ELECTRIC CHARGING OF DUST AGGREGATES AND ITS EFFECT ON DUST COAGULATION IN PROTOPLANETARY DISKS

By S. Okuzumi. 2009

156 citations recorded by the source corpus.

Mutual sticking of dust aggregates is the first step toward planetesimal formation in protoplanetary disks. In spite that the electric charging of dust particles is well recognized in some contexts, it has been largely ignored in the current modeling of dust coagulation. In this study, we present a general analysis of the dust charge state in protoplanetary disks, and then demonstrate how the electric charging could dramatically change the currently accepted scenario of dust coagulation. First, we describe a new semianalytical method to calculate the dust charge state and gas ionization state self-consistently. This method is far more efficient than previous numerical methods, and provides a general and clear description of the charge state of a gas–dust mixture. Second, we apply this analysis to compute the collisional cross section of growing aggregates taking their charging into account. As an illustrative example, we focus on early evolutionary stages where the dust has been thought to grow into fractal (D ∼ 2) aggregates with a quasi-monodisperse (i.e., narrow) size distribution. We find that, for a wide range of model parameters, the fractal growth is strongly inhibited by the electric repulsion between colliding aggregates and eventually “freezes out” on its way to the subsequent growth stage involving collisional compression. Strong disk turbulence would help the aggregates to overcome this growth barrier, but then it would cause catastrophic collisional fragmentation in later growth stages. These facts suggest that the combination of electric repulsion and collisional fragmentation would impose a serious limitation on dust growth in protoplanetary disks. We propose a possible scenario of dust evolution after the freezeout. Finally, we point out that the fractal growth of dust aggregates tends to maintain a low ionization degree and, as a result, a large magnetorotationally stable region in the disk.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/f02f3823367df1898d6915d37c5c097121ce66c0

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In Astronomy and Astrophysics

1. T. Birnstiel
2. Xue-Ning Bai
3. Anders Johansen
4. C. Dullemond
5. Th. Henning
6. L. Ricci
7. Simon Bruderer
8. H. Klahr

Citations in the corpus

• Trapping dust particles in the outer regions of protoplanetary disks (2011, background): “…aimed to explain theoretically the growth from small dust particles to planetesimals, which have led to the development of different numerical models, e.g. Nakagawa et al. (1981), Dullemond & Dominik (2005), Brauer et al. (2008), Zsom & Dullemond (2008), Okuzumi (2009), Birnstiel et al. (2010a).”
• RADIATION MAGNETOHYDRODYNAMIC SIMULATIONS OF PROTOSTELLAR COLLAPSE: NONIDEAL MAGNETOHYDRODYNAMIC EFFECTS AND EARLY FORMATION OF CIRCUMSTELLAR DISKS (2015, methodology): “The ohmic resistivity and ambipolar diffusion rate are calculated based on the method described in Nakano et al. (2002) and Okuzumi (2009).”
• A simple model for the evolution of the dust population in protoplanetary disks (2012, background): “However there are several mechanisms that can limit collisional growth of dust particles: charging effects (Okuzumi 2009), bouncing (Güttler et al. 2010; Zsom et al. 2010), fragmentation and radial drift (Weidenschilling 1977a; Brauer et al. 2008a; Birnstiel et al. 2010).”
• GLOBAL SIMULATIONS OF PROTOPLANETARY DISKS WITH OHMIC RESISTIVITY AND AMBIPOLAR DIFFUSION (2015, background): “The grains are less important for the ionization state in the FUV layer, where the electrons are so abundant that many remain free once the grains charge to the Coulomb limit (Okuzumi 2009).”
• Gaps, Rings, and Non-Axisymmetric Structures in Protoplanetary Disks - From Simulations to ALMA Observations (2014, background): “The abundances of the main ion, electrons, and charged dust were obtained assuming that the chemistry quickly reaches the charge equilibrium in the presence of small fractal dust (Okuzumi 2009).”
• RAPID COAGULATION OF POROUS DUST AGGREGATES OUTSIDE THE SNOW LINE: A PATHWAY TO SUCCESSFUL ICY PLANETESIMAL FORMATION (2012, background): “In order to clarify the role of porosity evolution, we ignore many other effects relevant to aggregate collision, including Coulomb interaction (Okuzumi 2009; Okuzumi et al. 2011a,b; Matthews et al. 2012), bouncing (Zsom et al. 2010, 2011; Windmark et al. 2012), and collisional fragmentation…”
• RADIATION MAGNETOHYDRODYNAMIC SIMULATIONS OF PROTOSTELLAR COLLAPSE: PROTOSTELLAR CORE FORMATION (2012, methodology): “For non-thermal processes, we adopt the table of resistivity based on the reaction network model between dust grains and chemical species constructed by Umebayashi & Nakano (2009; see also Okuzumi 2009).”