Relativistic fireworks

We have studied a model of relativistic fireworks. In this model it is assumed that a series of explosions occur. In each explosion the fragments fly apart in arbitrary directions with a given velocity which is a parameter in the model.We have succeeded in obtaining an exact expression for the distribution of fragments in velocity space aftern explosions.We present an exact solution also in the limiting case of small velocity steps where the process turns into a diffusion in velocity space.The development in configuration space has been obtained through Monte-Carlo numerical simulations.The model has been applied to metagalactic cosmology. Although single explosions cannot reach the highest redshifts observed in the Hubble expansion the fireworks model offers a possibility to reach thesez-values in a few explosions.The model gives a density inhomogeneity of 20% over a tenth of the Hubble distance as seen from a typical position. Observations show a considerably greater irregular variation.The model gives a local velocity dispersion which is too great to comply with observations. A development of the model is suggested.     

Evolution of binary systems with repeated mass ejections

The effects of a series of isotropic ejections of small amounts of mass from either component of a binary system are studied. The evolution is completely different than in the case where all the mass is lost at once. When the ejections are randomly distributed in time, the final eccentricity may become larger or smaller than the initial one; the differences, however, are in most cases small. When the frequency of the explosions is higher near periastron, the final eccentricity is in most cases larger than the original value. In almost no case the system is disrupted.     

Unique first-forbidden β-decay rates for neutron-rich nickel isotopes in stellar environment

In astrophysical environments, allowed Gamow-Teller (GT) transitions are important, particularly for β-decay rates in presupernova evolution of massive stars, since they contribute to the fine-tuning of the lepton-to-baryon content of the stellar matter prior to and during the collapse of a heavy star. In environments where GT transitions are unfavored, first-forbidden transitions become important especially in medium heavy and heavy nuclei. Particularly in case of neutron-rich nuclei, first-forbidden transitions are favored primarily due to the phase-space amplification for these transitions. In this work the total β-decay half-lives and the unique first-forbidden (U1F) β-decay rates for a number of neutron-rich nickel isotopes, ^72–78Ni, are calculated using the proton-neutron quasi-particle random phase approximation (pn-QRPA) theory in stellar environment for the first time. For the calculation of the β-decay half-lives both allowed and unique first-forbidden transitions were considered. Comparison of the total half-lives is made with measurements and other theoretical calculations where it was found that the pn-QRPA results are in better agreement with experiments and at the same time are suggestive of inclusion of rank 0 and rank 1 operators in first-forbidden rates for still better results.     

The Seismic Efficiency of Space Body Impacts

The numerical analysis of the propagation of shock waves initiated by either a space body striking the Earth’s surface, or underground explosions, allows us to compare the energies required to attain the same amplitudes of shock waves at impacts and explosions. Proceeding from this and based on the data of seismic efficiency of underground explosions, the authors have estimated the fraction of the kinetic energy of a space body transformed into the energy of seismic disturbances when the body strikes the Earth. This fraction is about 10^–3, which is an order of magnitude more than the most common estimates. Space bodies decelerating and collapsing in the atmosphere also generate seismic waves in the ground due to the impact of the air-shock wave on the Earth’s surface. In this case, the seismic efficiency is considerably lower, according to the calculations, it is about 10^–5.     

Hydrogen and Helium under high pressure: A case for a classical theory of dense matter

When subject to high pressure, H₂ and ³He are expected to undergo phase transitions, and to become metallic at a sufficiently high pressure. Using a semiclassical theory of dense matter proposed by Savi and Kaanin, calculations of phase transition and metallisation pressure have been performed for these two materials. In hydrogen, metallisation occurs at p _M= (3.0 ± 0.2) Mbar, while for helium the corresponding value is p _M= (106 ± 1) Mbar. A phase transition occurs in helium at p _tr= (10.0 ± 0.4) Mbar. These values are close to the results obtainable by more rigorous methods. Possibilities of experimental verification of the calculations are briefly discussed.     

Entropy change and phase transitions in an expanding Universe

The work compiles a correlated study of a gravitational quasi equilibrium thermodynamic approach for establishing and signifying a unique behavior of the cosmological entropy and phase transitions in an expanding Universe. On the basis of prescribed boundary conditions for the cluster temperature a relation for the intra‐cluster medium (ICM) of galaxy clusters has been derived. A more productive and signifying approach of the correlation functions used for galaxy clustering phenomena shows a unique behavior of the entropy change where a phenomenon known as the gravitational phase transition occurs. This unique behavior occurs with a symmetry breaking from mild clustering to low clustering and from mild clustering to high clustering which differs from a normal symmetry breaking in material sciences. We also derive results for the specific latent heat associated with the phase transitions of 3.20 T_c and 0.55 T_c for the mildly clustered phase to the low clustered phase and from the mildly clustered phase to the highly clustered phase, respectively. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Nucleation,growth and transformation of amorphous and crystalline solids condensing from the gas phase

The condensation of solids was investigated from the initial nucleation stage through continuous film growth, using evaporation and high-energy ion-beam sputtering. At all stages the kinetics of the nucleation process and the structural characteristics of the condensed phase (glassy, polycrystalline and monocrystalline) were defined. Although many condensates were explored, the specific system discussed is germanium condensing on a variety of amorphous and crystalline substrates.The kinetic behavior observed in crystalline deposits was found consistent with the accepted atomistic model for nucleation. This allowed determination of such nucleation parameters as: the activation energies of surface diffusion,Q _d and adsorption,Q _ad ,the critical nucleus size,n ^*, and others. Values of such parameters were found to be systematic functions of the kinetic energy and flux of incident particles and of the type and temperature of the substrate.Two flux and temperature dependent structural order transitions were observed in the very initial nucleation stages and found to coincide with corresponding transitions inn ^*. Correlation was also established between these transitions and two structural transitions occurring during continuous film growth. This was aided by the occurrence of all four transitions in intermediate condensation stages, i.e. prior to coalescence of nucleation clusters into continuous film.All results were very distinctly affected by the vapor state of the adsorbates, implying considerable correlation between condensation on solid surfaces and in a vapor.Invited contribution to the Proceedings of a Workshop onThermodynamics and Kinetics of Dust Formation in the Space Medium, held at the Lunar and Planetary Institute, Houston, 6–8 September, 1978.     

Somef-values for transitions in ZrII,ZrIII and SrI

Transition probabilities were calculated for certain transitions in ZrII, ZrIII and SrI. For these allowed transitions Hartree-Fock wavefunctions were calculated for use in determining the absolute line strength. The methods developed by C. Froese-Fischer and Mayers and O'Brien for calculating the wavefunctions were used in determining those for the transitions in ZrII, ZrIII and SrI. Theoretical and experimentalf-values were compared in the case of SrI, and the results were in reasonable agreement for transition probabilities based on dipole velocity calculations.     

Chromospheric and coronal explosions in solar flares

The phenomenon described as a coronal explosion results directly from a chromospheric explosion. These two phenomena always occur together. They are the manifestations of the impulsive phase explosions in solar flares. These explosive processes occur during and immediately after the onset of the impulsive phase of flares. A previously presented model, describing the relation between the two kinds of explosions, appears to be able to explain qualitatively, and in many cases also quantitatively, the observations relevant to these explosive processes.     

Jupiter's Synchrotron Emission Induced by the Collision of Comet Shoemaker-Levy 9

From July 13 to August 21, 1994, we observed Jupiter at 1420 MHz using one of the 30-m single dishes of the Instituto Argentino de Radioastronomía. After the impact of fragment G, we detected a rapid increase of the 21cm-continuum flux, which reached the maximum (≈ 20% of Jupiter's flux) at the end of the impact period. The nature of this radiation is clearly synchrotron. We interpret it in terms of a new population of relativistic electrons (≈ 2 × 10²⁹) injected into the Jovian magnetosphere as a consequence of the impact explosions. The proposed mechanism is that the relativistic plasma was blown as magnetic clouds that flowed along the magnetic lines of force towards the jovimagnetic equator. We constructed a model in which the energies of the fresh electrons, generated within the magnetized clouds with a power law energy spectrum, were highly degraded by the comet dust grains attached to the magnetized plasma. The model can account for the spectral shape based on observations at several frequencies (de Pater et al., 1995, Science 268, 1879; Venturi et al., 1996, Astron. Astrophys. 316, 243). The energy released by the explosions under the form of relativistic electrons is of ≈ 2 × 10²⁵ erg, which represents a fraction of about 1–3 per cent of the explosion energy. The efficiency in converting the explosion energy into the relativistic electron energy is, therefore, of the same order of magnitude as that of supernova explosions. An alternative model is considered. This gives figures for the total energy and number of relativistic electrons that are similar to the corresponding ones of the favoured model. Finally, we suggest that the behavior of the flux decay in the various observed frequencies is the result of the diffusion of electrons into the loss-cone due to the resonant scattering of the electrons by Alfven waves. This revised version was published online in July 2006 with corrections to the Cover Date.     

A galactic model with a pulsating active nucleus. I

A model of galaxy with an active nucleus is investigated; The cloud in the galactic disc accretes on the core. The core temperature and hence the core luminosity becomes high because of the kinetic energy release by the accreting gas cloud. Then the gas and dust in the core is ejected outward by the radiation pressure from resonance line scattering, forms a sort of halo around the core and subsequently falls on the galactic plane. The gas and dust subsisted from star formation accretes again on the nucleus to provoke another explosion. So these processes are cyclic throughout the life of the galaxy.According to this model, the period of explosion depends only on the temperatureT of the system in such a manner as(y)=2.7×10⁶ T ^1/2. This relation can well explain the observed time scales for galactic explosions. On the other hand, the time dependence of heavy elements abundance, of the redshift of distant galaxy and of galactic luminosity is investigated. The redshift dependence of galactic distribution is also examined. It has become clear that this model can lead the inconsistent results with observational facts. The other problems concerning with galaxies or metagalaxies should be treated along this line.     

Relation of pulsars to the remnants of supernova bursts

Based on a large volume of statistical data it is shown that the spatial distributions of radio pulsars in the galaxy with characteristic ages T ≤ 10 ⁶ years and T > 10⁶ years differ significantly. The overwhelming majority of the pulsars with T ≤ 10 ⁶ years lie within a narrow band of width 400 pc around the galactic plane. A large portion of the pulsars with T > 10⁶ years is concentrated outside this zone. In the case of younger pulsars, a larger fraction of them lies within the confines of the above mentioned zone. It is also shown that pulsars with T ≤ 10 ⁶ years and the remnants of supernova explosions have essentially the same spatial distribution. These facts support the existence of a relationship between pulsars and supernova remnants, as well as the acquisition of high spatial velocities by pulsars during their birth. __________ Translated from Astrofizika, Vol. 49, No. 1, pp. 103–110 (February 2006).     

The cooling of liquefying hot white dwarfs

The consequences of gas-liquid phase transitions in the core of hot white dwarf stars are discussed. Expressions for the latent heat and the liquefaction curveT _l =T _l (Q) are obtained. Then amodel for a hot white dwarf is introduced and the corresponding liquefaction sequences are built on the H-R diagram; relations luminosity-central temperature and effective temperature-central temperature are also given for liquefying white dwarfs.Finally the cooling curves are obtained for such stars taking into account the effect of latent heat emission.Our results seem to suggest a possible identification of the central stars of planetary nebulae as hot liquefying white dwarfs.     

A symplectic mapping model for the 3/4 exterior

We present a symplectic mapping model to study the evolution of a small body at the 3/4 exterior resonance with Neptune, for planar and for three dimensional motion. The mapping is based on the averaged Hamiltonian close to this resonance and is constructed in such a way that the topology of its phase space is similar to that of the Poincaré map of the elliptic restricted three-body problem. Using this model we study the evolution of a small object near the 3/4 resonance. Both chaotic and regular motions are found, and it is shown that the initial phase of the object plays an important role on the appearance of chaos. In the planar case, objects that are phase-protected from close encounters with Neptune have regular orbits even at eccentricities up to 0.44. On the other hand objects that are not phase protected show chaotic behaviour even at low eccentricities. The introduction of the inclination to our model affects the stable areas around the 3/4 mean motion resonance, which now become thinner and thinner and finally at is=10° the whole resonant region becomes chaotic. This may justify the absence of a large population of objects at this resonance.     

The magnetic field of a rotating cloud and magneto-rotational explosions

The contraction of a massive rotating plasma cloud with the magnetic field perpendicular to the axis of rotation and extending to infinity is considered. At some stage the contracting cloud reaches a state of dynamic quasi-stationary equilibrium. The change of the magnetic field in the cloud atmosphere before its arrival at the quasi-stationary state (stage I) and also in the process of quasi-equilibrium (stage II) are studied.At stage I an essential change of the external magnetic field geometry occurs, namely the formation of zero (neutral) lines and the transformation of the field into a quasi-radial one. Given certain conditions, the reconnection of the field lines in neutral X-type points may occur with the formation of closed loops. In this case the flux of field lines, which connect the contracting cloud with infinity, decreases asymptotically as (R/R _i)^2/3, whereR/R _i is the ratio of the present radius to initial one.After the cloud arrives at the state of dynamic equilibrium (stage II) a considerable increasing of the magnetic field occurs due to twisting of the field lines by rotation. The field strength increases up to some threshold after which instability suddenly occurs. As a result of cumulation occurring in the zero-line direction, and the subsequent dynamic dissipation, the ejection of relativistic particles and plasma in both directions along the rotational axis takes place. The magnetic field restores itself rapidly due to the continual twisting and this leads to the appearance of repeated explosions.The tension of the magnetic field lines as well as plasma outflow carry away the angular momentum. Its diminution determines the rate of secular gravitational contraction. During the contraction the rotational energy increases, so that recurrent bursts, being of magneto-rotational nature are based, finally, on the gravitational energy reservoir.According to our calculations of the time-interval for repetition of explosions, the energy output and certain other parameters, we are able to explain repeated bursts in the nuclei of galaxies and quasars observed, in particular, in the appearance of radio-variability.Extended version of the paper read at All-Moscow Astrophysical Seminar in Sternberg Astronomical Institute 3rd April 1969.     

The critical inclination in artificial satellite theory

Certain it is that the critical inclination in the main problem of artificial satellite theory is an intrinsic singularity. Its significance stems from two geometric events in the reduced phase space on the manifolds of constant polar angular momentum and constant Delaunay action. In the neighborhood of the critical inclination, along the family of circular orbits, there appear two Hopf bifurcations, to each of which there converge two families of orbits with stationary perigees. On the stretch between the bifurcations, the circular orbits in the planes at critical inclinmation are unstable. A global analysis of the double forking is made possible by the realization that the reduced phase space consists of bundles of two-dimensional spheres. Extensive numerical integrations illustrate the transitions in the phase flow on the spheres as the system passes through the bifurcations.A delicacy so very susceptible of offence...—Hester Lynch PIOZZI,Observations and Reflections made in the Course of a Journey through France, Italy and Germany (1789)NAS/NRC Postgraduate Research Associate in 1984–1985.     

New observations of coronal explosions and their interpretation

We examined five flares, observed by the Hard X-Ray Imaging Spectrometer aboard the Solar Maximum Mission, for the occurrence of coronal explosions and found that these occur only if (a) the flare shows distinct single impulsive hard X-ray bursts and (b) it shows upward (convective) motions during the initial part of the impulsive phase. Coronal explosions are therefore explained as a manifestation of plasma streaming laterally out of the flare kernel(s). There is some evidence that streaming occurs into a number of cylindrical fluxtubes which spread over a larger area, thus supporting the spaghetti-bundle model for the flaring region.     

Method for the determination of the distribution function for the mean frequency of supernova explosions

A method is suggested for the determination of the distribution function for the mean frequency of supernova explosions, which is similar to the Ambartsumian method for the determination of the distribution function for the mean flare frequency of flare stars. This method has not been applied because of the lack of the required data.Translated fromAstrofizika, Vol. 39, No. 4, pp. 561–566, November, 1996.     

Mass accretion by the nuclei of disk galaxies,II

Repeated explosions in the nuclei of galaxies are now accepted as observationally established phenomena. Each explosion leads to the ejection of gas from the central region of a galaxy with velocities depending on the strength of the explosive event. In the process the nucleus temporarily becomes gas-deficient. It is suggested that the mass los is replenished by the accretion of the mass which is shed by those evolved stars in the galactic bulge that possess relatively low rotational velocities. The gas to be accreted is assumed to be magnetized. In the present model, the accretion rate has been assumed to be a function of both radial distance and time. The cross-radial equation of motion has been solved to derive the expression for the rotational velocity which is found to bealmost linear with the radial distance from the centre. The radial equation has been solved to calculate the time-scale over which the nucleus accumulates sufficient mass to undergo instability and suffer explosion. The calculated time-scale range from few multiples of 10⁷ to a few multiples of 10⁸ yr. This range agrees very well with that as has been suggested on the basis of observation in the case of our own Galaxy.     

Long Period (0.9–5.5 Year) Oscillations in Surface Spherical Harmonics of Sunspot Longitudinal Distributions

The temporal changes in the two-dimensional patterns of sunspot groups, spanning 125 years (1650 Carrington Rotations), were previously analyzed using surface spherical harmonics (SSHs) (Juckett, 2003) in an attempt to quantify properties of the active longitudes among sunspot distributions. Common trends in the oscillations of both the amplitudes and spatial phases of sectoral combinations of SSHs were examined. The amplitude analysis revealed strong evidence for the second and third harmonics of the 11-year cycle across all SSHs, plus evidence for other structured variations spanning both longer and shorter time scales. In this report, temporal oscillations above the second harmonic reveal a dispersion relationship with respect to order, m, in the m = l and m = l–1 SSH modes. Furthermore, the relationship between amplitude and abrupt spatial phase transitions for these oscillations is consistent with the behavior of standing waves. Under this assumption, each standing-wave half-cycle is identified by spatial phase transitions between and π. This was used to convert the SSH amplitude series for each mode from a rectified version of the standing wave to an estimate of the full cycle. Spectral analysis yielded a dispersion relation over the SSH order range m = 1 to m = 18 spanning the cycle periods from the 11-year solar cycle down to that of the well-documented, but ill-understood 1.3 and 1.8 year quasi-periodic cycles of the quasi-biennial oscillation. Examination of the spatial phase patterns of the SSH modes suggests that the longitudinal variations in sunspot clustering are a complex phenomena with patterns occurring in several time scales. The standing wave trait of the SSH modes may offer evidence uniting the dynamo waves in the convective zone to interfacial oscillations in the tachocline.