Dust-Dust Collisional Charging and Lightning in Protoplanetary Discs

Authors: Takayuki Muranushi

(Submitted on 11 Aug 2009)

Abstract: We study the role of dust-dust collisional charging in protoplanetary discs. We show that dust-dust collisional charging becomes an important process in determining the charge state of dust and gas, if there is dust enhancement and/or dust is fluffy, so that dust surface area per disc volume is locally increased.

We solve the charge equilibrium equations for various disc environments and dust condensation $\eta$ (dust number density of the considered region divided by the fiducial value), using general purpose graphic processors (GPGPU) and {\sc cuda} programming language. We found that as dust condensation $\eta$ increases, the charge distribution experience four phases.

In one of these phases the electrostatic field $E$ caused by dust migration increases as $E \propto \eta^4$. As a result, macroscopic electric discharge takes place typically at $\eta = 30 \sim 300$. We present a model that describes the charge exchange processes in the discs as an electric circuit.

We estimate the total energy, intensity and event ratio of such discharges (`lightning’). We discuss the possibility of observing lightning and sprite discharges in protoplanetary discs by Astronomically Low Frequency ({\em ALF}) waves, {\em IR} images, {\em UV} lines, and high energy gamma rays. We also discuss the effects of lightning on chondrule heating, planetesimal growth and magnetorotational instability of the disc.

Comments: 23 pages, 34 figures, submitted to MNRAS

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

Cite as: arXiv:0908.1575v1 [astro-ph.EP]

Submission history

From: Takayuki Muranushi [view email]

[v1] Tue, 11 Aug 2009 20:20:22 GMT (4497kb)

http://arxiv.org/abs/0908.1575