Dust cloud lightning in extraterrestrial atmospheres

TL;DR

This paper explores the potential for lightning and thunderstorms in the mineral clouds of brown dwarfs and extrasolar giant planets, analyzing ionization sources and cloud properties.

Contribution

It introduces the idea that local discharge events are likely in extraterrestrial clouds, extending lightning concepts beyond solar system planets.

Findings

Clouds in brown dwarfs and exoplanets can host lightning-like discharges.

Ionization sources such as thermal processes and cosmic rays may trigger thunderstorms.

Upper cloud layers are most susceptible to powerful discharge events.

Abstract

Lightning is present in all solar system planets which form clouds in their atmospheres. Cloud formation outside our solar system is possible in objects with much higher temperatures than on Earth or on Jupiter: Brown dwarfs and giant extrasolar gas planets form clouds made of mixed materials and a large spectrum of grain sizes. These clouds are globally neutral obeying dust-gas charge equilibrium which is, on short timescales, inconsistent with the observation of stochastic ionization events of the solar system planets. We argue that a significant volume of the clouds in brown dwarfs and extrasolar planets is susceptible to local discharge events and that the upper cloud layers are most suitable for powerful lightning-like discharge events. We discuss various sources of atmospheric ionisation, including thermal ionisation and a first estimate of ionisation by cosmic rays, and argue that we should expect thunderstorms also in the atmospheres of brown dwarfs and giant gas planets which contain mineral clouds.