine geomagnetically active days were included in the study. Waves of periods 4–30 min were observed during the daytime independent of the level of geomagnetic activity. Amplitudes of 10–30 min waves always increased between 14:00 and 16:15 UT (16:00–18:15 LT). Secondary maxima were observed between 06:00 and 07:00 UT (08:00–09:00 LT). The maximum wave amplitudes occurred close to the time of passage of the solar terminator in the studied region which is known to act as a source of gravity waves.