Dynamics of charged dust particles in protoplanetary discs

TL;DR

This paper analytically investigates how magnetic fields influence the motion of charged dust particles in protoplanetary discs, revealing that only micron-sized grains are significantly affected, with charge polarity impacting their velocity directions.

Contribution

It provides an analytical model for dust particle velocities in magnetized protoplanetary discs, highlighting the size-dependent magnetic effects and the role of charge polarity.

Findings

Micron-sized grains are affected by magnetic forces.

Larger grains' motion is independent of magnetic fields.

Charge polarity influences the direction of radial velocity.

Abstract

We study the effect of an imposed magnetic field on the motion of charged dust particles in magnetically active regions of a protoplanetary disc. Assuming a power law structure for the vertical and the toroidal components of the magnetic field for the regions beyond magnetically dead region of the disc, the radial and the vertical velocities of the charged particles, in the asymptotic case of small particles, are calculated analytically. While grains with radii smaller than a critical radius significantly are affected by the magnetic force, motion of the particles with larger radii is independent of the magnetic field. The critical radius depends on the magnetic geometry and the charge of the grains. Assuming that a grain particle has one elementary charge and the physical properties of the disc correspond to a minimum-mass solar nebula, we show that only micron-sized grains are affected by the magnetic force. Also, charge polarity determines direction of the radial velocity. For such small particles, both the radial and the vertical velocities increase due to the magnetic force.