Parametric coupling of waves is one of the most efficient mechanisms of energy transfer that can lead to the growth or decay of waves. This transfer occurs at frequencies close to their natural ...frequencies. In partially ionized solar plasma, there are a multitude of waves that can undergo this process. Here, we study the parametric coupling of Alfvén waves propagating in a partially ionized solar plasma with ionization-recombination waves identified by our study to appear in a plasma in ionization non-equilibrium. Depending on the parameters that describe the plasma (density, temperature), coupling can lead to a parametric resonance. Our study determines the occurrence conditions of parametric resonance, by finding the boundaries between stable and unstable regions in the parameter space. Our results show that collisions and non-equilibrium recombination can both contribute to the onset of unstable behaviour of parametrically resonant Alfvén waves. This article is part of the theme issue 'Partially ionized plasma of the solar atmosphere: recent advances and future pathways'.
ABSTRACT
This work presents novel findings that broaden our understanding of the amount of water that can be transported to the Earth. The key innovation lies in the combined usage of smoothed ...particle hydrodynamics (SPH) and N-body codes to assess the role of collision fragments in water delivery. We also present a method for generating initial conditions that enables the projectile to impact at the designated location on the target’s surface with the specified velocity. The primary objective of this study is to simulate giant collisions between two Ceres-sized bodies by SPH near the ν6 secular resonance and follow the evolution of the ejected debris by numerical N-body code. With our method 6 different initial conditions for the collision were determined, and the corresponding impacts were simulated by SPH. Examining the orbital evolution of the debris ejected after collisions, we measured the amount of water delivered to the Earth, which is broadly 0.001 ocean equivalents of water, except in one case where one large body transported 7 per cent oceans of water to the planet. Based on this and taking into account the frequency of collisions, the amount of delivered water varies between 1.2 and 8.3 ocean’s worth of water, depending on the primordial disc mass. According to our results, the prevailing external pollution model effectively accounts for the assumed water content on the Earth, whether it’s estimated at 1 or 10 ocean’s worth of water.
Abstract
In this paper, we present a large-scale dynamical survey of the trans-Neptunian region, with particular attention to mean-motion resonances (MMRs). We study a set of 4121 trans-Neptunian ...objects (TNOs), a sample far larger than in previous works. We perform direct long-term numerical integrations that enable us to examine the overall dynamics of the individual TNOs as well as to identify all MMRs. For the latter purpose, we apply an own-developed FAIR method that allows the semi-automatic identification of even very high-order MMRs. Apart from searching for the more frequent eccentricity-type resonances that previous studies concentrated on, we set our method to allow the identification of inclination-type MMRs, too. Furthermore, we distinguish between TNOs that are locked in a given MMR throughout the whole integration time span (10
8
yr) and those that are only temporarily captured in resonances. For a more detailed dynamical analysis of the trans-Neptunian space, we also construct dynamical maps using test particles. Observing the fine structure of the 34–80 au region underlines the stabilizing role of the MMRs, with the regular regions coinciding with the positions of real TNOs.
ABSTRACT
We report an eclipse timing variations (ETV) study to identify close, stellar mass companions to the eclipsing binaries monitored during the photometric survey Optical Gravitational Lensing ...Experiment-IV. We also present an alternative automatic way to determine the first and last contacts of an eclipse. Applying the phase dispersion minimization method to identify potential triples, we find close third components with outer periods in less than 1500 d in 23 systems. We present outer orbit solution for 21 of 23 systems. For the 10 tightest triples, we find that the ETV can only be modelled with the combination of the light-travel-time effect (LTTE) and third-body perturbations, while in case of another 11 systems, pure LTTE solutions are found to be satisfactory. In the remaining two systems, we identify extra eclipses connected to the outer component, but for the incomplete and noisy ETV curves, we are unable to find realistic three-body solutions. Therefore, in these cases we give only the outer period.
ABSTRACT
On long enough time-scales, chaotic diffusion has the potential to significantly alter the appearance of a dynamical system. The Solar system is no exception: diffusive processes take part ...in the transportation of small bodies and provide dynamical pathways even for the distant trans-Neptunian objects to reach the inner Solar system. In this letter, we carry out a thorough investigation of the nature of chaotic diffusion. We analyse the temporal evolution of the mean squared displacement of 10 000 ensembles of test particles and quantify in each case the diffusion exponent (enabling the classification between normal, sub-, and superdiffusion), the generalized diffusion coefficient, and a characteristic diffusion time-scale, too. This latter quantity is compared with an entropy-based time-scale, and the two approaches are studied in light of direct computations as well. Our results are given in the context of two-dimensional maps, thereby facilitating the understanding of the relationship between the typical phase space structures and the properties of chaotic diffusion.
Abstract
The identification of mean motion resonances in exoplanetary systems or in the Solar system might be cumbersome when several planets and large number of smaller bodies are to be considered. ...Based on the geometrical meaning of the resonance variable, an efficient method is introduced and described here, by which mean motion resonances can be easily find without any a priori knowledge on them. The efficiency of this method is clearly demonstrated by using known exoplanets engaged in mean motion resonances, and also some members of different families of asteroids and Kuiper belt objects being in mean motion resonances with Jupiter and Neptune, respectively.
Abstract
We report a study of the eclipse timing variation (ETV) of short period (P1 ≤ 6d) eclipsing binaries (EBs) monitored during the photometric survey optical gravitational lensing ...experiment-IV. From the 425 193 EBs, we selected approximately 80 000 binaries that we found suitable for further examination. Among them, we identified 992 potential hierarchical triple (or multiple) system candidates exhibiting light-travel time effect (LTTE). Besides, we obtained the orbital parameters of these systems and carried out statistical analyses on the properties of these candidates. We found that (i) there is a significant lack of triple systems where the outer period is less than 500 d, (ii) the distribution of the outer eccentricities has a maximum around e2 ≈ 0.3, and (iii) the outer mass ratio calculated from an estimated minimum mass of the third component is lower than q2 ∼ 0.5 for the majority of the sample. We also present some systems that deserve special attention: (i) There are four candidates that show double periodic ETV, which we explain by the presence of a fourth companion; (ii) For two systems, the perturbations of the third component are also found to be significant therefore we give a combined dynamical and LTTE ETV solution; and (iii) For one system, the third component is found to be probably in the substellar mass domain.
Context.
A region at the inner edge of the main asteroid belt is populated by the Hungaria asteroids. Among these objects, the Hungaria family formed as the result of a catastrophic disruption of the ...(434) Hungaria asteroid a few hundred million years ago. Due to the Yarkovsky effect, the fragments depending on their direction of rotation are slowly drifting inwards or outwards from the actual place of collision. Due to this slow drift, these bodies could approach the locations of the various outer-type mean-motion resonances (MMRs) with Mars.
Aims.
We aim to study the actual dynamical structure of Hungaria asteroids, which is primarily shaped by various outer-type MMRs with Mars. Moreover, we also seek connections between the orbital characteristics of Hungaria asteroids and their absolute magnitude.
Methods.
To map the resonant structure and dynamics of asteroids belonging to the Hungaria group, we used the FAst Identification of mean motion Resonances method, which can detect MMRs without the a priori knowledge of the critical argument. We also compiled stability maps of the regions around the MMRs by using the maximal variations in the asteroids’ eccentricities, semi-major axes, and inclinations. We numerically integrated the orbits of all asteroids belonging to the Hungaria group available in the JPL Horizon database together with the Solar System planets for one and ten million years.
Results.
Having studied the resonant structure of the Hungaria group, we find that several asteroids are involved in various MMRs with Mars. We identify both short- and long-term MMRs. Besides this, we also find a relationship between the absolute magnitude of asteroids and the MMR in which they are involved.
From our sample of spotted late‐type stars showing surface differential rotation, we find that the relationship between the rotation period and the surface shear coefficient α = ΔΩ/Ωeq is ...significantly different for single stars compared to members in close binaries. Single stars follow a general trend that α increases with the rotation period. However, differential rotation of stars in close binary systems shows much weaker dependence on the rotation, if any, suggesting that in such systems, tidal forces operate as a controlling mechanism of differential rotation.
Compressional waves propagating in the partially ionised solar lower atmospheric plasmas can easily steepen into nonlinear waves, including shocks. Here we investigate the effect of weak dispersion ...generated by Hall currents perpendicular to the ambient magnetic field on the characteristics of shock waves. Our study will also focus on the interplay between weak dispersion and partial ionisation of the plasma. Using a multiple scale technique we derive the governing equation in the form of a Korteweg-de Vries-Burgers equation. The effect of weak dispersion on shock waves is obtained using a perturbation technique. The secular behaviour of second order terms is addressed with the help of a renormalization technique. Our results show that dispersion modifies the characteristics of shock waves and this change is dependent also on the ionisation degree of the plasma. Dispersion can create short lived oscillations in the shocked plasma. The shock fronts become wider with the increase in the number of neutrals in the plasma.
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