Poynting-Robertson Drag Research Articles

Momentum transfer to interplanetary dust from the solar wind

Solar-wind particles striking dust grains in orbit around the sun exert not only a repulsive force on the grains, but also a drag force, called the plasma or pseudo Poynting-Robertson (PR) effect, which limits their dynamical lifetimes. To better understand the dynamical evolution of interplanetary dust, we study the momentum transfer from the solar wind to interplanetary dust taking into account the passage of impinging particles through the grains. The pseudo PR drag is one of the most important perturbations for the dynamics of interplanetary dust of any sizes. However, previous studies underestimated the lifetimes of small grains by overestimating the acting solar-wind forces. Our study also provides the velocity distribution of neutralized solar-wind particles after passage through a grain along with some implications for the generation of pick-up ions by solar-wind interaction with dust grains.

On the dynamical consequences of the Poynting-Robertson drag caused by solar wind

To correctly take into account the solar wind drag equations for secular variations in the meteoroid orbital semimajor axes and eccentricities were obtained. The equations are similar to those derived for the Poynting- Robertson radiation drag (Wyatt and Whipple 1950). An estimation for the Geminid meteoroid stream shows that the ratios of corpuscular to radiation drags are 0.4 – 0.7 for particles of size , i.e. the effect is much stronger than was assumed before.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Light-scattering models applied to circumstellar dust properties

Radiation pressure force, Poynting–Robertson effect, and collisions are important to determine the size distribution of dust in circumstellar debris disks with the two former parameters depending on the light-scattering properties of grains. We here present Mie and discrete-dipole approximation (DDA) calculations to describe the optical properties of dust particles around β Pictoris, Vega, and Fomalhaut in order to study the influence of the radiation pressure force. We find that the differences between Mie and DDA calculations are lower than 30% for all porosities. Therefore, Mie calculations can be used to determine the cut-off limits which contribute to the size distribution for the different systems.

The Poynting-Robertson Effect

The purpose of this article is to present a simple apparatus for demonstrating the Poynting-Robertson (PR) effect, which is of interest in planetary astronomy. Our setup involves linear rather than rotational motion, and only needs the standard air-track apparatus that is commonly used in freshman labs to verify conservation of linear momentum.

Why Are Massive Black Holes Small in Disk Galaxies?

A potential mechanism is proposed to account for the fact that supermassive black holes (SMBHs) in disk galaxies appear to be smaller than those in elliptical galaxies in the same luminosity range. We consider the formation of SMBHs by radiation drag (the Poynting-Robertson effect), which extracts angular momentum from interstellar matter and thereby drives the mass accretion onto a galactic center. In particular, we quantitatively scrutinize the efficiency of radiation drag in a galaxy composed of bulge and disk, and we elucidate the relation between the final mass of SMBH and the bulge-to-disk ratio of the galaxy. As a result, it is found that the BH-to-galaxy mass ratio, MBH/Mgalaxy, decreases with a smaller bulge-to-disk ratio, because of the effects of geometrical dilution and opacity, and is reduced maximally by 2 orders of magnitude, resulting in MBH/Mgalaxy ≈ 10-5. In contrast, if only the bulge components in galaxies are focused, the BH-to-bulge mass ratio becomes MBH/Mbulge ≈ 10-3, which is similar to that found in elliptical galaxies. Thus, it turns out that the mass of an SMBH primarily correlates with a bulge, not with a disk, consistent with observational data.

Some comments on the F ring-Prometheus–Pandora environment

The system formed by the F ring and two close satellites, Prometheus and Pandora, has been analysed since the time that Voyager visited the planet Saturn. During the ring plane crossing in 1995 the satellites were found in different positions as predicted by the Voyager data. Besides the mutual effects of Prometheus and Pandora, they are also disturbed by a massive F ring. Showalter et al. [Icarus 100 (1992) 394] proposed that, the core of the ring has a mass which corresponds to a moonlet varying in size from 15 to 70 km in radius which can prevent the ring from spreading due to dissipative forces, such as Poynting–Robertson drag and collisions. We have divided this work into two parts. Firstly we analysed the secular interactions between Prometheus–Pandora and a massive F ring using the secular theory. Our results show the variation in eccentricity and inclination of the satellites and the F ring taking into account a massive ring corresponding to a moonlet of different sizes. There is also a population of dust particles in the ring in the company of moonlets at different sizes [Icarus 109 (1997) 304]. We also analysed the behaviour of these particles under the effects of the Poynting–Robertson drag and radiation pressure. Our results show that the time scale proposed for a dust particle to leave the ring is much shorter than predicted before even in the presence of a coorbital moonlet. This result does not agree with the confinement model proposed by Dermott et al. [Nature 284 (1980) 309]. In 2004, Cassini mission will perform repeated observations of the whole system, including observations of the satellites and the F ring environment. These data will help us to better understand this system.

Electromagnetic Radiation and Motion of a Particle

We consider the motion of uncharged dust grains of arbitrary shape including the effects of electromagnetic radiation and thermal emission. The resulting relativistically covariant equation of motion is expressed in terms of standard optical parameters. Explicit expressions for secular changes of osculating orbital elements are derived in detail for the special case of the Poynting-Robertson effect. Two subcases are considered: (i) central acceleration due to gravity and the radial component of radiation pressure independent of the particle velocity, (ii) central acceleration given by gravity and the radiation force as the disturbing force. The latter case yields results which may be compared with secular orbital evolution in terms of orbital elements for an arbitrarily shaped dust particle. The effects of solar wind are also presented.

A Dissipative Mapping Technique for theN-Body Problem Incorporating Radiation Pressure, Poynting-Robertson Drag, and Solar Wind Drag

By implementing a version of the dissipative mapping technique introduced by R. Malhotra, we have developed a new integration code for the N-body problem that incorporates the effects of radiation pressure, Poynting-Robertson (P-R) drag, and solar wind drag. The advantage of employing the dissipative mapping technique is that it modifies the basic N-body symplectic integration algorithm developed by Wisdom & Holman to allow certain nongravitational effects to be modeled and therefore retains the speed of execution common to codes based upon this algorithm. To achieve this, we have adapted the dissipative mapping technique to the requirements of the forces being modeled. We present the results of tests that demonstrate the suitability of this new dissipative integration code for investigating the dynamical behavior of micron-sized dust particles in heliocentric orbits in the solar system and, more generally, of particles in exosolar planetary systems where the dominant nongravitational perturbations to the particles' astrocentric orbits are due to the effects of radiation pressure, P-R drag, and solar wind drag.

Interactions of Dust Grains with Coronal Mass Ejections and Solar Cycle Variations of the F‐Coronal Brightness

The density of interplanetary dust increases sunward to reach its maximum in the F corona, where its scattered white-light emission dominates that of the electron K corona above about 3 Solar Radius. The dust will interact with both the particles and fields of antisunward propagating coronal mass ejections (CMEs). To understand the effects of the CME/dust interactions we consider the dominant forces, with and without CMEs. acting on the dust in the 3-5 Solar Radius region. Dust grain orbits are then computed to compare the drift rates from 5 to 3 Solar Radius. for periods of minimum and maximum solar activity, where a simple CME model is adopted to distinguish between the two periods. The ion-drag force, even in the quiet solar wind, reduces the drift time by a significant factor from its value estimated with the Poynting-Robertson drag force alone. The ion-drag effects of CMEs result in even shorter drift times of the large (greater than or approx. 3 microns) dust grains. hence faster depletion rates and lower dust-pain densities, at solar maxima. If dominated by thermal emission, the near-infrared brightness will thus display solar cycle variations close to the dust plane of symmetry. While trapping the smallest of the grains, the CME magnetic fields also scatter the grains of intermediate size (0.1-3 microns) in latitude. If light scattering by small grains close to the Sun dominates the optical brightness. the scattering by the CME magnetic fields will result in a solar cycle variation of the optical brightness distribution not exceeding 100% at high latitudes, with a higher isotropy reached at solar maxima. A good degree of latitudinal isotropy is already reached at low solar activity since the magnetic fields of the quiet solar wind so close to the Sun are able to scatter the small (less than or approx. 3 microns) grains up to the polar regions in only a few days or less, producing strong perturbations of their trajectories in less than half their orbital periods. Finally, we consider possible observable consequences of individual CME/dust interactions. We show that the dust grains very likely have no observable effect on the dynamics of CMEs. The effect of an individual CME on the dust grains, however, might serve as a forecasting tool for the directions and amplitudes of the magnetic fields within the CME.

The capture of interstellar dust: the pure electromagnetic radiation case

Possible capture of arbitrarily shaped interstellar dust due to the action of electromagnetic radiation and gravitational forces of the Sun is investigated. While earlier investigations have used the Poynting–Robertson effect as a representation of the electromagnetic radiation force, we also use generalized electromagnetic radiation force applicable both to spherical and non-spherical particles. It is shown that the capture depends not only dust particle size and chemical composition, but also on particle shape. Particles with effective radii less than approximately 0.2 μm are blown off from the Solar System due to action of radiation pressure. Large submicron and small micron-sized non-spherical particles are captured at much larger distances from the Sun than spherical particles. As a consequence, realistically shaped particles can survive in the Solar System, while spherical ones of the same size vanish (sublimate or hit the Sun).

Probing Structures of Distant Extrasolar Planets with Microlensing

Planetary companions to the source stars of a caustic-crossing binary microlensing events can be detected via the deviation from the parent light curves created when the caustic magnifies the starlight reflecting off the atmosphere or surface of the planets. The magnitude of the deviation is δp ~ pρ, where p is the fraction of starlight reflected by the planet and ρp is the angular radius of the planet in units of the angular Einstein ring radius. Because of the extraordinarily high resolution achieved during the caustic crossing, the detailed shapes of these perturbations are sensitive to fine structures on and around the planets. We consider the signatures of rings, satellites, and atmospheric features on caustic-crossing microlensing light curves. We find that, for reasonable assumptions, rings produce deviations of the order of 10%δp, whereas satellites, spots, and zonal bands produce deviations of the order of 1%δp. We consider the detectability of these features using current and future telescopes and find that, with very large apertures (>30 m), ring systems may be detectable, whereas spots, satellites, and zonal bands will generally be difficult to detect. We also present a short discussion of the stability of rings around close-in planets, noting that rings are likely to be lost to Poynting-Robertson drag on a timescale of the order of 105 yr, unless they are composed of large (1 cm) particles or are stabilized by satellites.

Joint Consequences of the Poynting-Robertson Effect and Planetary Perturbations in the Restricted Plane Circular Three-Body Problem

The problem on the motion of a dust particle in the Solar system when the perturbations from a single planet, the light pressure, and the Poynting–Robertson effect are simultaneously taken into account is solved by qualitative methods in terms of the restricted plane circular three-body problem. Only two cases of dynamical behavior of the particle have been found to be possible when it falls into the 1 : 1 resonance region. Either the particle is captured into the sphere of action of the planet and eventually falls to the latter or it passes through the resonance zone into a region closer to the Sun. For a random scatter of particle positions, the probability of the former outcome is comparatively low, of the order of the ratio of the radius of the planet's sphere of action to its orbital radius.

Evolution of Planetesimals in Planetary Debris Disks

Dusty planetary disks can form quickly around young stars and linger, despite the depletion of dust through mechanisms such as Poynting-Robertson drag. Planetesimals in the disk can replenish the dust with an efficiency that depends on their mass and velocity distributions. Here, we describe a numerical program to track the evolution of planetesimals through merging, fragmentation and drag. Our current effort is focused on coupling a Fokker-Planck solver with N-body calculations to follow the detailed behavior of larger planetesimals. Our results demonstrate the importance of gravitational stirring in dust production. Furthermore, stirring by planets larger than Pluto can generate the large scale heights seen in several dusty disks.

The Zodiacal Emission Spectrum as Determined byCOBEand Its Implications

We combine observations from the DIRBE and FIRAS instruments on the COBE satellite to derive an annually averaged spectrum of the zodiacal cloud in the 10-1000 μm wavelength region. The spectrum exhibits a break at ~150 μm that indicates a sharp break in the dust size distribution at a radius of about 30 μm. The spectrum can be fitted with a single blackbody with a λ-2 emissivity law beyond 150 μm and a temperature of 240 K. We also used a more realistic characterization of the cloud to fit the spectrum, including a distribution of dust temperatures representing different dust compositions and distances from the Sun, as well as a realistic representation of the spatial distribution of the dust. We show that amorphous carbon and silicate dust with respective temperatures of 280 and 274 K at 1 AU, and size distributions with a break at grain radii of 14 and 32 μm, can provide a good fit to the average zodiacal dust spectrum. The total mass of the zodiacal cloud is 2-11 Eg (Eg = 1018 g), depending on the grain composition. The lifetime of the cloud, against particle loss by Poynting-Robertson drag and the effects of solar wind, is about 105 yr. The required replenishment rate is ~1014 g yr-1. If this is provided by the asteroid belt alone, the asteroids lifetime would be ~3 × 1010 yr. But comets and Kuiper belt objects may also contribute to the zodiacal cloud.

A Cosmic Battery Reconsidered

We revisit the problem of magnetic field generation in accretion flows onto black holes owing to the excess radiation force on electrons. This excess force may arise from the Poynting-Robertson effect. Instead of a recent claim of the generation of dynamically important magnetic fields, we establish the validity of earlier results from 1977 which show only small magnetic fields are generated. The radiative force causes the magnetic field to initially grow linearly with time. However, this linear growth holds for only a {\it restricted} time interval which is of the order of the accretion time of the matter. The large magnetic fields recently found result from the fact that the linear growth is unrestricted. A model of the Poynting-Robertson magnetic field generation close to the horizon of a Schwarzschild black hole is solved exactly using General Relativity, and the field is also found to be dynamically insignificant. These weak magnetic fields may however be important as seed fields for dynamos.

Radiation Pressure and the Poynting–Robertson Effect for Fluffy Dust Particles

A correct understanding of the dynamical effect of solar radiation exerted on fluffy dust particles can be achieved with assistance of a light scattering theory as well as the equation of motion. We reformulate the equation of motion so that the radiation pressure and the Poynting–Robertson effect on fluffy grains are given in both radial and nonradial directions from the center of the Sun. This allows numerical estimates of these radiation forces on fluffy dust aggregates in the framework of the discrete dipole approximation, in which the first term of the scattering coefficients in Mie theory determines the polarizability of homogeneous spheres forming the aggregates.The nonsphericity in shape turns out to play a key role in the dynamical evolution of dust particles, while its consequence depends on the rotation rate and axis of the grains. Unless a fluffy dust particle rapidly revolves on its randomly oriented axis, the nonradial radiation forces may prevent, apart from the orbital eccentricity and semimajor axis, the orbital inclination of the particle from being preserved in orbit around the Sun. However, a change in the inclination is most probably controlled by the Lorentz force as a consequence of the interaction between electric charges on the grains and the solar magnetic field. Although rapidly and randomly rotating grains spiral into the Sun under the Poynting–Robertson effect in spite of their shapes and structures, fluffy grains drift inward on time scales longer at submicrometer sizes and shorter at much larger sizes than spherical grains of the same sizes. Numerical calculations reveal that the dynamical lifetimes of fluffy particles are determined by the material composition of the grains rather than by their morphological structures and sizes. The Poynting-Robertson effect alone is nevertheless insufficient for giving a satisfactory estimate of lifetimes for fluffy dust grains since their large ratios of cross section to mass would reduce the lifetimes by enhancing the collisional probabilities. We also show that the radiation pressure on a dust particle varies with the orbital velocity of the particle but that this effect is negligibly small for dust grains in the Solar System.

Collisional Cascades in Planetesimal Disks. I. Stellar Flybys

We use a new multiannulus planetesimal accretion code to investigate the evolution of a planetesimal disk following a moderately close encounter with a passing star. The calculations include fragmentation, gas and Poynting-Robertson drag, and velocity evolution from dynamical friction and viscous stirring. We assume that the stellar encounter increases planetesimal velocities to the shattering velocity, initiating a collisional cascade in the disk. During the early stages of our calculations, erosive collisions damp particle velocities and produce substantial amounts of dust. For a wide range of initial conditions and input parameters, the time evolution of the dust luminosity follows a simple relation, L_d/L_{\star} = L_0 / [alpha + (t/t_d)^{beta}]. The maximum dust luminosity L_0 and the damping time t_d depend on the disk mass, with L_0 proportional to M_d and t_d proportional to M_d^{-1}. For disks with dust masses of 1% to 100% of the `minimum mass solar nebula' (1--100 earth masses at 30--150 AU), our calculations yield t_d approx 1--10 Myr, alpha approx 1--2, beta = 1, and dust luminosities similar to the range observed in known `debris disk' systems, L_0 approx 10^{-3} to 10^{-5}. Less massive disks produce smaller dust luminosities and damp on longer timescales. Because encounters with field stars are rare, these results imply that moderately close stellar flybys cannot explain collisional cascades in debris disk systems with stellar ages of 100 Myr or longer.

Orbital Properties of the Arecibo Micrometeoroids at Earth Interception

Using the Arecibo Observatory (AO) 430-MHz Radar we have developed a Doppler technique to measure very precise micrometeor instantaneous velocities directly from the meteor head echo. In addition, a large number of the observed meteoroids show deceleration. With the velocity, the deceleration, and the assumptions of a spherical shape and a mean micrometeoroid mass density, we have obtained estimates of in-atmosphere particle sizes. The size estimate, the MSIS model atmosphere, and the measured deceleration are used to obtain the meteor extra-atmospheric speeds, assuming these particles undergo little mass-loss prior to and during the time we detect them (Janches et al. 2000b, Icarus 145, 53–63). Orbital elements at 1 AU are presented and discussed. These results have not been corrected for perturbation effects such as radiation pressure, Poynting–Robertson drag, attraction by the giant planets, and photoelectric charging effects. So far, over 7700 detections obtained during November 1997 and 3500 during the November 1998 observation campaigns have been analyzed. The observing periods included the Leonids meteor shower, but none of the orbits are recently derived from it. Out of these detections, we present details of over 1500 orbits with eccentricities less than unity. These orbits show (a) a depletion of postperihelion particles with small perihelion distance, suggesting the possibility of collisional and thermal destruction, and (b) an enhancement of particles with perihelia in the zone between Mercury and Venus. Also discussed are 40 β-meteoroids (with radii less than 0.5 μm) dynamically related to the elliptical orbit population with q<0.7 AU. We interpret the latter results on the basis of Poynting–Robertson drag and the electromagnetic resonant effects proposed by G. E. Morfill and E. Grün (1979, Planet. Space Sci. 27, 1269–1282). Comparison with previous data sets indicates that most of the AO micrometeoroid orbits are well randomized and that association with a particular parent body is unlikely.

The capture of interstellar dust: the pure Poynting–Robertson case

Ulysses and Galileo spacecraft have discovered interstellar dust particles entering the solar system. In general, particles trajectories not altered by Lorentz forces or radiation pressure should encounter the sun on open orbits. Under Newtonian forces alone these particles return to the interstellar medium. Dissipative forces, such as Poynting–Robertson (PR) and corpuscular drag and non-dissipative Lorentz forces can modify open orbits to become closed. In particular, it is possible for the orbits of particles that pass close to the sun to become closed due to PR drag. Further, solar irradiation will cause modification of the size of the dust particle by evaporation. The combination of these processes gives rise a class of capture orbits and bound orbits with evaporation. Considering only the case of pure PR drag a minimum impact parameter is derived for initial capture by Poynting–Robertson drag. Orbits in the solar radiation field are computed numerically accounting for evaporation with optical and material properties for ideal interstellar particles modeled. The properties of this kind of particle capture are discussed for the Sun but is applicable to other stars.

Temporal variation of the zodiacal dust cloud

A Markov chain model is constructed to investigate fluctuations in the mass of the zodiacal cloud. The cloud is specified by a three-dimensional grid, each element of which contains the numbers of dust particles as a function of semimajor axis, eccentricity and mass. The evolutionary pathways of dust particles owing to radiation pressure are described by fixed transition probabilities connecting the grid elements. Other elements are absorbing states representing infall to the Sun or ejection to infinity: particles entering these states are removed from the system. Particles are injected through the breakup of comets entering short-period, high-eccentricity orbits at random times, and are subject to the Poynting—Robertson effect and removal through collisional disintegration and radiation pressure. The main conclusions are that the cometary component of the zodiacal cloud is highly variable, and that in the wake of giant comet entry into a short-period, near-Earth orbit, the dust influx to the Earth's atmosphere may acquire a climatically significant optical depth.