On the Large-Scale Structure of the Universe as given by the Voronoi Diagrams

The size distributions of 2D and 3D Voronoi cells and of cells of Vp(2,3),-2D cut of 3D Voronoi diagram-are explored, with the single-parameter (re-scaled) gamma distribution playing a central role in the analytical fitting. Observational evidence for a cellular universe is briefly reviewed. A simulated Vp(2,3) map with galaxies lying on the cell boundaries is constructed to compare, as regards general appearance, with the observed CfA map of galaxies and voids, the parameters of the simulation being so chosen as to reproduce the largest observed void size.     

Can we determine the filament chirality by the filament footpoint location or the barb-bearing?

We attempt to propose a method for automatically detecting the solar filament chirality and barb bearing. We first introduce the concept of an unweighted undirected graph and adopt the Dijkstra shortest path algorithm to recognize the filament spine. Then, we use the polarity inversion line(PIL) shift method for measuring the polarities on both sides of the filament, and employ the connected components labeling method to identify the barbs and calculate the angle between each barb and the spine to determine the bearing of the barbs, i.e., left or right. We test the automatic detection method with Hα filtergrams from the Big Bear Solar Observatory(BBSO) Hα archive and magnetograms observed with the Helioseismic and Magnetic Imager(HMI) on board the Solar Dynamics Observatory(SDO). Four filaments are automatically detected and illustrated to show the results. The barbs in different parts of a filament may have opposite bearings. The filaments in the southern hemisphere(northern hemisphere) mainly have left-bearing(rightbearing) barbs and positive(negative) magnetic helicity, respectively. The tested results demonstrate that our method is efficient and effective in detecting the bearing of filament barbs. It is demonstrated that the conventionally believed one-to-one correspondence between filament chirality and barb bearing is not valid.The correct detection of the filament axis chirality should be done by combining both imaging morphology and magnetic field observations.     

Studying the errors in the estimation of the variation of energy by the “patched-conics” model in the three-dimensional swing-by

The swing-by maneuver is a technique used to change the energy of a spacecraft by using a close approach in a celestial body. This procedure was used many times in real missions. Usually, the first approach to design this type of mission is based on the “patched-conics” model, which splits the maneuver into three “two-body dynamics.” This approach causes an error in the estimation of the energy variations, which depends on the geometry of the maneuver and the system of primaries considered. Therefore, the goal of the present paper is to study the errors caused by this approximation. The comparison of the results are made with the trajectories obtained using the more realistic restricted three-body problem, assumed here to be the “real values” for the maneuver. The results shown here describe the effects of each parameter involved in the swing-by. Some examples using bodies in the solar system are used in this part of the paper. The study is then generalized to cover different mass parameters, and its influence is analyzed to give an idea of the amount of the error expected for a given system of primaries. The results presented here may help in estimating errors in the preliminary mission analysis using the “patched-conics” approach.     

Is the solar cycle timed by a clock?

Dicke (1978) has argued that the phase of the solar cycle appears to be coupled to an internal clock: shorter cycles are usually followed by longer ones, as if the Sun remembers the correct phase. The data set is really too short to demonstrate the presence of a phase memory, but phase and amplitude of the cycle are strongly correlated for 300 yr or more. It is shown that this memory effect can be explained by mean field theory in terms of fluctuations in , which induce coherent changes in the frequency and amplitude of a dynamo wave. It is concluded that there is neither a strong observational indication nor a theoretical need for an extra timing device, in addition to the one provided by dynamo wave physics.Dedicated to Cornelis de Jager     

Monitoring the Dynamics of the Ionosphere–Plasmasphere System by Ground-Based ULF Wave Observations

Cross-spectral analysis of ULF wave measurements recorded at ground magnetometer stations closely spaced in latitude allows accurate determinations of magnetospheric field line resonance (FLR) frequencies. This is a useful tool for remote sensing temporal and spatial variations of the magnetospheric plasma mass density. The spatial configuration of the South European GeoMagnetic Array (SEGMA, 1.56 <  L <  1.89) offers the possibility to perform such studies at low latitudes allowing to monitor the dynamical coupling between the ionosphere and the inner plasmasphere. As an example of this capability we present the results of a cross-correlation analysis between FLR frequencies and solar EUV irradiance (as monitored by the 10.7-cm solar radio flux F10.7) suggesting that changes in the inner plasmasphere density follow the short-term (27-day) variations of the solar irradiance with a time delay of 1–2 days. As an additional example we present the results of a comparative analysis of FLR measurements, ionospheric vertical soundings and vertical TEC measurements during the development of a geomagnetic storm.     

The saturation of the cosmic diffuse γ-ray background by the Seyfert galaxy component

The nature of the diffuse cosmic background in the low -ray energy range has been widely discussed but not definitively solved. Unresolved active galaxies have become good candidates for its origin ever since they have been identified as -ray emitting objects. In particular, the summed contribution of Seyfert galaxies is expected to be dominant to such an extent that a straight forward calculation, based on their volume emissivity, predicts a considerable excess above the observed level of the isotropic background flux. In this letter we explore different ways to reconcile the observational data on these active galactic nuclei with the measured intensity of the cosmic diffuse -radiation.     

Exploring the characteristics of the flare from PMN J0218–2307 by Fermi-LAT

PMN J0218-2307(4 FGL J0218.9-2305) is classified as a blazar candidate with unknown type(BCU) in the fourth source catalog from the Fermi Large Area Telescope(Fermi-LAT).With the updated Fermi-LAT Pass 8 data,the γ-ray flaring activity toward PMN J0218-2307 is detected.The test statistic(TS) value of PMN J0218-2307 in energy band of 100 MeV-500 GeV is 133.893 with a significance level of 10.96σ.The maximum-likelihood photon flux is(8.131 ± 1.359) × 10~(-9) ph cm~(-2) s~(-1).A significantγ-ray flare in the period from 2008 August 4 to 2019 August 25 is found from the source.The spectral characteristics of GeV energy band of PMN J0218-2307 is similar to that of flat-spectrum radio quasars(FSRQs) in the local Universe.     

On the Fluxes of Dust Particles Detected near the Lunar Surface by the Chang’e 3 Lander

Solar System Research - We analyze the origin of dust particles in the near-surface layer of the Moon, the fluxes of which were measured in the Chang’e 3 lunar mission carried out by the...     

Superrotation of the thermosphere by global deposition of meteoroids?

Mitra has suggested that the Superrotation of the upper atmosphere is caused by a deposition of meteoroids. The meteoroids are assumed to impart to the atmosphere the excess of their orbital angular momentum per unit mass over the Earth's angular momentum per unit mass. The process is to take place in the height region above 150 km. Only above this height is a Superrotation of the atmosphere observed. In this report the forces that tend to make the atmosphere corotate with the Earth are analysed. It is shown that the most important of these forces is ion drag, and not viscous drag as postulated by Mitra. As the net angular spin momentum imparted by the meteoroids seems to be less than Mitra's estimate and its main part is applied to the atmosphere at altitudes much lower than 150 km, the hypothesis that meteoroids provide a significant contribution to the Superrotation is rejected.     

On ‘the Solar Flare Myth’ postulated by Gosling

The Solar Flare Myth postulated by Gosling (1993) is a misunderstanding. It is true that most sources of coronal mass ejections (CMEs) cannot be classified as flares in the common old sense of that word. However, just for this reason the term eruptive flare has been introduced for all solar active phenomena in which an opening of field lines is involved and which lead to magnetic-field and mass ejections resulting in a CME. The process is essentially the same in all events, irrespective of' whether only adisparition brusque without any chromospheric brightening or a major two-ribbon flare is involved in it; the only difference is the different strength of the magnetic field in which the process was accomplished. The major two-ribbon (cosmic-ray) flares clearly represent the most energetic events of this kind, and, therefore, it is very misleading to claim that solar flares in general are phenomena with very little importance for solar-terrestrial physics.     

Is dark matter an illusion created by the gravitational polarization of the quantum vacuum?

Assuming that a particle and its antiparticle have the gravitational charge of the opposite sign, the physical vacuum may be considered as a fluid of virtual gravitational dipoles. Following this hypothesis, we present the first indications that dark matter may not exist and that the phenomena for which it was invoked might be explained by the gravitational polarization of the quantum vacuum by the known baryonic matter.     

Solar Wind Acceleration by the Dissipation of Alfvén Waves

Axford and McKenzie [1992] suggested that the energy released in impulsive reconnection events generates high frequency Alfvén waves. The kinetic equation for spectral energy density of waves is derived in the random phase approximation. Solving this equation we find the wave spectrum with the power law "−1" in the low frequency range which is matched to the spectrum above the spectral brake with the power low "−1.6." The heating rate of solar wind protons due to the dissipation of Alfvén waves is obtained. This revised version was published online in July 2006 with corrections to the Cover Date.     

A Parametric Survey of the CME Triggering Process by Numerical Simulations

Observations indicate that solar coronal mass ejections (CMEs) are closely associated with reconnection-favored flux emergence, which was explained in the emerging flux trigger mechanism for CMEs by Chen & Shibata based on numerical simulations. We present a parametric survey of the triggering agent: its polarity orientation, position, and the amount of the unsigned flux. The results suggest that whether a CME can be triggered depends on both the amount and location of the emerging flux, in addition to its polarity orientation. A diagram is presented to show the eruption and non-eruption regimes in the parameter space. The work is aimed at providing useful information for the space weather forecast.     

Apparatus Weighting Functions in measuring the line-of-sight velocities by the ‘center of gravity’ method

The conception of the Apparatus Weighting Function (AWF), numerically characterizing the contributions of different layers of the solar atmosphere to indications of the apparatus used is introduced. For the detection of line-of-sight velocities, measuring the shifts of the center of gravity of a spectral line profile, AWFs have been calculated for several single lines used by the authors in their observations of the photospheric velocity field. A comparison of AWFs is given for instruments, based on the principles of measuring both the center of gravity shifts and intensity differences in the line wings.     

On the covering of a Hill’s region by solutions in the restricted three-body problem

We consider two classical celestial-mechanical systems: the planar restricted circular three-body problem and its simplification, the Hill’s problem. Numerical and analytical analyses of the covering of a Hill’s region by solutions starting with zero velocity at its boundary are presented. We show that, in all considered cases, there always exists an area inside a Hill’s region that is uncovered by the solutions.     

Photochemical fractionation of16O in the space medium modeled by resonance excitation of CO by H-Lyman α

Inferences about the formation of primordial matter in our solar system rest on analysis of the earliest preserved materials in meteorites, of the structure of the solar system today, and of matter in evolving stellar systems elsewhere.The isotope distribution in meteorites suggests that molecular excitation processes similar to those observed today in circumstellar regions and dark interstellar clouds were operating in the early solar nebula. Laboratory model experiments together with these observations give evidence on the thermal state of the source medium from which refractory meteoritic dust formed. They indicate that resonance excitation of the broad isotopic bands of molecules such as¹²C¹⁶O, MgO, O₂, AlO, and OH by strong UV line sources such as H-L, MgII, H, and CaII may induce selective reactions resulting in the anomalous isotopic composition of oxygen and possibly other elements in refractory oxide condensates in meteorites.