# Photophoresis in the circumjovian disk and its impact on the orbital configuration of the Galilean satellites

## TL;DR

This paper proposes that photophoresis in the circumjovian disk creates a surface density bump near Io's orbit, explaining the orbital resonances of the Galilean satellites through halted inward migration.

## Contribution

It introduces a novel mechanism where photophoresis causes a surface density bump, influencing satellite orbital configurations in the circumjovian disk.

## Key findings

- Photophoresis can create a surface density bump near Io's orbit.
- The bump halts inward dust migration, affecting satellite formation.
- Increased ionization and accretion stress occur at the bump.

## Abstract

Jupiter has four large regular satellites called the Galilean satellites: Io, Europa, Ganymede, and Callisto. The inner three of the Galilean satellites orbit in a 4:2:1 mean motion resonance; therefore their orbital configuration may originate from the stopping of the migration of Io near the bump in the surface density distribution and following resonant trapping of Europa and Ganymede. The formation mechanism of the bump near the orbit of the innermost satellite, Io, is not yet understood, however. Here, we show that photophoresis in the circumjovian disk could be the cause of the bump, using analytic calculations of steady-state accretion disks. We propose that photophoresis in the circumjovian disk could stop the inward migration of dust particles near the orbit of Io. The resulting dust depleted inner region would have a higher ionization fraction, and thus admit increased magnetorotational-instability-driven accretion stress than the outer region. The increase of the accretion stress at the photophoretic dust barrier would form a bump in the surface density distribution, halting the migration of Io.