Cosmic Observations Research Articles

Analysis of GNSS radio occultation data from satellite ZH-01

The electromagnetic satellite Zhangheng 01 (ZH-01) was successfully launched on February 2, 2018. The GNSS Radio Occultation (GRO) receiver on board the satellite is able to observe the occultation events of GPS and BeiDou navigation satellites. We analyzed the data acquired during the in-orbit testing period. We concludes that the GRO ionosphere inversion results are reasonable, the trend is correct, the satellite can observe about 600 ionosphere occultation events each day. The global coverage of more than 30000 consecutive GRO events in more than two months were analyzed and compared with COSMIC observations: both the GRO and COSMIC occultation can realize global coverage: the NmF2 and HmF2 global distributions are similar and change obviously with latitude. We used three digisondes at different latitudes to analyze and compare the spatio-temporally consistent GRO data: the RMSE of GRO NmF2 relative to digisonde is better than 9.41%, the correlation coefficient is better than 0.8682: the relative RMSE of HmF2 is better than 7.80% and the correlation coefficient is better than 0.7066.

Forecast and analysis of the cosmological redshift drift

The cosmological redshift drift could lead to the next step in high-precision cosmic geometric observations, becoming a direct and irrefutable test for cosmic acceleration. In order to test the viability and possible properties of this effect, also called Sandage–Loeb (SL) test, we generate a model-independent mock data set in order to compare its constraining power with that of the future mock data sets of Type Ia Supernovae (SNe) and Baryon Acoustic Oscillations (BAO). The performance of those data sets is analyzed by testing several cosmological models with the Markov chain Monte Carlo (MCMC) method, both independently as well as combining all data sets. Final results show that, in general, SL data sets allow for remarkable constraints on the matter density parameter today varOmega _m on every tested model, showing also a great complementarity with SNe and BAO data regarding dark energy parameters.

The Hellenic Open University Cosmic Ray Telescope: Research and Educational Activities

The Hellenic Open University Cosmic Ray Telescope consists of three autonomous stations installed at the University Campus in the city of Patras. Each station comprises three large (≈ 1 m2) plastic scintillators and one or more Codalema type RF antennas detecting Extensive Air Showers (EAS), originating from primary particles with energy greater than 10 TeV. The operation and the performance of the Telescope is presented briefly, emphasising the educational activities foreseen in the framework of the HEllenic LYceum Cosmic Observatories Network (HELYCON).

Detecting the neutrinos mass hierarchy from cosmological data

We propose a new parameterization to measure the neutrino mass hierarchy, namely $\Delta=(m_3-m_1)/(m_1+m_3)$ which is dimensionless and varies in the range $[-1,1]$. Taking into account the results of neutrino oscillation experiments, $\Delta$ is the unique parameter for determining all the masses of neutrinos, and a positive (negative) sign of $\Delta$ denotes the normal (inverted) mass hierarchy. Adopting the currently available cosmic observations, we find that the normal mass hierarchy is slightly favored, and the mass of lightest neutrino is less than $0.030$ eV for the normal mass hierarchy and $0.024$ eV for the inverted mass hierarchy at $95\%$ confidence level.

Primary mass discrimination of high energy cosmic rays using PNN and k-NN methods

Probabilistic neural network (PNN) and k-Nearest Neighbors (k-NN) methods are widely used data classification techniques. In this paper, these two methods have been used to classify the Extensive Air Shower (EAS) data sets which were simulated using the CORSIKA code for three primary cosmic rays. The primaries are proton, oxygen and iron nuclei at energies of 100 TeV–10 PeV. This study is performed in the following of the investigations into the primary cosmic ray mass sensitive observables. We propose a new approach for measuring the mass sensitive observables of EAS in order to improve the primary mass separation. In this work, the EAS observables measurement has performed locally instead of total measurements. Also the relationships between the included number of observables in the classification methods and the prediction accuracy have been investigated. We have shown that the local measurements and inclusion of more mass sensitive observables in the classification processes can improve the classifying quality and also we have shown that muons and electrons energy density can be considered as primary mass sensitive observables in primary mass classification. Also it must be noted that this study is performed for Tehran observation level without considering the details of any certain EAS detection array.

Wide-field LOFAR-LBA power-spectra analyses: Impact of calibration, polarization leakage and ionosphere

AbstractContamination due to foregrounds, calibration errors and ionospheric effects pose major challenges in detection of the cosmic 21 cm signal in various Epoch of Reionization (EoR) experiments. We present the results of a study of a field centered on 3C196 using LOFAR Low Band observations, where we quantify various wide field and calibration effects such as gain errors, polarized foregrounds, and ionospheric effects. We observe a ‘pitchfork’ structure in the power spectrum of the polarized intensity in delay-baseline space, which leaks into the modes beyond the instrumental horizon. We show that this structure arises due to strong instrumental polarization leakage (~30%) towards Cas A which is far away from primary field of view. We measure a small ionospheric diffractive scale towards CasA resembling pure Kolmogorov turbulence. Our work provides insights in understanding the nature of aforementioned effects and mitigating them in future Cosmic Dawn observations.

GRAINE project, prospects for scientific balloon-borne experiments

We are pushing forward with the GRAINE project, a 10-MeV to 100-GeV cosmic γ-ray observation project that uses an emulsion telescope with high angular resolution (0.08° at 1–2GeV) and polarization sensitivity, and a large aperture area (∼10m2), by repeating long-duration balloon flights. Through various ground experiments, a balloon-borne experiment in 2011, and a balloon-borne experiment in 2015, the feasibility of cosmic γ-ray observations with a balloon-borne emulsion telescope was pioneered. Through scientific balloon-borne experiments, we can attempt to achieve the following: pioneering polarization observations for high-energy γ rays from pulsars, active galactic nuclei, flares, and γ-ray bursts; direct probing of proton acceleration by π0 feature detection and approaching an emission mechanism with a spatial structure for supernova remnants; resolving GeV γ-ray excess at the galactic center region; probing new physics beyond the Planck scale by polarization observations with high-energy γ rays propagating over cosmological distances; observing transient sources, e.g. γ-ray bursts and flares, with a high sensitivity, high photon statistics and polarization sensitivity. Developments in scientific balloon-borne experiments are ongoing.

RadioAstron space-VLBI project: studies of masers in star forming regions of our Galaxy and megamasers in external galaxies

AbstractObservations of the masers in the course of RadioAstron mission yielded detections of fringes for a number of sources in both water and hydroxyl maser transitions. Several sources display numerous ultra-compact details. This proves that implementation of the space VLBI technique for maser studies is possible technically and is not always prevented by the interstellar scattering, maser beaming and other effects related to formation, transfer, and detection of the cosmic maser emission. For the first time, cosmic water maser emission was detected with projected baselines exceeding Earth Diameter. It was detected in a number of star-forming regions in the Galaxy and two megamaser galaxies NGC 4258 and NGC 3079. RadioAstron observations provided the absolute record of the angular resolution in astronomy. Fringes from the NGC 4258 megamaser were detected on baseline exceeding 25 Earth Diameters. This means that the angular resolution sufficient to measure the parallax of the water maser source in the nearby galaxy LMC was directly achieved in the cosmic maser observations. Very compact features with angular sizes about 20\muas\, have been detected in star-forming regions of our Galaxy. Corresponding linear sizes are about 5-10 million kilometers. So, the major step from milli- to micro-arcsecond resolution in maser studies is achieved by the RadioAstron mission. The existence of the features with extremely small angular sizes is established. Further implementations of the space–VLBI maser instrument for studies of the nature of cosmic objects, studies of the interaction of extremely high radiation field with molecular material and studies of the matter on the line of sight are planned.

EOF analysis of COSMIC observations on the global zonal mean temperature structure of the Upper Troposphere and Lower Stratosphere from 2007 to 2013

This work presents the results of a Conventional Empirical Orthogonal Function Analysis on daily global zonal mean temperature profiles in the Upper Troposphere and Lower Stratosphere (15–35 km), as measured by the FORMOSAT-3/COSMIC mission from January 2007 to June 2013. For validation, results were compared with ERA-Interim reanalysis. Results show that, the leading global EOF mode (27%) from COSMIC is consistent with temperature anomalies due to the tropical cooling associated with boreal winter Sudden Stratospheric Warmings (SSW). The second global EOF mode from COSMIC (15.3%) is consistent with temperature anomalies due to the Quasi-biennial Oscillation (QBO). The third global mode from COSMIC (10.9%) is consistent with temperature anomalies due to the El Nino Southern Oscillation. This work also shows that the second northern hemisphere EOF mode from COSMIC (16.8%) is consistent with temperature anomalies due Rossby-wave breaking (RWB) which is expected to only be resolved by a high vertical and temporal resolution dataset like COSMIC. Our work concludes that the use of a high vertical and temporal resolution dataset like COSMIC yields non-seasonal EOF modes that are consistent with relatively more intricate temperature anomalies due to the SSW, QBO, ENSO and RWB.

Temperature properties in the tropical tropopause layer and their correlations with Outgoing Longwave Radiation: FORMOSAT-3/COSMIC observations

The properties of temperature at the level of lapse rate minimum (LRM) in the tropical tropopause layer between 20°S and 20°N are investigated using 3-year radio occultation observations based on the FORMOSAT-3/COSMIC mission from November of 2006 to October of 2009. The correlations between this LRM temperature and Outgoing Longwave Radiation (OLR) are analyzed by 5° × 5° grids in longitude and latitude. Two primary regions, one from 60°E to 180°E and the other from 90°W to 30°E, are found to have higher correlations and can be associated with regions of lower OLR values. The patterns of this spatial distributions of regions with higher correlations begin to change more obviously when the altitude ascends to the level of Cold Point Tropopause (CPT). This correlation at the LRM altitude in annual and seasonal scales also shows spatial distributions associated with OLR intensities. The altitudinal dependence of the correlations between temperature and OLR is further analyzed based on grids of high correlations with significance at LRM altitude, for the two primary regions. The results show that for the different time scales in this analysis (3-year, annual, and seasonal), the correlations all gradually decrease above the LRM levels but maintain a significant level to as high as 2.5–3.5 km. Below the LRM level, the correlation decreases with a slower rate as the altitude descends and still keeps significant at the deep 5 km level. These suggest that the vertical temperature profiles could be affected by the convection mechanism for a wide range of altitudes in the troposphere even above LRM altitude. Applying the same analysis on one complete La Niña event during the survey period also reveals similar features.

Geometry and growth contributions to cosmic shear observables

We explore the sensitivity of weak-lensing observables to the expansion history of the Universe and to the growth of cosmic structures, as well as the relative contribution of both effects to constraining cosmological parameters. We utilize ray-tracing dark-matter-only $N$-body simulations and validate our technique by comparing our results for the convergence power spectrum with analytic results from past studies. We then extend our analysis to non-Gaussian observables which cannot be easily treated analytically. We study the convergence (equilateral) bispectrum and two topological observables, lensing peaks and Minkowski functionals, focusing on their sensitivity to the matter density ${\mathrm{\ensuremath{\Omega}}}_{m}$ and the dark energy equation of state $w$. We find that a cancellation between the geometry and growth effects is a common feature for all observables and exists at the map level. It weakens the overall sensitivity by factors of up to 3 and 1.5 for $w$ and ${\mathrm{\ensuremath{\Omega}}}_{m}$, respectively, with the bispectrum worst affected. However, combining geometry and growth information alleviates the degeneracy between ${\mathrm{\ensuremath{\Omega}}}_{m}$ and $w$ from either effect alone. As a result, the magnitudes of marginalized errors remain similar to those obtained from growth-only effects, but with the correlation between the two parameters switching sign. These results shed light on the origin of the cosmology sensitivity of non-Gaussian statistics and should be useful in optimizing combinations of observables.

Inflation from periodic extra dimensions

We discuss a realization of a small field inflation based on string inspired supergravities. In theories accompanying extra dimensions, compactification of them with small radii is required for realistic situations. Since the extra dimension can have a periodicity, there will appear (quasi-)periodic functions under transformations of moduli of the extra dimensions in low energy scales. Such a periodic property can lead to a UV completion of so-called multi-natural inflation model where inflaton potential consists of a sum of multiple sinusoidal functions with a decay constant smaller than the Planck scale. As an illustration, we construct a SUSY breaking model, and then show that such an inflaton potential can be generated by a sum of world sheet instantons in intersecting brane models on extra dimensions containing orbifold. We show also predictions of cosmic observables by numerical analyzes.

Weak lensing from self-ordering scalar fields

Cosmological defects result from cosmological phase transitions in the early Universe and the dynamics reflects their symmetry-breaking mechanisms. These cosmological defects may be probed through weak lensing effects because they interact with ordinary matters only through the gravitational force. In this paper, we investigate global textures by using weak lensing curl and B modes. Non-topological textures are modeled by the non-linear sigma model (NLSM), and induce not only the scalar perturbation but also vector and tensor perturbations in the primordial plasma due to the nonlinearity in the anisotropic stress of scalar fields. We show angular power spectra of curl and B modes from both vector and tensor modes based on the NLSM. Furthermore, we give the analytic estimations for curl and B mode power spectra. The amplitude of weak lensing signals depends on a combined parameter $\epsilon^{2}_{v} = N^{-1}\left( v/m_{\rm pl} \right)^{4}$ where $N$ and $v$ are the number of the scalar fields and the vacuum expectation value, respectively. We discuss the detectability of the curl and B modes with several observation specifications. In the case of the CMB lensing observation without including the instrumental noise, we can reach $\epsilon_{v} \approx 2.7\times 10^{-6}$. This constraint is about 10 times stronger than the current one determined from the Planck. For the cosmic shear observation, we find that the signal-to-noise ratio depends on the mean redshift and the observing number of galaxies as $\propto z^{0.7}_{\rm m}$ and $\propto N^{0.2}_{\rm g}$, respectively. In the study of textures using cosmic shear observations, the mean redshift would be one of the key design parameters.

Equinoctial asymmetry in ionosphere over Indian region during 2006–2013 using COSMIC measurements

In this study, the ionospheric equinoctial asymmetry (EA, defined as different ionospheric behaviour in the two equinoxes) is investigated in the maximum electron density (NmF2) and the corresponding altitude (hmF2) over the Indian region (∼5–30° N geog. lat., 60–100° E geog. long.) during quiet geomagnetic conditions (Ap≤20) and varying phase of solar activity (2006–2013, F10.7 ∼65–192 sfu) using COSMIC observations. Both NmF2 and hmF2 exhibited strong solar-activity dependence and which increased with the increase in solar activity throughout the day. We found EA in NmF2 is not just a daytime phenomenon but also occurs in morning and nighttime during high solar-activity. The EA in NmF2 over equatorial-low latitude is found solar-dependant in nighttime and morning (weaker/stronger in low-/high-solar activity) whereas stronger/weaker in noontime in low-/high-solar activity years (higher NmF2 in vernal in 2007–2009, 2013) respectively. Whereas for hmF2, EA is stronger in nighttime and weaker in morning for all years over both equatorial and low-latitudinal regions and weaker/moderate in low-/high-solar activity for noontime respectively. We found F10.7P and Dst index in the equinoxes playing a dominant role throughout the day and the chemical compositions (O, N2 and neutral mass densities) also a responsible factor for the EA in NmF2 and hmF2 in the morning and nighttime respectively.

Abnormal geophysical and seismotectonic processes observed during the period of preparation and development of the earthquake with a magnetude of 8,8 Maule 2010 (Chile)

Focal zone, basic shock, jerking of strongest aftershocks and progress of seismic energy release during the aftershock process of the earthquake Maule 27.02.2010 (M W =8,8) in Chile have been analyzed. Macroseismic manifestations, tectonic position of the focus and reconstruction of acting plane position in the focus have been considered. Geophysical treatment of anomalous gravimagnetic disturbances and seismic precursors induced in variations of magnetic field and geoacoustic fields of the Earth during preparation of the basic shock and of three strongest iterative shocks on March 11 —16 2010 has been done for the first time. It has been shown that application of present-day cosmic observations, which allow to analyze gravity disturbances (so far only coseismic), reflected on the Earth’s surface makes possible to consider the precursors of seismic shocks of the arthquake Maule and other seismic events in a new way. Long-, middle- and short-term approaches to prognostication of strong seismic events both on land and sea have been stated

Seasonal characteristics of COSMIC measurements over Indian sub-continent during different phases of solar activity

The seasonal characteristics of F2 region is investigated using peak electron density (NmF2) and corresponding altitude (hmF2) measurements obtained by COSMIC observations over Indian sub-continent (Geog. 5–40°N and 60–100°E) for the complete mission during the solar cycle 24 (Apr, 2006–Dec, 2013). A stronger EIA is observed in summer and winter during high solar activity whereas occurs in equinoxes during all levels of solar activity. The noontime winter anomaly in NmF2 is absent/weaker during low (2006–2009)/high (2010–2013) solar activity over equator whereas is stronger in low and moderate solar activity (2006–2007 and 2010–2011) but absent in minimum and maximum (2008–2009 and 2012–2013) solar activity over low-latitude respectively. The higher hmF2 is observed over the equator throughout the day (equator: 230–415km and low-latitude: 220–340km). The observed parameters, NmF2 and hmF2 are compared with the IRI-modeled values using CCIR and URSI options. The comparison exhibits a higher discrepancy in NmF2 in nighttime and morning for equatorial and lower discrepancy for the whole day over the low-latitude whereas smaller (<20%) discrepancy exists in the hmF2 throughout the day using both IRI options. In conclusion, we found CCIR option in more agreement to the observed values for both equatorial and low-latitude regions respectively.

Cosmological implications of the dark matter equation of state

In this paper, we study a model which is composed of the cosmological constant and dark matter with nonzero equation of state parameter, which could be called as [Formula: see text]wDM. In the synchronous gauge, we obtain the perturbation equations of dark matter, and deduce the evolution equations of growth factor about the dark matter and baryons. Based on the Markov Chain Monte Carlo (MCMC) method, we constrain this model by the recently available cosmic observations which include cosmic microwave background (CMB) radiation, baryon acoustic oscillation (BAO), type Ia supernovae (SNIa) and [Formula: see text] data points from redshift-space distortion (RSD). The results present a tighter constraint on the model than the case without [Formula: see text] data. In 3[Formula: see text] regions, we find the dark matter equation of state parameter [Formula: see text]. The currently available cosmic observations do not favor the nonzero dark matter equation of state parameter, no deviation from the lambda cold dark matter ([Formula: see text]CDM) model is found in 1[Formula: see text] region.

Diurnal variability of the global tropical tropopause: results inferred from COSMIC observations

Short and long-term variability of the tropical tropopause controls the exchange of minor constituents between the troposphere and the stratosphere. We present the diurnal variability of the global tropical tropopause altitude and temperature using 7 years of COSMIC observations. The aim of the study is to extract diurnal tropopause signals and their impact on stratosphere-troposphere exchange processes. The possible role of atmospheric tides and convection in controlling the tropopause characteristics are discussed. The most significant and new observation is that in the deep tropics the cold-point tropopause altitude is higher and temperatue is cooler over the land (ocean) during evening to late evening hours (afternoon to early evening). Lower tropopause altitude allows the stratospheric air intrusion into the troposphere during the day time. The combined effect of diurnal tropopause altitude changes and turbulent mixing increases the possibility of stratospheric intrusions. A warmer forenoon tropopause allows increased injection of water vapor from the troposphere to the lower stratosphere. Over the tropical land (ocean), the zonal mean diurnal amplitude is 130–200 m (140–180 m) for tropopause altitude and 0.6–0.9 K (0.6–0.8 K) for tropopause temperature.

A Combined Heterotic String and K&#228;hler Manifold Elucidation of Ordinary Energy, Dark Matter, Olbers’s Paradox and Pure Dark Energy Density of the Cosmos

We utilize the topological-geometrical structure imposed by the Heterotic superstring theory on spacetime in conjunction with the K3 Kahler manifold to explain the mysterious nature of dark matter and its coupling to the pure dark energy density of the cosmos. The analogous situations in the case of a Kerr black hole as well as the redundant components of the Riemannian tensor are pointed out and the final result was found to be in complete agreement with all previous theoretical ones as well as all recent accurate measurements and cosmic observations. We conclude by commenting briefly on the Cantorian model of Zitterbewegung and the connection between Olbers’s paradox and dark energy.

МЕТОДИКА РОЗРАХУНКУ НАВЕДЕНИХ ВИТРАТ ПРИ ПРОЕКТУВАННІ КОМБІНОВАНОЇ НИЗЬКООРБІТАЛЬНОЇ СУПУТНИКОВОЇ СИСТЕМИ

The article provides a method for calculating the costs when designing a promising embodiment of a low-bit satellite system. For Ukraine, the prospects for this option lies in the fact that their own means of achieving a large number of satellites in orbit are applied. At the same time, satellites are multifunctional and used to organize communication and broadcasting, the sounding of the atmosphere and the surface of the Earth, subsurface locations, cosmic observation, data collection from the Internet sensors. The space group consists of mini, macro-, nanosterans, which are delivered to the orbit of a domestic rocket carrier into orbit. The technical and economic efficiency of the satellite system lies not only in the above advantages, but also in its hierarchical construction - combination of the root satellite, ministerial repeater, macrovers. The article provides an analysis of other low-bit satellite systems. A feature of the study of the combined LEO is the fact that the proposed construction of the satellite system allows the use of technological distributed registries as one of the through digital technologies. In digital transformation of the economy, the technology of distributed registers plays the same role as Internet things, cloud computing, 5G and Big Data technologies. The method of calculating the presented costs is to calculate the cost of the development, production and operation of the system at the stage of its design. The costs of developing space and ground segments are included in the total capital costs. The costs of developing a space segment are highlighted on the cost of developing a root satellite, a minivan-repeater, microscope. The same approach is also laid for the cost of exploitation of the space segment. When calculating the costs of the ground segment as the main component of earth stations, antenna systems, radio transmission microwaves and radio receiving microwaves, information processing devices, terminal equipment are taken as the main components of earth stations. The approximate cost of serial production of root sieuine, mini satellite, retrograder, microsatellite is indicated. The estimated cost of one minute of access in the studied combined LEO and in the existing "close" to the appointment of a low-bit satellite system is given.