Magnetic Fields Recorded by Chondrules Formed in Nebular Shocks

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

    Research output: Contribution to journalArticle

    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.
    @article{504e6da090434d61a433cb258f6c0c50,
    title = "Magnetic Fields Recorded by Chondrules Formed in Nebular Shocks",
    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.",
    keywords = "magnetic fields, meteorites, meteors, meteoroids, protoplanetary disks, shock waves",
    author = "Chuhong Mai and Steven Desch and Boley, {Aaron C.} and Weiss, {Benjamin P.}",
    year = "2018",
    month = "4",
    day = "20",
    doi = "10.3847/1538-4357/aab711",
    language = "English (US)",
    volume = "857",
    journal = "Astrophysical Journal",
    issn = "0004-637X",
    publisher = "IOP Publishing Ltd.",
    number = "2",

    }

    TY - JOUR

    T1 - Magnetic Fields Recorded by Chondrules Formed in Nebular Shocks

    AU - Mai, Chuhong

    AU - Desch, Steven

    AU - Boley, Aaron C.

    AU - Weiss, Benjamin P.

    PY - 2018/4/20

    Y1 - 2018/4/20

    N2 - 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.

    AB - 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.

    KW - magnetic fields

    KW - meteorites, meteors, meteoroids

    KW - protoplanetary disks

    KW - shock waves

    UR - http://www.scopus.com/inward/record.url?scp=85046358821&partnerID=8YFLogxK

    UR - http://www.scopus.com/inward/citedby.url?scp=85046358821&partnerID=8YFLogxK

    U2 - 10.3847/1538-4357/aab711

    DO - 10.3847/1538-4357/aab711

    M3 - Article

    VL - 857

    JO - Astrophysical Journal

    JF - Astrophysical Journal

    SN - 0004-637X

    IS - 2

    M1 - 96

    ER -