Status of the GAMMA-400 project

The preliminary design of the new space gamma-ray telescope GAMMA-400 for the energy range 100 MeV–3 TeV is presented. The angular resolution of the instrument, 1–2° at E_γ ∼ 100 MeV and ∼0.01° at E_γ > 100 GeV, its energy resolution ∼1% at E_γ > 100 GeV, and the proton rejection factor ∼10⁶ are optimized to address a broad range of science topics, such as search for signatures of dark matter, studies of Galactic and extragalactic gamma-ray sources, Galactic and extragalactic diffuse emission, gamma-ray bursts, as well as high-precision measurements of spectra of cosmic-ray electrons, positrons, and nuclei.     

GRB observed by IBIS/PICsIT in the MeV energy range

We present the preliminary results of a systematic search for GRB and other transients in the publicly available data for the IBIS/PICsIT (0.2–10 MeV) detector on board INTEGRAL. Lightcurves in 2–8 energy bands with time resolution from 1 to 62.5 ms have been collected and an analysis of spectral and temporal characteristics has been performed. This is the nucleus of a forthcoming first catalog of GRB observed by PICsIT.     

Sunspot numbers,interplanetary magnetic field,and cosmic ray intensity at earth: Nexus for the twentieth century

The pivotal role played by the interplanetary magnetic field (B) in modulating galactic cosmic ray (GCR) intensity in the heliosphere is described. We show that the inverse correlation observed by Forbush (1958) between GCRs and sunspot numbers (SSNs) is reflected in high correlation between SSNs and B (cc = 0.94). The SSN data are available since 1700 and the derived B data since 1835. The paleo-cosmic ray data are available for several millennia in the form of ¹⁰Be radionuclide sequestered in polar ice. The data of the ion chambers (ICs) at the Cheltenham–Fredericksburg–Yakutsk (CFY) sites are combined to create a data string for 1937–1988. In turn, these data are used to extend the measurements of the low energy GCR ions (>0.1 GeV) at balloon altitudes at high latitudes in Russia to 1937. These data are then correlated to B and the fit parameters are used to extend the low energy ion data to 1900, creating the instrumental era GCR time series for the twentieth century. The derived GCR time series is compared to ¹⁰Be measured at two sites in Greenland, namely Dye 3 and NGRIP for 1900–2000 to check the internal consistency of datasets for the long-term trend. We find that the annual mean rate (%) for 1965 at NGRIP is an outlier. We replace it with the mean of 1964 and 1965 rates and construct a new re-normalized time series at NGIP, improving the agreement with the derived instrumental era GCR time series for the twentieth century as well. This should encourage its use by heliophysics community for varied applications.     

Dependence of the 27-day variation of cosmic rays on the global magnetic field of the Sun

We show that the higher range of the heliolongitudinal asymmetry of the solar wind speed in the positive polarity period (A > 0) than in the negative polarity period (A < 0) is one of the important reasons of the larger amplitudes of the 27-day variation of the galactic cosmic ray (GCR) intensity in the period of 1995–1997 (A > 0) than in 1985–1987 (A < 0). Subsequently, different ranges of the heliolongitudinal asymmetry of the solar wind speed jointly with equally important corresponding drift effect are general causes of the polarity dependence of the amplitudes of the 27-day variation of the GCR intensity. At the same time, we show that the polarity dependence is feeble for the last unusual minimum epoch of solar activity 2007–2009 (A < 0); the amplitude of the 27-day variation of the GCR intensity shows only a tendency of the polarity dependence. We present a three dimensional (3-D) model of the 27-day variation of GCR based on the Parker’s transport equation. In the 3-D model is implemented a longitudinal variation of the solar wind speed reproducing in situ measurements and corresponding divergence-free interplanetary magnetic field (IMF) derived from the Maxwell’s equations. We show that results of the proposed 3-D modeling of the 27-day variation of GCR intensity for different polarities of the solar magnetic cycle are in good agreement with the neutron monitors experimental data. To reach a compatibility of the theoretical modeling with observations for the last minimum epoch of solar activity 2007–2009 (A < 0) a parallel diffusion coefficient was increased by ∼40%.     

Detection of the high energy component of Jovian electrons in Low Earth Orbit with the PAMELA experiment

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 3 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.     

The ground-based large-area wide-angle γ-ray and cosmic-ray experiment HiSCORE

The question of the origin of cosmic rays and other questions of astroparticle and particle physics can be addressed with indirect air-shower observations above 10 TeV primary energy. We propose to explore the cosmic ray and γ-ray sky (accelerator sky) in the energy range from 10 TeV to 1 EeV with the new ground-based large-area wide angle (ΔΩ ∼ 0.85 sterad) air-shower detector HiSCORE (Hundred^∗i Square-km Cosmic ORigin Explorer). The HiSCORE detector is based on non-imaging air-shower Cherenkov light-front sampling using an array of light-collecting stations. A full detector simulation and basic reconstruction algorithms have been used to assess the performance of HiSCORE. First prototype studies for different hardware components of the detector array have been carried out. The resulting sensitivity of HiSCORE to γ-rays will be comparable to CTA at 50 TeV and will extend the sensitive energy range for γ-rays up to the PeV regime. HiSCORE will also be sensitive to charged cosmic rays between 100 TeV and 1 EeV.     

Modulation of galactic cosmic rays in a north–south asymmetrical heliosphere

Observations made with the two Voyager spacecraft confirmed that the solar wind decelerates to form the heliospheric termination shock. Voyager 1 crossed this termination shock at ∼94 AU in 2004, while Voyager 2 crossed it in 2007 at a different heliolatitude, about 10 AU closer to the Sun. These different positions of the termination shock confirm the dynamic and cyclic nature of the shock’s position. Observations from the two Voyager spacecraft inside the heliosheath indicate significant differences between them, suggesting that apart from the dynamic nature caused by changing solar activity there also may exist a global asymmetry in the north–south (polar) dimensions of the heliosphere, in addition to the expected nose–tail asymmetry. This relates to the direction in which the heliosphere is moving in interstellar space and its orientation with respect to the interstellar magnetic field. In this paper we focus on illustrating the effects of this north–south asymmetry on modulation of galactic cosmic ray Carbon, between polar angles of 55° and 125°, using a numerical model which includes all four major modulation processes, the termination shock and the heliosheath. This asymmetry is incorporated in the model by assuming a significant dependence on heliolatitude of the thickness of the heliosheath. When comparing the computed spectra between the two polar angles, we find that at energies E < ∼1.0 GeV the effects of the assumed asymmetry on the modulated spectra are insignificant up to 60 AU from the Sun but become increasingly more significant with larger radial distances to reach a maximum inside the heliosheath. In contrast, with E > ∼1.0 GeV, these effects remain insignificant throughout the heliosphere even very close to the heliopause. Furthermore, we find that a higher local interstellar spectrum for Carbon enhances the effects of asymmetric modulation between the two polar angles at lower energies (E < ∼300 MeV). In conclusion, it is found that north–south asymmetrical effects on the modulation of cosmic ray Carbon depend strongly on the extent of the geometrical asymmetry of the heliosheath together with the assumed value of the local interstellar spectrum.     

Cosmic Ray Energetics And Mass for the International Space Station (ISS-CREAM)

The Cosmic Ray Energetics And Mass (CREAM) instrument is configured with a suite of particle detectors to measure TeV cosmic-ray elemental spectra from protons to iron nuclei over a wide energy range. The goal is to extend direct measurements of cosmic-ray composition to the highest energies practical, and thereby have enough overlap with ground based indirect measurements to answer questions on cosmic-ray origin, acceleration and propagation. The balloon-borne CREAM was flown successfully for about 161 days in six flights over Antarctica to measure elemental spectra of Z = 1–26 nuclei over the energy range 10¹⁰ to >10¹⁴ eV. Transforming the balloon instrument into ISS-CREAM involves identification and replacement of components that would be at risk in the International Space Station (ISS) environment, in addition to assessing safety and mission assurance concerns. The transformation process includes rigorous testing of components to reduce risks and increase survivability on the launch vehicle and operations on the ISS without negatively impacting the heritage of the successful CREAM design. The project status, including results from the ongoing analysis of existing data and, particularly, plans to increase the exposure factor by another order of magnitude utilizing the International Space Station are presented.     

The LAGEOS satellites orbit and Yukawa-like interactions

LAGEOS II general relativity pericenter precession has been analysed in terms of the errors produced by the mismodelling of both the gravitational and non-gravitational perturbations acting on the satellite orbit. The accuracy in the pericenter determination may be considered as an upper-bound value for the estimate of the strength α of a possible new-long-range-interaction described by a Yukawa-like potential. In the present work we have focused on the constraints in α that can be obtained with the current best multi-satellites gravity field model EGM96 (α < 2.6 × 10⁻¹⁰) and also with the first promising models from the CHAMP (α < 1.8 × 10⁻¹⁰) and GRACE (α < 1.2 × 10⁻¹⁰) gravimetric missions. These results represent, potentially, an improvement of two or three orders-of-magnitude with respect to the best constraints obtained in the past with Earth–LAGEOS and Lunar–LAGEOS data (|α| < 10⁻⁵–10⁻⁸). The impact of the non-gravitational perturbations mismodelling in the final error budget has been determined together with the improvements obtainable in the constraint of the strength α with the proposed LARES satellite.     

The role of radial perpendicular diffusion and latitude dependent acceleration along the solar wind termination shock

A numerical model, based on Parker’s transport equation, describing the modulation of anomalous cosmic rays and containing diffusive shock acceleration is applied. The role of radial perpendicular diffusion at the solar wind termination shock, and as the dominant diffusion coefficient in the outer heliosphere, is studied, in particular the role it plays in the effectiveness of the acceleration of anomalous protons and helium when its latitude dependence is changed. It is found that the latitudinal enhancement of radial perpendicular diffusion towards the heliospheric poles and along the termination shock has a prominent effect on the acceleration of these particles. It results in a ‘break’ in the energy spectrum for anomalous protons at ∼6.0 MeV, causing the spectral index to change from E^−1.38 to E^−2.23, but for anomalous helium at ∼3.0 MeV, changing the spectral index from E^−1.38 to E^−2.30. When approaching the simulated TS, the changes in the modulated spectra as they unfold to a ‘steady’ power law shape at energies below 50 MeV are much less prominent as a function of radial distances when radial perpendicular diffusion is increased with heliolatitude.     

Possible consequences of a disk around B0656+14 on e–e and near-1 Hz gravitational wave production

Nearby pulsars B0656+14 and Geminga were proposed in the literature as the main sources of cosmic-ray positrons observed near Earth above 10 GeV. B0656+14 has comparable distance from Earth, similar magnetic field and period of Geminga. However, observations in the R and I bands indicate the presence of a disk of approximately 10⁻⁴ M_⊙ around B0656+14. Radio and pulsed γ-ray flux observations from this pulsar are also consistent with supernova fallback material and disk entering the light cylinder and partially quenching the development of electromagnetic showers in the magnetosphere. If this is the case, B0656+14 has unlikely given any contribution to e⁺ and e⁻ observed near Earth. Absolute flux measurements and the level of anisotropy in the high energy electron and positron arrival directions above 50 GeV will help in revealing if none, one of both nearby pulsars are sources of these particles observed near Earth.     

Simulation of depth–dose distributions for various ions in polyethylene medium

Study of depth–dose distributions for intermediate energy ion beams in tissue-like media such as polyethylene (CH₂)_n provides a good platform for further improvements in the fields of hadrontherapy and space radiation shielding. The depth–dose distributions for ¹²C ions at various energies and for light and intermediate ion beams (³He, ¹⁶O, ²⁰Ne and ²⁸Si) as well as for heavy ions ⁵⁶Fe in polyethylene were estimated by using simulation toolkit: Geant4. Calculations were performed mainly by considering two different combinations of standard electromagnetic (EM), binary cascade (BIC), statistical multifragmentation (SMF) and Fermi breakup (FB) models. The energies of the ion beams were selected to achieve the Bragg peaks at predefined position (∼60 mm) and as per their availability. Variations of peak-to-entrance ratio (from 7.44 ± 0.05 to 8.87 ± 0.05), entrance dose (from 2.89 ± 0.01 to 203.71 ± 0.63 MeV/mm) and entrance stopping power (from 3.608 to 208.858 MeV/mm, calculated by SRIM) with atomic number (Z) were presented in a systematic manner. The better peak-to-entrance ratio and less entrance dose in the region Z = 2 to 8 (i.e. ³He to ¹⁶O) may provide the suitability of the ion beams for hadrontherapy.     

Statistical study of the detection of solar protons of highest energies at 20 January 2005

On January 20, 2005, 7:02–7:04 UT the Aragats Multichannel Muon Monitor (AMMM) registered enhancement of the high energy secondary muon flux (energy threshold ∼5 GeV). The enhancement, lasting 3 min, has statistical significance of ∼4σ and is related to the X7.1 flare seen by the GOES satellite and the ground level enhancement detected by the world-wide network of neutron monitors and by muon detectors. The most probable proton energy corresponding to the measured 5 GeV muon flux is within 23–30 GeV. Due to upmost importance of the detection of solar particles of highest energies in presented paper we perform detailed statistical analysis of the detected peak. The statistical technique introduced in the paper is also appropriate for the searches of sources of ultra-high energy cosmic rays.     

X-ray redshifts with the International X-ray Observatory (IXO)

We explore the capabilities of the future space science mission IXO (International X-ray Observatory) for obtaining cosmological redshifts of distant Active Galactic Nuclei (AGNs) using the X-ray data only. We first find in which regions of the X-ray luminosity (L_X) versus redshift (z) plane the weak but ubiquitous Fe Kα narrow emission line can deliver an accurate redshift (δz < 5%) as a function of exposure time, using a CCD-based Wide Field Imager (IXO/WFI) as the one baselined for IXO. Down to a 2–10 keV X-ray flux of 10⁻¹⁴ erg cm⁻² s⁻¹ IXO/WFI exposures of 100 ks, 300 ks and 1 Ms will deliver 20%, 40% and 60% of the redshifts. This means that in a typical 18′ × 18′ IXO/WFI field of view, 4, 10 and 25 redshifts will be obtained for free from the X-ray data alone, spanning a wide range up to z ∼ 2–3 and fairly sampling the real distribution. Measuring redshifts of fainter sources will indeed need spectroscopy at other wavebands.     

The heliospheric modulation of cosmic rays: Effects of a latitude dependent solar wind termination shock

Observations made with the two Voyager spacecraft confirmed that the solar wind decelerates to form the heliospheric termination shock and that it has begun its merger with the local interstellar medium. The compression ratio of this shock affects galactic cosmic rays when they enter the heliosphere. Hydrodynamic (HD) models show that the compression ratio can have a significant latitude dependence; with the largest value in the nose direction of the heliosphere, becoming significantly less towards the polar regions. The modulation effects of such large latitude dependence are studied, using a well-established numerical drift and shock modulation model. We focus on computing the modulated spectra for galactic protons with emphasis on the radial and polar gradients in the equatorial plane and at a polar angle of θ = 55°, corresponding to the heliolatitude of Voyager 1. Two sets of solutions are computed and compared each time; with and without a latitude dependence for the compression ratio. All computations are done for the two magnetic field polarity cycles assuming solar minimum conditions. Including the termination shock in the model allows the study of the re-acceleration of galactic protons in the outer heliosphere. We find that for the A < 0 polarity cycle the intensity between ∼200 MeV and ∼1 GeV in the vicinity of the shock in the heliospheric equatorial plane may exceed the local interstellar value specified at the heliopause. Unfortunately, at θ = 55°, the effect is reduced. This seems not possible during an A > 0 cycle because significant modulation is then predicted between the heliopause and the termination shock, depending on how strong global gradient and curvature drifts are in the heliosheath. The overall effect of the shock on galactic protons in the equatorial plane is to reduce the total modulation as a function of radial distance with respect to the interstellar spectrum. Making the compression ratio latitude dependent enhances these effects at energies E < 200 MeV in the equatorial plane. At larger heliolatitudes these effects are even more significant. The differences in the modulation between the two drift cycles are compelling when the compression ratio is made latitude dependent but at Earth this effect is insignificant. A general result is that the computed radial gradient changes for galactic protons at and close to the TS and that these changes are polarity dependent. In line with previous work, large polarity dependent effects are predicted for the inner heliosphere and also close to the shock’s position in the equatorial plane. In contrast, at θ = 55°, the largest polarity effect occurs in the middle heliosphere (50 AU), enhanced by the latitude dependence of the compression ratio. At this latitude, the amount of proton modulation between the heliopause and the termination shock is much reduced. If galactic cosmic rays were to experience some diffusive shock acceleration over the 100–1000 MeV range at the shock, the radial gradient should change its sign in the vicinity of the shock, how large, depends on the compression ratio and the amount of drifts taking place in the outer heliosphere. The effective polar gradient shows a strong polarity dependence at Earth but this dissipates at θ = 55°, especially with increasing radial distance. This tendency is enhanced by making the compression ratio latitude dependent.     

Efficacy of oxygen-supplying capacity of Azolla in a controlled life support system

Azolla shows high growth and propagation rates, strong photosynthetic O₂-releasing ability and high nutritional value. It is suitable as a salad vegetable and can be cultured on a multi-layered wet bed. Hence, it possesses potential as a fresh vegetable, and to release O₂ and absorb CO₂ in a Controlled Ecological Life Support System in space. In this study, we investigated the O₂-providing characteristics of Azolla in a closed chamber under manned, controlled conditions to lay a foundation for use of Azolla as a biological component in ground simulation experiments for space applications. A closed test chamber, representing a Controlled Ecological Life Support System including an Azolla wet-culture device, was built to measure the changes in atmospheric O₂ and CO₂ concentrations inside the chamber in the presence of coexisting Azolla, fish and men. The amount of O₂ consumed by fish was 0.0805–0.0831 L kg⁻¹ h⁻¹ and the level of CO₂ emission was 0.0705–0.0736 L kg⁻¹ h⁻¹; O₂ consumption by the two trial volunteers was 19.71 L h⁻¹ and the volume of respiration-released CO₂ was 18.90 L h⁻¹. Under 7000–8000 Lx artificial light and Azolla wet-culture conditions, human and fish respiration and Azolla photosynthesis were complementary, thus the atmospheric O₂ and CO₂ concentrations inside chamber were maintained in equilibrium. The increase in atmospheric CO₂ concentration in the closed chamber enhanced the net photosynthesis efficiency of the Azolla colony. This study showed that Azolla has strong photosynthetic O₂-releasing ability, which equilibrates the O₂ and CO₂ concentrations inside the chamber in favor of human survival and verifies the potential of Azolla for space applications.     

X-ray study of accretion flow in narrow-line Seyfert 1 galaxies

We present the results of a systematic study of narrow-line Seyfert 1 galaxies (NLS1s) observed with XMM-Newton. The 2–12 keV X-ray spectra of NLS1s are well represented by a single power law with a photon index Γ ∼ 2. When this hard power law continuum is extrapolated into the low energy band, we found that all objects in our sample show prominent soft excess emission. This excess emission is well parameterized by the thermal emission expected from an optically thick accretion disk, and we found the following three peculiar features: (1) The derived disk temperatures are significantly higher than the expectation from a standard Shakura-Sunyaev accretion disk, if we assume a central mass of a black hole to be 10^6–8M_⊙. (2) The temperatures are distributed within narrow range (ΔkT ∼ 0.08 keV) with an average temperature of 0.18 keV in spite of the range of four orders of magnitude in luminosity (10^41–45 erg s⁻¹). (3) We found a peculiar temperature–luminosity relation, where the luminosity seems to be almost saturated in spite of the significant change in temperature, during the observations of the most luminous NLS1 PKS 0558-504. These results strongly suggest that the standard accretion disk picture is no longer appropriate in the nuclei of NLS1s. We discuss a possible origin for the soft excess component, and suggest that a slim disk may be able to explain the observational results, if the photon trapping effect is properly taken into account.     

Cowpeas and pinto beans: Performance and yields of candidate space crops in the laboratory biosphere closed ecological system

An experiment utilizing cowpeas (Vigna unguiculata L.), pinto beans (Phaseolus vulgaris L.) and Apogee ultra-dwarf wheat (Triticum sativa L.) was conducted in the soil-based closed ecological facility, Laboratory Biosphere, from February to May 2005. The lighting regime was 13 h light/11 h dark at a light intensity of 960 μmol m⁻² s⁻¹, 45 mol m⁻² day⁻¹ supplied by high-pressure sodium lamps. The pinto beans and cowpeas were grown at two different planting densities. Pinto bean production was 341.5 g dry seed m⁻² (5.42 g m⁻² day⁻¹) and 579.5 dry seed m⁻² (9.20 g m⁻² day⁻¹) at planted densities of 32.5 plants m⁻² and 37.5 plants m⁻², respectively. Cowpea yielded 187.9 g dry seed m⁻² (2.21 g m⁻² day⁻¹) and 348.8 dry seed m⁻² (4.10 g m⁻² day⁻¹) at planted densities of 20.8 plants m⁻² and 27.7 plants m⁻², respectively. The crop was grown at elevated atmospheric carbon dioxide levels, with levels ranging from 300–3000 ppm daily during the majority of the crop cycle. During early stages (first 10 days) of the crop, CO₂ was allowed to rise to 7860 ppm while soil respiration dominated, and then was brought down by plant photosynthesis. CO₂ was injected 27 times during days 29–71 to replenish CO₂ used by the crop during photosynthesis. Temperature regime was 24–28 °C day/deg 20–24 °C night. Pinto bean matured and was harvested 20 days earlier than is typical for this variety, while the cowpea, which had trouble establishing, took 25 days more for harvest than typical for this variety. Productivity and atmospheric dynamic results of these studies contribute toward the design of an envisioned ground-based test bed prototype Mars base.     

AVS-F observations of γ-ray emission during January 20, 2005 solar flare up to 140 MeV

The solar flare of January 20, 2005 (X7.1, 06:36–07:26 UT, maximum at 07:01 UT by the GOES soft X-ray data) was the most powerful one in January 2005 series. The AVS-F apparatus onboard CORONAS-F registered γ-emission during soft X-ray rising phase of this flare in two energy ranges of 0.1–20 MeV and 2–140 MeV. The highest γ-ray energy registered during this flare was ∼140 MeV. Six spectral features were registered in energy spectrum of this solar flare: annihilation + αα (0.4–0.6 MeV), ²⁴Mg + ²⁰Ne + ²⁸Si + neutron capture (1.7–2.3 MeV), ²¹Ne + ²²Ne + ¹⁶O + ¹²С (3.2–5.0 MeV), ¹⁶O (5.3–6.9 MeV), one from neutral pions decay (25–110 MeV) and one in energy band 15–21 MeV. Four of them contain typical for solar flares lines – annihilation, nuclear de-excitation and neutron capture at ¹H. Spectral feature caused by neutral pions decay was registered during several flares too. Some spectral peculiarities in the region of 15–21 MeV were first observed in solar flare energy spectrum.