Collisional Charging in the Low Pressure Range of Protoplanetary Disks

TL;DR

This study measures how collisional charging varies with pressure in protoplanetary disks, revealing that significant charging occurs across a wide pressure range and may influence planet formation processes.

Contribution

First pressure-dependent charge measurements for same material collisions across a broad pressure range, linking breakdown voltage to grain charging in protoplanetary disks.

Findings

Strong charging occurs down to the lowest pressures studied.

Charging behavior resembles breakdown voltage dependence.

Collisional charging is possible throughout protoplanetary disks.

Abstract

In recent years, collisional charging has been proposed to promote the growth of pebbles in early phases of planet formation. Ambient pressure in protoplanetary disks spans a wide range from below $10^{-9}$ mbar up to way beyond mbar. Yet, experiments on collisional charging of same material surfaces have only been conducted under Earth atmospheric pressure, Martian pressure and more generally down to $10^{-2}$ mbar thus far. This work presents first pressure dependent charge measurements of same material collisions between $10^{-8}$ and $10^3$ mbar. Strong charging occurs down to the lowest pressure. In detail, our observations show a strong similarity to the pressure dependence of the breakdown voltage between two electrodes and we suggest that breakdown also determines the maximum charge on colliding grains in protoplanetary disks. We conclude that collisional charging can occur in all parts of protoplanetary disks relevant for planet formation.