Solar nebula magnetic fields recorded in the Semarkona meteorite

Abstract

24 25 26Accepted Manuscript. This version has not undergone final editing. Please refer to the complete version of record at http://www.sciencemag.org/.2 Magnetic fields are proposed to have played a critical role in some of the most enigmatic 26 processes of planetary formation by mediating the rapid accretion of disk material onto the 27 central star and the formation of the first solids. However, there have been no direct 28 experimental constraints on these fields. Here we show that dusty olivine-bearing 29 chondrules from the Semarkona meteorite were magnetized in a nebular field of 54±21 µT. 30This intensity supports chondrule formation by nebular shocks or planetesimal collisions 31 rather than by electric currents, the x-wind, or other mechanisms near the sun. This 32 implies that background magnetic fields in the terrestrial planet-forming region were likely 33 5-54 µT, which is sufficient to account for measured rates of mass and angular momentum 34 transport in protoplanetary disks. 35 36Astronomical observations of young stellar objects indicate that early planetary systems 37 evolve through a protoplanetary disk phase in <5 million years (My) following the collapse of 38 their parent molecular clouds (1, 2). Disk evolution on such short timescales requires highly 39 efficient inward transport of mass accompanied by outward angular momentum transfer, which 40 allows disk material to accrete onto the central star while delivering angular momentum out of 41 the protoplanetary system. 42The mechanism of this rapid mass and angular momentum redistribution remains unknown. 43Several proposed processes invoke a central role for nebular magnetic fields. Among these, the 44 magnetorotational instability (MRI) and magnetic braking predict magnetic fields with intensities 45 of ~100 µT at 1 AU in the active layers of the disk (3, 4). Alternatively, transport by 46 magnetocentrifugal wind (MCW) requires large-scale, ordered magnetic fields stronger than ~10 47 µT at 1 AU. Finally, non-magnetic effects such as the baroclinic and Goldreich-Schubert-Fricke 48 instabilities may be the dominant mechanism of angular momentum transport in the absence of 49 sufficiently strong magnetic fields (5). Direct measurement of magnetic fields in the planet-50 forming regions of the disk can potentially distinguish among and constrain these hypothesized 51 mechanisms. 52Although current astronomical observations cannot directly measure magnetic fields in 53 planet-forming regions [(6); supplementary text], paleomagnetic experiments on meteoritic 54 materials can potentially constrain the strength of nebular magnetic fields. Chondrules are 55 millimeter-sized lithic constituents of primitive meteorites that formed in transient heating events 56 in the solar nebula. If a stable field was present during cooling, they should have acquired a 57 thermoremanent magnetization (TRM), which can be characterized via paleomagnetic 58 experiments. Besides assessing the role of magnetic fields in disk evolution, such paleomagnetic 59 measure...

On the Grain-Modified Magnetic Diffusivities in Protoplanetary Disks

“…For reference, we also mark the possible field strength of the solar nebula inferred from the Semarkona meteorites (Fu et al 2014), which likely corresponds to a midplane field strength at 2-3 au during the epoch of chondrule formation. Although large uncertainties remain, a field strength of up to 100 b = in an MMSN disk is reasonably consistent with the inferred nebular field strength.…”

Broadband, large-area microwave antenna for optically detected magnetic resonance of nitrogen-vacancy centers in diamond

“…10-13 Consequently, NVbased sensing and imaging of magnetic fields, as well as other physical quantities such as temperatures and electric fields, have become an active area of research and are expected to find practical applications not only in physics but also in biology, medical science, planetary science, and so forth. [14][15][16][17][18][19][20][21] In optically-detected magnetic resonance (ODMR) experiments of NV centers, a thin straight copper wire or a millimeter-sized loop coil is commonly used to generate an oscillating magnetic field B ac . 22,23 For sensing with ensemble NVs, in which the sensitivity is enhanced by the square-root of the number of spins at the expense of nanoscale resolution, the uniformity of B ac is particularly important.…”

Selective addressing of solid-state spins at the nanoscale via magnetic resonance frequency encoding

“…1 For example, single NV centres have been used for a loophole-free Bell test of quantum realism, 2 probing nanoscale phenomena in condensed matter systems, [3][4][5][6][7] and nuclear magnetic resonance (NMR) spectroscopy and imaging of nanoscale ensembles of nuclear spins [8][9][10] including single proteins 11 and individual proton spins. 12 Large ensembles of NV centres have provided magnetic imaging with combined micronscale resolution and millimetre field-of-view, e.g., for mapping paleomagnetism in primitive meteorites 13 and ancient Earth rocks, 14 genetic studies of magnetotactic bacteria, 15,16 and identifying biomarkers in tumour cells. 17 However, it remains a challenge to realize the intermediate regime of mesoscopic arrays of NV spins with selective nanoscale addressing and coherent control of NVs at each site in the array.…”