Influence Of Radiation Pressure Research Articles

Stability of triangular points in the generalised photogravitational restricted three-body problem with variable mass

The stability of triangular points under the influence of radiation pressure of the bigger primary, oblateness of the smaller primary and variation in mass of the third infinitesimal body has been investigated. It is found that these points are stable for 0 < &#956 < &#956c, and unstable for &#956c < &#956 < ½ . It is also seen that the range of stability decreases due to radiation pressure, oblateness and variation in mass of the respective body. JONAMP Vol. 11 2007: pp. 287-294

Dust measurements at the edge of the solar system

We discuss possible measurement techniques and observation strategies for the detection of interstellar dust particles from spacecraft which travel to the boundaries of the solar system. Large interstellar dust particles as well as dust from Kuiper belt objects will be measured within the heliosphere. The radial speed that is required for an Interstellar Probe mission is favorable for detection methods that are based on the impact ionization of dust particles. This also allows to obtain information about the dust elemental composition. The dust fluxes depend on the influence of radiation pressure, solar gravity, and Lorentz forces on the interstellar dust as well as on the production and evolution of dust from Kuiper belt objects. All the listed effects are correlated to the dust properties and hence allow for a comparison to models that are obtained from astronomical studies. The majority of interstellar dust particles of sizes below 0.1 μm are deflected from entering the heliosphere. They will be measured beyond the heliopause. We use a simple model of the heliospheric transition region to calculate the velocity distributions of these interstellar grains in the neighborhood of the heliosphere. Different assumptions about the interstellar magnetic field and the structure of the plasma flow are considered. We find that the distributions are sensitive to the structure of the heliospheric transition region, in particular to the presence of a sharp bow shock.

Influence of radiation pressure and wind momentum on mass transfer in massive binaries

We perform radiation hydrodynamics simulations of mass transfer in close and massive binary systems, focusing especially on the impact of radiation pressure and wind momentum from the two luminous stars that compose the system. We find that for the large mass transfer rates important for the evolution of such binary systems (of the order of 10–3M⊙yr–1), the light and wind momenta are too low to affect the behaviour of the dense gas stream ejected by the Roche Lobe filling component. In particular, the presence of a wind-wind collision between the two stars has no effect on the gas stream dynamics.

ESCAPE OF PARTICLES ORBITING ASTEROIDS IN THE PRESENCE OF RADIATION PRESSURE THROUGH SEPARATRIX SPLITTING

We study the motion of grains in orbit around asteroids under the influence of radiation pressure originating in the flux of solar photons. Of interest is the possibility of initially bound grains becoming unbound and leaving the vicinity of the asteroid. The analysis extends the two-degree-of-freedom results of (Dankowicz, 1995) to three-degree-of-freedom motions. In particular, we use a Melnikov-type approach for finding transversal points of intersection between high-dimensional perturbed stable and unstable manifolds. As a consequence, the system is shown to be nonintegrable and the resulting homoclinic tangles are suggested as a means for phase space transport along resonance layers, so-called Arnol'd diffusion. We discuss the implications of the diffusion on the depletion of asteroid-bound particles and attempt to estimate the diffusion rate for physical comparison. For particular values of physical parameters the time scale is shown to be on the order of hundreds of orbital revolutions of the asteroid around the sun.

Dynamics of the Leonid Meteoroid Stream: a Numerical Approach

AbstractWe have simulated the evolution of the Leonid stream via numerical integration of 3 million test particles ejected from 55P/Tempel-Tuttle during five perihelion passages of that comet. Using the Whipple ejection velocity formula and a random ejection spread in true anomaly about the parent comet orbit inside 2.3 AU, we have followed the subsequent evolution of Leonid meteoroids differing by over 5 orders of magnitude in mass under the influence of radiation pressure and planetary perturbations. By comparing the model predictions of Leonid activity on a year by year basis with the available observations we have attempted to determine roughly the time of ejection associated with each Leonid storm occurrence and model the observed mass distribution. On the basis of the demonstrated accuracy of the model we make predictions regarding times of peak activity and relative strengths for the Leonid returns for each year during the latter part of the 1990s.

The Split Nucleus of Comet Wilson (C/1986 P1 = 1987 VII)

We present CCD observations of Comet Wilson (C/1986 P1 = 1987 VII) from 26 nights during the time period 1986 October to 1991 February, which brackets perihelion, During the observing run of 1988 February, the comet was observed to have split into two fragments. Our broadband CCD photometry, along with photometry from the International Cometary Quarterly, shows a steady decline in brightness of Comet Wilson post-perihelion, with an outburst between heliocentric distances r = 2.8 and 3.3 AU during 1987 October and November. By r ≈ 7 AU, the fragment had faded with respect to the parent and was no longer centrally condensed. A brightness limit of m R ≈ 25, when the comet was at r = 12.65 AU, constrains the primary nucleus to have a maximum radius between 5 and 7 km, assuming an albedo of 0.04. The accuracy of direct orbital solutions for the parent body and fragment to determine the time of splitting was limited by the presence of significant nongravitational forces and the limited fragment orbital coverage. We used the relative position of the fragment with respect to the parent to calculate a time of splitting which was consistent with the time of the observed outburst. We discuss the possible causes of the splitting. The coma of Comet Wilson was observed to have a surface-brightness profile which fell off as p -1 (characteristic of a canonical steady-state coma under the influence of radiation pressure) for all of the data with the exception of the data taken during 1987 November when the gradient was p -1.3 . This steeper slope was probably caused by the injection of new material into the coma during the outburst. During 1986 October, there was a break in the surface-brightness profile slope which may be interpreted as the distance at which grains are swept into the tail. The profiles suggested grain velocities of a few x 10 2 to 10 m sec -1 for grains between 1 and a few hundred micrometers. Finson-Probstein dust modeling showed that ejection of grains began preperihelion at r gt; 6 AU, peaking near perihelion with a very rapid decline thereafter, with an outburst occurring roughly 170 days post-perihelion. We found no evidence for the existence of discrete features in the coma. Both the primary and fragment nuclei grew redder with time, with the fragment being redder than the parent, consistent with the picture of smaller grains leaving the field of view of the aperture more quickly than larger grains.

The S-DALINAC facility — Operational experience from the accelerator and the experimental installations

The superconducting cw-electron-accelerator S-DALINAC at Darmstadt became operational in January of 1991. It has been used extensively since then to deliver beam to the various experimental installations for nuclear and radiation physics associated with the accelerator. In order to fulfill the requirements of the experiments beam from the nA range up to 40 μA and at energies between 2.5 and 84 MeV could be provided in true cw operation. Energies above 100 MeV could be achieved in accelerator test runs. A special time structure of the electron beam was used for Free Electron Laser (FEL) physics. Spontaneous emission has been observed routinely.The principle of operation of the accelerator is sketched briefly while main emphasis is on specific problems of a superconducting recirculating electron accelerator and their solutions. The operating performance of the superconducting accelerator cavities like the gradients achieved and the amplitude and phase stability of the accelerating field in the presence of microphonic perturbations are discussed in detail including the influence of radiation pressure. For the two recirculating beamlines simple devices were developed to provide variable path lengths for the electron beam in order to optimize the reinjection phase for the successive acceleration in the linac.

Self-organization of cosmic radiation pressure instability. II - One-dimensional simulations

The clustering of statistically uniform discrete absorbing particles moving solely under the influence of radiation pressure from uniformly distributed emitters is studied in a simple one-dimensional model. Radiation pressure tends to amplify statistical clustering in the absorbers; the absorbing material is swept into empty bubbles, the biggest bubbles grow bigger almost as they would in a uniform medium, and the smaller ones get crushed and disappear. Numerical simulations of a one-dimensional system are used to support the conjecture that the system is self-organizing. Simple statistics indicate that a wide range of initial conditions produce structure approaching the same self-similar statistical distribution, whose scaling properties follow those of the attractor solution for an isolated bubble. The importance of the process for large-scale structuring of the interstellar medium is briefly discussed.

The atmosphere of 2060 Chiron

An explanation for 2060 Chiron's behavior, which focuses on the influence of Chiron's mass on the development of its dust coma, is presented. It is suggested that dust is entrained by the flow of CO or another gas of similar volatility from an active region. It remains gravitationally bound on orbits confined to a region, roughly 5000 km in extent, that lies between the surface and an exopause imposed by radiation pressure forces. The influence of radiation pressure transforms the initial particle trajectories into satellite orbits with a characteristic period of 20 days and orbital residence time of about 25 revolutions. The particle population in the coma slowly increases, explaining Chiron's photometric behavior.

Search for a narrow annihilation feature correlated with the MeV emission of Cygnus X-1

Strong gamma-ray emission near 1 MeV from Cygnus X-1 observed in the fall of 1979 during the 'gamma 1' period has been interpreted by Liang and Dermer (1988) as thermal emission from a relativistic, pair-dominated region surrounding the black hole. The observed gamma-rays should interact with each other and with X-rays to form electron/positron pairs inside and outside the accretion disk. Because the Eddington limit is reduced by a factor of 1836 in the presence of positrons, some pairs formed inside the disk may also escape the system under the influence of radiation pressure. If these pairs stop in the cold surrounding medium, a narrow 511 keV annihilation feature should be produced. The high resolution gamma 1 spectrum has been examined for such a feature, and some evidence at 1.9 sigma statistical significance for the line is observed with a flux which is generally consistent with theoretical expectations.

Physical properties of hot-star wind

The basic properties of the flow of stellar winds of O-B stars are considered by analyzing the equations of matter flow under the influence of radiation pressure in lines, allowance being made for the kinetic mechanism of plasma heating.

Collisional balance of the meteoritic complex

Taking into account meteoroid measurements by in situ experiments, zodiacal light observations, and oblique angle hypervelocity impact studies, it is found that the observed size distributions of lunar microcraters usually do not represent the interplanetary meteoroid flux for particles with masses ⪅10 −10g. From the steepest observed lunar crater size distribution a “lunar flux” is derived which is up to 2 orders of magnitude higher than the interplanetary flux at the smallest particle masses. New models of the “lunar” and “interplanetary” meteoroid fluxes are presented. The spatial mass density of interplanetary meteoritic material at 1 AU is ∼10 −16g/m 3. A large fraction of this mass is in particles of 10 −6 to 10 −4 g. A detailed analysis of the effects of mutual collisions (i.e., destruction of meteoroids and production of fragment particles) and of radiation pressure has been performed which yielded a new picture of the balance of the meteoritic complex. It has been found that the collisional lifetime at 1 AU is shortest (∼10 4years) for meteoroids of 10 −4 to 1 g mass. For particles with masses m > 10 −5g, Poynting-Robertson lifetimes are considerably larger than collisional lifetimes. The collisional destruction rate of meteoroids with masses m ⪆ 10 −3 g is about 10 times larger than the rate of collisional production of fragment particles in the same mass range. About 9 tons/sec of these “meteor-sized” ( m > 10 −5g) particles are lost inside 1 AU due to collisions and have to be replenished by other sources, e.g., comets. Under steady-state conditions, most of these large particles are “young”; i.e., they have not been fragmented by collisions and their initial orbits are not altered much by radiation pressure drag. Many more micrometeoroids of masses m ⪅ 10 −5g are generated by collisions from more massive particles than are destroyed by collisions. The net collisional production rate of intermediate-sized particles 10 −10g ⪅ m ⪅ 10 −5g is found to be about 16 times larger at 1 AU than the Poynting-Robertson loss rate. The total Poynting-Robertson loss rate inside 1 AU is only about 0.26 tons/sec. The smallest fragment particles ( m ⪅ 10 −10g) will be largely injected into hyperbolic trajectories under the influence of radiation pressure (β meteoroids). These particles provide the most effecient loss mechanism from the meteoritic complex. When it is assumed that meteoroids fragment similarly to experimental impact studies with basalt, then it is found that interplanetary meteoroids in the mass range 10 −10g ⪅ m ⪅ 10 −5g cannot be in temporal balance under collisions and Poynting-Robertson drag but their spatial density is presently increasing with time.

Influence of radiation pressure on the electron-hole drop in germanium

Influence of radiation pressure on the electron-hole drop in germanium

Studies of evolved stars. V - Nucleosynthesis in hot-bottom convective envelopes

view Abstract Citations (157) References (58) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Studies of evolved stars. V. Nucleosynthesis in hot-bottom convective envelopes. Scalo, J. M. ; Despain, K. H. ; Ulrich, R. K. Abstract Convective envelopes fitted to the cores of luminous double shell models have been found to develop high base temperatures, ( ) >c 106 K, during the period between shell flashes. We show that these "hotbottom" envelopes are the result of the increasing influence of radiation pressure on the radiative and adiabatic temperature gradients. Lower limits on the luminosity (Mbol -3.4) and total mass ( l' o) required for the phenomenon are derived; these values depend sensitively on the treatment of the radiative atmosphere and the ionization zones. Light-element nucleosynthesis in hot-bottom envelopes is examined using a convective diffusion model. Large surface 7Li enhancements are produced by the 7Be transport mechanism if the base temperature Tb exceeds 30 x 106 K. Sufficient time before carbon ignition exists for CN processing if Tb > 50 x 106 K, while full CNO processing and hydrogen depletion may occur if Tb > 75 x 106 K. Comparison with observations indicates that nucleosynthesis in hot-bottom envelopes is not the primary cause of the abundance anomalies observed in peculiar red giants, except possibly for the large 13C/12C ratios and lithium enhancements found in some stars. In particular, mixing of triple-a carbon and s-process elements initiated by the helium shell flashes seems to be required in order to satisfy constraints imposed by the observed line and band strengths and luminosities. Subject headings: abundances, stellar - convection - interiors, stellar - late-type stars - nucleosynthesis Publication: The Astrophysical Journal Pub Date: March 1975 DOI: 10.1086/153471 Bibcode: 1975ApJ...196..805S Keywords: Late Stars; Nuclear Fusion; Stellar Evolution; Astronomical Models; Astrophysics; Convection; Giant Stars; Astrophysics full text sources ADS | data products SIMBAD (5) Related Materials (4) Part 1: 1973ApJ...183..151S Part 2: 1973ApJ...184..801S Part 3: 1974ApJ...192..507U Part 4: 1974ApJ...194..361S

The influence of radiation pressure and drag on Saturn's rings

The influence of radiation pressure and drag on the optical thickness of ring C is calculated as a function of the saturnocentric distance. The results are compared with Franklin and Cook's 1958 data. It seems probable that drag exerts more important effects than radiation pressure, at least in inner parts of ring C. The drag effect might also explain the existence of the Cassini division.

The Behaviour of Dust Under the Influence of Radiation Pressure and Gravity

A study was made of the behaviour of dust under the influence of a centrally symmetric source of gravitation and radial light rays according to general relativity. In one approach the motion of the dust is derived by examining a representative test particle scattering the light isotropically in its rest frame (or alternatively absorbing the light or reflecting it back specularly to the source). Consideration is given next to a thin pressure-free spherlcally symmetric shell of dust and its motion is derived directly from the field equations, confining the study of necessity however to specularly reflecting and absorbing dust. The radial motion is fully analysed and conflrmation is found for isotropically scattering and for specularly reflecting dust, for the stabilization effect first found by one of the present authors (Noerdlinnger, Nature; 237: 5349 (1972)). The treatment ls also extended to test particles with nonzero angular momentum about the source. The comparison of the two methods leads to an analysis clarifying the relation between rest mass and active gravitational mass which latter is shown to be a generalization of what has been considered the Hamiltonian of the material in other contexts. (auth)

On the origin and distribution of meteoroids

The influence of collisional and radiative processes on the population of sporadic and shower meteoroids is examined. It is found that the observed distribution of sporadic meteoroids in the photographic and radio ranges is unstable: collisional processes would rapidly change the distribution of these particles if they are not replenished by a source. It is shown that, in order to maintain the distribution of these sporadic meteoroids in a steady-state condition, a source is needed that replaces the sporadic meteoroids destroyed by collisions. The mass distribution of the required source is calculated and found to agree with the distribution of bright radio-shower meteors, provided that the population index α of sporadic meteors (in the photographic and radio ranges) is taken to be α = 13/6. The evolution of the population in a meteor shower under the influence of collisions with sporadic meteoroids is also examined. Since small particles have shorter lifetimes (with respect to collisions) than do larger particles, the population of faint shower meteors is more strongly affected. It is found that the mass distribution of faint radio meteors in the major showers considered here agrees with the results of the analysis, provided that α = 13/6, for sporadic meteors. Taking α = 13/6 therefore provides self-consistency for analysis and observation, thereby providing new evidence favoring the cometary origin of meteors. The rate at which the population of sporadic meteoroids is losing mass is calculated and found to compare favorably with F. L. Whipple's 1967 estimate as well as his estimate of the rate at which comets are injecting meteoritic mass into the solar system. The influence of the Poynting-Robertson effect on the meteoroid mass distribution is found to be minor; collisional processes dominate the evolution of meteoroids in the faint and brighter radio range. The influence of radiation pressure may be profound. By using previous work by Harwit and geometrical optics, it is shown that the smallest masses present in the major meteoroid showers are in the range of 10−6 to 10−10 gram. This is precisely the mass range where a leveling off of the distribution of sporadic meteoroids is indicated by satellite penetration measurements; these measurements are therefore consistent with the cometary origin of sporadic meteoroids. These theoretical results may not apply to particles with masses of 10−12 gram or smaller (i.e., submicron particles, for which details of physical optics become important).

Gas-Dust Interaction in the Accretion of Interstellar Dust by the Sun.

view Abstract Citations References (4) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Gas-Dust Interaction in the Accretion of Interstellar Dust by the Sun. Stephenson, Charles B. Abstract As is well known, the suggestion that the sun's family of comets was acquired by accretion of dust from the interstellar medium encounters a difficulty in the form of the interaction between dust and radiation pressure. If the general nature of the dust is correctly characterized by current views, the solar radiation pressure upon a particle exceeds the gravitational force for a large fraction of the total population of particles. Hence it is of interest to investigate the possibility that the dust can nevertheless be accreted through interaction with the interstellar gas. Approximate calculations have been made to ascertain the behavior of dust particles of the order of 10- cm in diameter, for which p 1.0, in the radiation field of the sun and subject to viscosity effects in the interstellar gas. It is concluded that interaction between gas and such dust particles cannot compensatefor the influence of radiation pressure for a gas density in the unperturbed cloud < 10 atoms/cm3 and for relative velocities of the order of 5 km/sec between star and cloud Much lower velocities favor dust capture more than do the velocities discussed here, but they involve excessive accretion of gas by the sun. Publication: The Astrophysical Journal Pub Date: July 1957 DOI: 10.1086/146385 Bibcode: 1957ApJ...126..195S full text sources ADS |