Suprathermal grains: On intergalactic magnetic fields

Charged dust grains of radiia3×10^–63×10^–5 cm may be driven out of the galaxy due to radiation pressure of starlight. Once clear of the main gas-dust layer, dust grains may then escape into intergalactic space. Such grains are virtually indestructible-being evaporated only during galaxy formation. The dust grains, once injected into the intergalactic medium, may acquire suprathermal energy, thus suprathermal grains in collision with magnetized cloud by the Fermi process. In order to attain relativistic energy, suprathermal grains have to move in and out (scattering) of the magnetic field of the medium. It is now well established that high energy cosmic rays are of the order 10²⁰ eV or more. We have speculated that these high energy (>-10¹⁸ eV) cosmic ray particles are charged dust grains, of intergalactic origin. This is possible only if there exists a magnetic field in the intergalactic medium.     

Cosmic ray origin above 1018 eV: Galactic or extragalactic?

An analysis is made of the implications of assuming that suprathermal dust grains (a3×10⁸ cm) of intergalactic origin may acquire cosmic ray energies as high as 10²⁰ eV. These dust grains may attain suprathermal energy (v _g3×10⁸ cm s^–1) by the Fermi process. Initially the dust grains are accelerated by the radiation pressure against the drag of the ambient gas of the medium, but once these dust grains attain a terminal velocity (U10⁵ cm s^–1), then they may be expelled out of the galactic region into the intergalactic medium and finally acquire high energy     

Intergalactic suprathermal grains

The physical conditions under which suprathermal grains may loose energy and the processes involving the grains (a3×10^–6 cm) destruction are investigated. It is found that the dust grain once attaining the velocityU (10⁵ cm s^–1) may attain suprathermal energy (v _g3×10⁸ cm s^–1) and subsequently may also attain relativistic energy are almost indestructible in the accelerating phase.     

Cosmic gamma-ray burst from intergalactic relativistic dust grains

Charged dust grains of radiia3×10^–63×10^–5 cm may acquire relativistic energy (>10¹⁸ eV) in the intergalactic medium. In order to attain relativistic energy, dust grains have to move in and out (scattering) of the magnetic field of the medium. A relativistic grain of radiusa10^–5 cm with Lorentz factor 10³ approaching the Earth will break up either due to electrostatic charge or due to sputtering about 150100 km, and may scatter solar photons via a fluorescence process. Dust grains may also melt into droplets in the solar vicinity and may contribute towards observed gamma-ray bursts.     

Shock wave effects in solar cosmic ray events

Two low-energy ( 1 MeV) solar proton events which display a gradual intensity increase to a maximum near the time of an SSC, followed by an abrupt, large decrease, are interpreted in terms of a population of cosmic rays which are swept ahead of an interplanetary shock wave. A model which describes the variation with time of intensity and anisotropy at the Earth is developed using a Monte Carlo technique which traces the histories of particles released impulsively at the Sun. A good fit to each of the profiles observed at 0.6 to 0.9 MeV proton energies is obtained with a diffusion coefficient 2 × 10²⁰ cm² s^–) = 13.46 - 2.99 sin²1 and a near perfect shock reflector.Now at University of California, LASL, Los Alamos, New Mexico.     

On the production of suprathermal grains

The physical conditions under which suprathermal grains can be produced when they are accelerated by radiation pressure against the drag of ambient gas are investigated. It is found that dust grains may attain a terminal velocityU (=10⁵ cm s^–1) in most regions and move out of the midplane of the source region about a distance |z|100 pc. Once clear of the main gas/dust layer the dust grains (a3×10^–6 cm) may then attain suprathermal energy (V _g 3×10⁸ cm s^–1) by the Fermi process.     

Production of metagalactic X-rays by relativistic dust grains

The relativistic dust grains which may be responsible for ultra-high energy cosmic rays, as suggested by the present author, interact with the cosmic black-body radiation. This results in the energy loss of the relativistic dust grains, so that their energy spectrum is cut-off at the Lorentz factor as large as 2×10³ (0.1/a), wherea is the grain radius. The black-body radiation is scattered and absorbed by the dust grains. The photons scattered and reemitted contribute to metagalactic X-rays. The X-ray intensity estimated is comparable to the observed one in the soft X-ray region.     

Spatial density fluctuations in the radiation era of the Universe

It is shown that in the radiation era of the Universe spatial temperature fluctuations (T/T)<10^–5 in the cosmic plasma lead to huge changes of the density up to (/)10⁴. This effect results from the fact that the cosmic plasma in the radiation era can be considered as a general relativistic Boltzmann gas which is found in the very vincinity of equilibrium.     

The interrelationship between cosmic dust and the microwave background

Attention is given to the radiation of microwaves by charged dust in space. Presently-used particle distributions do not restrict the presence in space of large numbers of small (r<10^–6 cm) silicate grains, but it is shown that such densities (10^–25–10^–26 g cm^–3) of small grains would produce a microwave background with an energy density of the same order of magnitude as the energy density of the (presumed) cosmological 3 K background. Limits set by the isotropy of the latter are: (HI clouds)10^–26, (Galactic plane)10^–30, (Halo)10^–32, (Local Group)10^–34 g cm^–3. These limits imply that either there is a cutoff in particle distributions atr10^–6 cm, or that the density of silicate grains in space has been generally overestimated, or that cosmic rays have broken up a lot of grains so that they now form a population of grains of very small size (10^–7 cm) which are difficult to detect by conventional methods. One way to look for the latter population is by studying expected distortions of the 3 K spectrum to the short wavelength side of the portion hitherto observed (grains may have a size distribution able to give an approximate black-body curve for radiation from larger grains of 10^–6 cm size), and by testing the effective energy density of the 3 K field in other galaxies.     

Search for relativistic companions in ‘non-X-ray’ binary systems

Consideration is given to a search for relativistic objects in massive close binary systems without strong X-ray emission (L _x <10³⁴ erg s^–1). It is pointed out that, according to the present-day theory on the evolution of massive close binaries, the number of neutron stars and black holes in non-X-ray binary systems must be 100 times the number of the known X-ray binaries comprising OB supergiant stars; that is why, in studying non-X-ray binary systems, the chances are to detect about a hundred of black holes in the Galaxy.Criteria are formulated for the relativistic nature of companions in the binary systems, such as high spatial velocity values and height Z over the galactic plane for OB stars (runaway stars) and for Wolf-Rayet stars. As reported by Tutukov and Yungelson (1973), as well as by van den Heuvel (1976), the presence of ring-type nebulae can serve as another indication of a relativistic nature of companions in the case of Wolf-Rayet stars.Data are collected on Wolf-Rayet stars with low-mass companions (Table I), which can be relativistic objects accreting within a strong stellar wind from Wolf-Rayet stars. Presented are new findings in respect of spectral examination of the runaway OB-stars (Table II), bringing together data on eight OB stars which can represent binary systems with relativistic companions (Table III).A list of 28 OB-stars (Table IV) which offer a good chance for finding relativistic companions is given.     

Gas,dust and molecules in the Galaxy

The relative abundances of cool neutral hydrogen, carbon monoxide and formaldehyde are studied using all the available observational data in the literature. The obtained mean valuesN _{H 1}/ ,N _{H 1}/N _CO,N _CO/ are approximately constant in the dark clouds of the solar neighbourhood and in the distant molecular clouds.The observed correlationsN _CO,A _v and ,A _v show that formaldehyde can also be used as an indicator of molecular hydrogen. The ratioN H₁/A _v depends on densities and decays considerably in the ranges of visual absorptions in which the molecules become detectable (A _v 2 mg); an average of /N _{H 1}10 is calculated for the dense dark clouds.Indications of systematic temperature gradiens T/A _v are found for formaldehyde and neutral hydrogen inside the dark clouds, and qualitative comparisons are made with theoretical quantum mechanics calculations.The observed carbon monoxide and formaldehyde abundances, the free electron layer in the Galaxy, the distribution of neutral hydrogen in different states are only compatible if an ionization rate of 10^–16 is accepted, provided presumably by 2 MeV protons of cosmic radiation.Three main states for neutral hydrogen and dust are identified from different kinds of observational data (21 cm line in emission, absorption in galactic radio sources and self-absorption in the hot gas background): (1) a homogeneous intercloud stratum of tenuous gas and dust with a galactic halfwidth of 350 pc and mean parametersn _H=0.2 atom cm^–3, spin temperatureT _s 10000 K andn _d 0.3 mg kpc^–1; (2) cool gas and dust concentrated in spiral features with a galactic half-width of less than 100 pc, probably forming clouds with diffuse and indefinite limits, with mean parametersn _H2 atom cm^–3,T _s <1100 K (probable average,T _s =135 K) andn _d 3 mg kpc^–1; (3) dense gas and dust clouds with a mean diameter of 7 pc and mean parametersn _H700 atom cm^–3 (90% in a molecular state),T _s 63 K andn _d 1 mg pc^–1 on which molecules as CO and H₂CO are formed.The application of the Jeans criteria for gravitational instability shows that the dense clouds are gravitationally bound while the gas in the intermediate state (2) can be protected against collapse by the total internal energy in the medium increasing due to cosmic rays and the magnetic field in the Galaxy.The observed velocity halfwidths and galacticZ-halfwidths in states (1) and (2) are compatible with a total mass density in the galactic layer of 90M pc^–2 (gas plus stars) according to the barometric equation.The relative abundancesN _{H 1}/N _CO, calculated from C¹²O and C¹³O data and comparisons with studies in the 21 cm emission line, show that the antenna temperatureT _A ⁺ in the 2.6 mm line of C¹²O is a good indicator of the cool gas densities in the Galaxy. The possible application of this for studies in galactic structure is discussed and hypothetical distributions of carbon monoxide in the zones outside the galactic planeB=0° are presented.From a synthesis based on the results obtained, a cycle is postulated for the neutral hydrogen in the Galaxy: condensation and cooling of gas molecular formation gravitational collapse and star formation gas dissipation and heating by cosmic rays and UV radiation.     

Индуцированное комптоновское рассеяние изотропного излучения релятивистскими электронами

, kT _b mc ² . . , , . E ^–5, - E ², mc ²(kT /mc ²)^1/7. , (>2.10⁵ cm ^–3) . , -, , .     

The possibility of transition radiation in planetary nebulae

A new concept —the Paradox of Nebula IC4997 — is the main subject of the present article. The essence of this paradox arises when the variations of the intensities of forbidden lines 4363 [Oiii] andN ₁+N ₂ [Oiii] take place not in unison as is predicted by the classical theory. An attempt is made to solve this paradox, suggesting the possibility both of spontaneous appearance of relativistic electrons in the nebula and the generation of so-calledtransition radiation as a result of electrodynamic interaction of these electrons with dust particles in nebula. The parameters of relativistic electrons and power of transition radiation are obtained. The problems which need further examination are also enumerated.     

Nucleation in novae

We consider the possibility that dust grains in novae could nucleate on ions. We examine how different ejected masses and different elemental abundances effect the availability of nucleation centres, and we show how this model could explain why only novae of intermediate speed classes form dust.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.     

The dust grains in the coma of Comet West

The observed variation of reddening as function of the heliocentric distance and the spatial variation of reddening within the coma of Comet West in the visual wavelength range have been considered to infer the properties of the cometary dust grains. The relevant model incorporates the variation in the size distribution function as well as the composition of the spherical grains. The real part of the complex index of refraction (m = m – im) is chosen such thatm = 1.6. The imaginary part is required to vary from m = 0.2 to 0.05 over the wavelength range 0.4 to 0.7 m. This choice of refractive index corresponds to dirty silicate grains. As a by-product, the model also satisfies the observed polarization and albedo for the Comet West.     

Einstein-like field equations with conserved source and decreasing ∧ term; Their cosmological consequences

The consequences of a cosmological term varying asS ^–2 in a spatially isotropic universe with scale factorS and conserved matter tensor are investigated. One finds a perpetually expanding universe with positive and gravitational constantG that increases with time. The hard equation of state 3P>U (U mass-energy density,P scalar pressure) applied to the early universe leads to the expansion lawSt (t cosmic time) which solves the horizon problem with no need of inflation. Also the flatness problem is resolved without inflation. The model does not affect the well known predictions on the cosmic light elements abundance which come from standard big bang cosmology.In the present, matter dominated universe one findsdG/dt=2H/U (H is the Hubble parameter) which is consistent with observations provided <10^–57 cm^–2. Asymptotically (S) the term equalsGU/2, in agreement with other studies.     

Comparison of large-scale structures and velocities in the local universe

Comparison of the large-scale density and velocity fields in the local universe shows detailed agreement, strengthening the standard paradigm of the gravitational origin of these structures. Quantitative analysis can determine the cosmological density parameter, , and biasing factor,b; there is virtually no sensitivity in any local analyses to the cosmological constant,. Comparison of the dipole anisotropy of the cosmic microwave background with the acceleration due to theIRAS galaxies puts the linear growth factor in the range ^0.6 /b = 0.6 _–0.3 ^+0.7 (95% confidence). A direct comparison of the density and velocity fields of nearby galaxies gives = 1.3 _–0.6 ^+0.7 , and from nonlinear analysis the weaker limit > 0.45 forb > 0.5 (again 95% confidence). A tighter limit, > 0.3 (4–6), is obtained by a reconstruction of the probability distribution function of the initial fluctuations from which the structures observed today arose. The last two methods depend critically on the smooth velocity field determined from the observed velocities of nearby galaxies by thePOTENT method. A new analysis of these velocities, with more than three times the data used to obtain the above quoted results, is now underway and promises to tighten the uncertainties considerably, as well as reduce systematic bias.     

Interaction of relativistic dust grains with the solar radiation field

The effects of the solar radiation field on the propagation of relativistic dust grains are evaluated. It is concluded that relativistic iron grains with energies 10¹⁹ eV will melt in the solar radiation field before they reach the Earth's orbit around the Sun. However iron grains with lower energies will reach the Earth's orbit but grains travelling from the direction of the Sun will melt. This directional anisotropy or fingerprint may be used to search for relativistic dust grains in the primary cosmic rays. The fact that no significant solar system anisotropy has been detected places constraints on the hypothesis that the initiating particles of the extensive air showers are relativistic iron grains.     

Оπорная селенодезическая система координат по гелиометрическим наБлюдениям луны В казани

, 1969–1975 .., 32 . , .     

A role of cosmic rays in generation of radio and optical radiation by plasma mechanisms

The radiation of ultrarelativistic particles is examined in a quasi-uniform magnetic field superimposed by a wide spectrum of magnetic, electric, and electron density inhomogeneities created in a turbulent plasma. The radiation spectrum from a particle of a given energy is shown to acquire a high-frequency power-law tail with the same spectral index as the index of small-scale turbulence. For a power-law spectrum of ultrarelativistic electrons, dN()/d ~ ^–, with a cut-off at some energy _max, the radiation spectrum consists of a few power-law ranges; the radiation intensity may suffer jumps at frequencies which separate these ranges.In the high-frequency range the spectral index is determined by small-scale magnetic and electric fields. At intermediate frequencies the main contribution comes from the synchrotron radiation in a large-scale field; the radiation spectrum has an index =(–1)/2. The same index may be produced by large-scale Langmuir waves. At lower frequencies the radiation spectrum increases owing to the transition radiation caused by electron density fluctuations; in this case the spectral index is equal to +1–.The possibility of diagnostics of high-frequency cosmic plasma turbulence from radiation of high-energy particles is discussed. It is shown that the proposed theory may explain some features in the spectra of several cosmic objects.