Mineral Processing by Short Circuits in Protoplanetary Disks

Abstract

Meteoritic chondrules were formed in the early solar system by brief heating of silicate dust to melting temperatures. Some highly refractory grains (Type B calcium-aluminum-rich inclusions, CAIs) also show signs of transient heating. A similar process may occur in other protoplanetary disks, as evidenced by observations of spectra characteristic of crystalline silicates. One possible environment for this process is the turbulent magnetohydrodynamic flow thought to drive accretion in these disks. Such flows generally form thin current sheets, which are sites of magnetic reconnection, and dissipate the magnetic fields amplified by a disk dynamo. We suggest that it is possible to heat precursor grains for chondrules and other high-temperature minerals in current sheets that have been concentrated by our recently described short-circuit instability. We extend our work on this process by including the effects of radiative cooling, taking into account the temperature dependence of the opacity; and by examining current sheet geometry in three-dimensional, global models of magnetorotational instability. We find that temperatures above 1600 K can be reached for favorable parameters that match the ideal global models. This mechanism could provide an efficient means of tapping the gravitational potential energy of the protoplanetary disk to heat grains strongly enough to form high-temperature minerals. The volume-filling nature of turbulent magnetic reconnection is compatible with constraints from chondrule-matrix complementarity, chondrule-chondrule complementarity, the occurrence of igneous rims, and compound chondrules. The same short-circuit mechanism may perform other high-temperature mineral processing in protoplanetary disks such as the production of crystalline silicates and CAIs.

6 pages, 3 figures, ApJL published version

References in corpus (14)

• Dust Grain Size Distributions and Extinction in the Milky Way, LMC, and SMC
• Accretion Disks Around Young Objects. III. Grain Growth
• Dynamics of Protoplanetary Disks
• The ionization fraction in alpha-models of protoplanetary disks
• Magnetorotational Instability Driven Accretion in Protoplanetary Disks
• Self-Sustained Ionization and Vanishing Dead Zones in Protoplanetary Disks
• The Role of Tiny Grains on the Accretion Process in Protoplanetary Disks
• Chondrule Formation and Protoplanetary Disk Heating by Current Sheets in Non-Ideal Magnetohydrodynamic Turbulence
• Short Circuits in Thermally Ionized Plasmas: A Mechanism for Intermittent Heating of Protoplanetary Disks
• Radiative transfer in decomposed domains
• Interdependence of Electric Discharge and The Magnetorotational Instability in Protoplanetary Disks
• Phurbas: An Adaptive, Lagrangian, Meshless, Magnetohydrodynamics Code. I. Algorithm
• Phurbas: An Adaptive, Lagrangian, Meshless, Magnetohydrodynamics Code. II. Implementation and Tests
• The Accretion Disc Dynamo in the Solar Nebula

Cited by in corpus (20)

• High-Temperature Ionization in Protoplanetary Disks
• Abundance, Major Element Composition and Size of Components and Matrix in CV, CO and Acfer 094 Chondrites
• The Origin of Chondrules: Constraints from Matrix-Chondrule Complementarity
• Mixing and transport of dust in the early solar nebula as inferred from titanium isotope variations among chondrules
• Trace element geochemistry of ordinary chondrite chondrules: the type I/type II chondrule dichotomy
• The quasi-universality of chondrule size as a constraint for chondrule formation models
• Harvesting the decay energy of ${}^{26}$Al to drive lightning discharge in protoplanetary discs
• Protoplanetary dust porosity and FU Orionis Outbursts: Solving the mystery of Earth's missing volatiles
• Temperature Fluctuations driven by Magnetorotational Instability in Protoplanetary Disks
• The Nonlinear Ohm's Law: Plasma Heating by Strong Electric Fields and its Effects on the Ionization Balance in Protoplanetary Disks
• Planetary Embryo Bow Shocks as a Mechanism for Chondrule Formation
• Explaining Mercury's Density through Magnetic Erosion
• A New Mechanism for Chondrule Formation: Radiative Heating by Hot Planetesimals
• Fast methods to track grain coagulation and ionization. II. Extension to thermal ionization
• Dissipative structures in magnetorotational turbulence
• Semarkona: Lessons for chondrule and chondrite formation
• Ejection of Chondrules from Fluffy Matrices
• The motion of chondrules and other particles in a protoplanetary disc with temperature fluctuations
• Development of a Method for the Observation of Lightning in Protoplanetary Disks Using Ion Lines
• Generating potassium abundance variations in the Solar Nebula