Magnetic Fields Recorded by Chondrules Formed in Nebular Shocks

Chuhong Mai, Steven Desch, Aaron C. Boley, Benjamin P. Weiss

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Recent laboratory efforts have constrained the remanent magnetizations of chondrules and the magnetic field strengths to which the chondrules were exposed as they cooled below their Curie points. An outstanding question is whether the inferred paleofields represent the background magnetic field of the solar nebula or were unique to the chondrule-forming environment. We investigate the amplification of the magnetic field above background values for two proposed chondrule formation mechanisms, large-scale nebular shocks and planetary bow shocks. Behind large-scale shocks, the magnetic field parallel to the shock front is amplified by factors of ∼10-30, regardless of the magnetic diffusivity. Therefore, chondrules melted in these shocks probably recorded an amplified magnetic field. Behind planetary bow shocks, the field amplification is sensitive to the magnetic diffusivity. We compute the gas properties behind a bow shock around a 3000 km radius planetary embryo, with and without atmospheres, using hydrodynamics models. We calculate the ionization state of the hot, shocked gas, including thermionic emission from dust, thermal ionization of gas-phase potassium atoms, and the magnetic diffusivity due to Ohmic dissipation and ambipolar diffusion. We find that the diffusivity is sufficiently large that magnetic fields have already relaxed to background values in the shock downstream where chondrules acquire magnetizations, and that these locations are sufficiently far from the planetary embryos that chondrules should not have recorded a significant putative dynamo field generated on these bodies. We conclude that, if melted in planetary bow shocks, chondrules probably recorded the background nebular field.

Original languageEnglish (US)
Article number96
JournalAstrophysical Journal
Volume857
Issue number2
DOIs
StatePublished - Apr 20 2018

Fingerprint

chondrule
shock
magnetic field
bows
magnetic fields
diffusivity
embryos
embryo
amplification
ionization
gas
ohmic dissipation
Curie point
magnetization
solar nebula
ambipolar diffusion
thermionic emission
shock fronts
remanent magnetization
high temperature gases

Keywords

  • magnetic fields
  • meteorites, meteors, meteoroids
  • protoplanetary disks
  • shock waves

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Magnetic Fields Recorded by Chondrules Formed in Nebular Shocks. / Mai, Chuhong; Desch, Steven; Boley, Aaron C.; Weiss, Benjamin P.

In: Astrophysical Journal, Vol. 857, No. 2, 96, 20.04.2018.

Research output: Contribution to journalArticle

Mai, Chuhong ; Desch, Steven ; Boley, Aaron C. ; Weiss, Benjamin P. / Magnetic Fields Recorded by Chondrules Formed in Nebular Shocks. In: Astrophysical Journal. 2018 ; Vol. 857, No. 2.
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