Implications for Chondrule Formation Regions and Solar Nebula Magnetism from Statistical Reanalysis of Chondrule Paleomagnetism

Abstract

Converging lines of evidence show that protoplanetary disks are complex environments hosting spatial and temporal variability at multiple scales. Here we reanalyze paleomagnetic estimates of solar nebula magnetic field strengths using a Bayesian framework that tests for recording bias due to chondrule motion and explicitly accounts for time-varying ambient fields. We find that LL and CO group chondrule paleointensities likely rotated during cooling ( p = 0.79–0.99), validating assumptions in previous paleomagnetic studies. Chondrule rotation also suggests low gas density formation environments beyond 2 and 4 au for LL and CO chondrules, respectively. Our recomputed paleointensities for LL and CO chondrules imply either: (1) temporally constant magnetic fields of ${34}_{-14}^{+36}$ μ T and ${106}_{-18}^{+88}$ μ T, respectively; or (2) time-varying magnetic fields with peak amplitudes between ${49}_{-21}^{+97}$ μ T and ${128}_{-11}^{+307}$ μ T. Considering the known mechanisms for sustaining magnetic field gradients and high-amplitude temporal magnetic fluctuations in the solar nebula, we find that magnetic field flux concentrations in disk gaps or time-varying magnetic fields, for example due to the Hall shear instability, are most compatible with the existing data. Using this statistical framework, future paleointensity studies of chondrules can be used to directly test for the variability of magnetic fields in the solar system protoplanetary disk and to distinguish between these scenarios.

Keywords

• Protoplanetary disks
• Planetary system formation
• Asteroid dynamics
• Chondrites
• Chondrules
• Magnetic fields