Magnetic Fields Recorded by Chondrules Formed in Nebular Shocks
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 t...
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| Format: | Article |
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American Astronomical Society/IOP Publishing
2018
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| Online Access: | http://hdl.handle.net/1721.1/118354 https://orcid.org/0000-0003-3113-3415 |
| _version_ | 1826202906797277184 |
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| author | Mai, Chuhong Desch, Steven J. Boley, Aaron C. Weiss, Benjamin P. |
| author2 | Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences |
| author_facet | Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences Mai, Chuhong Desch, Steven J. Boley, Aaron C. Weiss, Benjamin P. |
| author_sort | Mai, Chuhong |
| collection | MIT |
| description | 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. Key words: magnetic fields, meteorites, meteors, meteoroids, protoplanetary disks, shock waves |
| first_indexed | 2024-09-23T12:25:47Z |
| format | Article |
| id | mit-1721.1/118354 |
| institution | Massachusetts Institute of Technology |
| last_indexed | 2024-09-23T12:25:47Z |
| publishDate | 2018 |
| publisher | American Astronomical Society/IOP Publishing |
| record_format | dspace |
| spelling | mit-1721.1/1183542024-05-15T04:35:04Z Magnetic Fields Recorded by Chondrules Formed in Nebular Shocks Mai, Chuhong Desch, Steven J. Boley, Aaron C. Weiss, Benjamin P. Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences Weiss, Benjamin P 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. Key words: magnetic fields, meteorites, meteors, meteoroids, protoplanetary disks, shock waves United States. National Aeronautics and Space Administration (NNX15AH72G) 2018-10-04T15:26:06Z 2018-10-04T15:26:06Z 2018-03 2018-03 2018-10-04T14:09:30Z Article http://purl.org/eprint/type/JournalArticle 1538-4357 http://hdl.handle.net/1721.1/118354 Mai, Chuhong, et al. “Magnetic Fields Recorded by Chondrules Formed in Nebular Shocks.” The Astrophysical Journal, vol. 857, no. 2, Apr. 2018, p. 96. © 2018. The American Astronomical Society. https://orcid.org/0000-0003-3113-3415 http://dx.doi.org/10.3847/1538-4357/aab711 The Astrophysical Journal Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf American Astronomical Society/IOP Publishing IOP Publishing |
| spellingShingle | Mai, Chuhong Desch, Steven J. Boley, Aaron C. Weiss, Benjamin P. Magnetic Fields Recorded by Chondrules Formed in Nebular Shocks |
| title | Magnetic Fields Recorded by Chondrules Formed in Nebular Shocks |
| title_full | Magnetic Fields Recorded by Chondrules Formed in Nebular Shocks |
| title_fullStr | Magnetic Fields Recorded by Chondrules Formed in Nebular Shocks |
| title_full_unstemmed | Magnetic Fields Recorded by Chondrules Formed in Nebular Shocks |
| title_short | Magnetic Fields Recorded by Chondrules Formed in Nebular Shocks |
| title_sort | magnetic fields recorded by chondrules formed in nebular shocks |
| url | http://hdl.handle.net/1721.1/118354 https://orcid.org/0000-0003-3113-3415 |
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