P. Pástor

Motion of dust in mean motion resonances with planets

Effect of stellar electromagnetic radiation on the motion of spherical dust particle in mean motion orbital resonances with a planet is investigated. Planar circular restricted three-body problem with the Poynting–Robertson (P–R) effect yields monotonic secular evolution of eccentricity when the particle is trapped in the resonance. Planar elliptic restricted three-body problem with the P–R effect enables nonmonotonous secular evolution of eccentricity and the evolution of eccentricity is qualitatively consistent with the published results for the complicated case of interaction of electromagnetic radiation with nonspherical dust grain. Thus, it is sufficient to allow either nonzero eccentricity of the planet or nonsphericity of the grain and the orbital evolutions in the resonances are qualitatively equal for the two cases. This holds both for exterior and interior mean motion orbital resonances. Evolutions of argument of perihelion in the planar circular and elliptical restricted three-body problems are shown. Numerical integrations show that an analytic expression for the secular time derivative of the particle’s argument of perihelion does not exist, if only dependence on semimajor axis, eccentricity and argument of perihelion is admitted. Connection between the shift of perihelion and oscillations in secular eccentricity is presented for the planar elliptic restricted three-body problem with the P–R effect. Period of the oscillations corresponds to the period of one revolution of perihelion. Change of optical properties of the spherical grain with the heliocentric distance is also considered. The change of the optical properties: (i) does not have any significant influence on the secular evolution of eccentricity, (ii) causes that the shift of perihelion is mainly in the same direction/orientation as the particle motion around the Sun. The statements hold both for circular and noncircular planetary orbits.

The non-radial component of the solar wind and motion of dust near mean motion resonances with planets

We investigate the effect of solar wind and solar electromagnetic radiation on the dynamics of spherical cosmic dust particles. We also consider the non-radial component of the solar wind velocity, in the reference frame of the Sun. We apply the equation of motion to the motion of dust grains near commensurability resonances with a planet – mean motion orbital resonance (MMR; a particle is in resonance with a planet when the ratio of their mean motions is approximately the ratio of two small integers) – and possible capture of the grains in the resonances. Up to now, only nonspherical grains, under action of the electromagnetic radiation of the central star, were known to exhibit an increase of semimajor axis before capture into the MMR. This paper shows that the same result can be generated by the non-radial component of the solar wind even for spherical dust particles. Spherical dust grains enable the treatment of the problem in an analytic way (at least partially), which is not the case for the effect of electromagnetic radiation on nonspherical dust grains. The situation treated in the paper presents the second known case when resonant trapping of a cosmic body occurs for diverging orbits. The paper presents the first case of secular evolution of the eccentricity of a body captured in the resonance derived in an analytic way for a body characterized by a diverging orbit.

Orbital evolution under the action of fast interstellar gas flow

We investigate the orbital evolution of an interplanetary dust particle under the action of an interstellar gas flow. We present the secular time derivatives of the particles orbital elements, for arbitrary orbit orientation. An important result concerns the secular evolution of the semimajor axis. The secular semimajor axis of the particle on a bound orbit decreases under the action of fast interstellar gas flow. In this paper, we discuss the possible types of evolution of other Keplerian orbital elements. Also, we compare the influences of the Poynting–Robertson effect, the radial solar wind and the interstellar gas flow on the dynamics of the dust particle in the outer planetary region of the Solar system and beyond, up to 100 au. We study the evolution of a putative dust ring in the zone of the Edgeworth–Kuiper belt. The non-radial solar wind and the gravitational effect of the major planets might have an important role in this zone. We take into account both these effects. The low-inclination orbits of micrometre-sized dust particles in the belt are not stable, because of the fast increase of eccentricity caused by the long-term monodirectional interstellar gas flow and subsequent planetary perturbations – the increase of eccentricity leads to the planet-crossing orbits of the particles. Gravitational and non-gravitational effects are treated in a way that fully respects physics. As a consequence, some of the published results have turned out to be incorrect. Moreover, in this paper we treat the problem in a more general way than it has been presented up to now. The influence of the fast interstellar neutral gas flow should not be ignored in the modelling of the evolution of dust particles beyond planets.

Eccentricity evolution in mean motion resonance and non-radial solar wind

Eccentricity evolution of a dust particle in a mean motion orbital resonance with a planet in circular orbit is investigated. The action of solar electromagnetic and corpuscular radiation, including non-radial components of the solar wind velocity, is taken into account. Various types of eccentricity evolution depend on the angle between the radial direction and the direction of the solar wind velocity. The evolution changes at the analytically derived angles. Its application to exosolar systems is included.

On the stability of dust orbits in mean-motion resonances perturbed by from an interstellar wind

Circumstellar dust particles can be captured in a mean-motion resonance (MMR) with a planet and simultaneously be affected by non-gravitational effects. It is possible to describe the secular variations of a particle orbit in the MMR analytically using averaged resonant equations. We derive the averaged resonant equations from the equations of motion in near-canonical form. The secular variations of the particle orbit depending on the orientation of the orbit in space are taken into account. The averaged resonant equations can be derived/confirmed also from Lagrange’s planetary equations. We apply the derived theory to the case when the non-gravitational effects are the Poynting–Robertson effect, the radial stellar wind, and an interstellar wind. The analytical and numerical results obtained are in excellent agreement. We found that the types of orbits correspond to libration centers of the conservative problem. The averaged resonant equations can lead to a system of equations which holds for stationary points in a subset of resonant variables. Using this system we show analytically that for the considered non-gravitational effects, all stationary points should correspond to orbits which are stationary in interplanetary space after an averaging over a synodic period. In an exact resonance, the stationary orbits are stable. The stability is achieved by a periodic repetition of the evolution during the synodic period. Numerical solutions of this system show that there are no stationary orbits for either the exact or non-exact resonances.