Observation of bottom-up formation for charged grain aggregates related to pre-planetary evolution beyond the bouncing barrier

Abstract

Context. Particles in protoplanetary disks go through a number of phases that are dominated by collisions. In each of these events, grains exchange electrical charge via triboelectric effects. This enhances the stability of particle aggregates. Aim. Dielectric grains are easily charged by collisions. Here, we investigate whether a charge is capable of inducing an aggregation of particles and we consider how collision properties, such as ticking velocities and collisional cross-sections, are altered. Methods. We explored aggregation in microgravity experiments based on the observation of the motion of submillimeter (submm) grains following many collisions. In the process, grains attract each other, collide, stick, and ultimately form small aggregates. Results. We observed a bottom-up formation of irregular aggregates from submm grains. While some of the observed trajectories during the approach of grains reflect the presence of a pure Coulomb potential, the motion is not always in agreement with pure Kepler motion. Higher-order potentials of multipole charge distributions stand as a plausible explanation for this behavior. An immediate consequence of charging is that the particles continue to stick to each other at velocities of $\sim 10cm/s,$ while surface forces of neutral grains are only expected to allow sticking below $\sim 1mm/s$. No bouncing collision was observed among hundreds of collisions in the given parameter range. Applied to early phases of planet formation, the forming aggregates are therefore the first steps in a new growth phase beyond the traditional bouncing barrier in planet formation.

References in corpus (7)

• Failed Growth at the Bouncing Barrier in Planetesimal Formation
• Ionization and Dust Charging in Protoplanetary Disks
• Is There a Temperature Limit in Planet Formation at 1000 K?
• Quantitatively consistent, scale-spanning model for same-material tribocharging
• Harvesting the decay energy of ${}^{26}$Al to drive lightning discharge in protoplanetary discs
• A Smoking Gun for Planetesimal Formation: Charge Driven Growth into a New Size Range
• Drifting inwards in protoplanetary discs I Sticking of chondritic dust at increasing temperatures

Cited by in corpus (11)

• Aggregation of Sub-mm Particles in Strong Electric Fields under Microgravity Conditions
• The growth of super-large pre-planetary pebbles to an impact erosion limit
• Violation of triboelectric charge conservation on colliding particles
• Electrostatic Repulsion of Dust from Planetary Surfaces
• Positive Feedback: How a Synergy Between the Streaming Instability and Dust Coagulation Forms Planetesimals
• Forbidden planetesimals
• Ionizing Protoplanetary Disks in Pebble Collisions
• Clusters of tribocharged dust aggregates as pebbles in protoplanetary disks
• The Dissolution of Planetesimals in Electrostatic Fields
• Collisional Charging in the Low Pressure Range of Protoplanetary Disks
• Positive Feedback II: How Dust Coagulation inside Vortices Can Form Planetesimals at Low Metallicity