Strong Toroidal Recirculation Zones at the Inner Dust Rim as the Origin of Meteoric Chondrules and Calcium-Aluminum Inclusions
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arXiv
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| Format: | Preprint |
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2025
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| _version_ | 1866912349704683520 |
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| author | Williams, Peter Todd |
| author_facet | Williams, Peter Todd |
| contents | We hypothesize strong (transonic) twin toroidal recirculation zones above and below the accretion disk midplane, rather close-in to the protosun, to be the source of chondrules and calcium-aluminum inclusions (CAIs). The recirculation zones act as centrifugal separators. In the case of chondrules, we suggest this happens during Class II (T~Tauri) stage of protostellar accretion, and in the case of CAIs, during an earlier higher-$\dot M$ phase of accretion. The recirculation zones advect and raise dust and solid aggregates above the midplane, making a ``mushroom-cap,'' and they also generate weak standing oblique shocks that heat and fuse protochondrules. We do not model the emission of these shocks, but point out that they will produce Doppler-broadened, possibly twin-peaked line emission with width of the order of $\simeq 200\ {\rm km\ s^{-1}}$. For concreteness, we focus on chondrules in the paper. Small ($\lessapprox 10 {\rm\ μm}$) diameter protochondrules are evaporated by the standing shocks, whereas large ($\gtrapprox 1\ {\rm cm}$) protochondrules are too heavy to be entrained and accelerated by the outer recirculation zone and outflow. Intermediate-size protochondrules, however, are centrifugally ejected and carried by high-speed diffuse gas outflow to the outer regions of the disk, where they rain down. The recirculation-induced dust mushroom caps will create significant IR continuum emission. We suggest they coincide with observed inner ``puffed-up'' dust rims. We also suggest that the recent interferometric inferences of arcs or ellipses in the sub-AU continuum IR of low-mass Class II protostars may be observations of corresponding chondrule-producing recirculation zones in those systems. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2504_19435 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Strong Toroidal Recirculation Zones at the Inner Dust Rim as the Origin of Meteoric Chondrules and Calcium-Aluminum Inclusions Williams, Peter Todd Earth and Planetary Astrophysics We hypothesize strong (transonic) twin toroidal recirculation zones above and below the accretion disk midplane, rather close-in to the protosun, to be the source of chondrules and calcium-aluminum inclusions (CAIs). The recirculation zones act as centrifugal separators. In the case of chondrules, we suggest this happens during Class II (T~Tauri) stage of protostellar accretion, and in the case of CAIs, during an earlier higher-$\dot M$ phase of accretion. The recirculation zones advect and raise dust and solid aggregates above the midplane, making a ``mushroom-cap,'' and they also generate weak standing oblique shocks that heat and fuse protochondrules. We do not model the emission of these shocks, but point out that they will produce Doppler-broadened, possibly twin-peaked line emission with width of the order of $\simeq 200\ {\rm km\ s^{-1}}$. For concreteness, we focus on chondrules in the paper. Small ($\lessapprox 10 {\rm\ μm}$) diameter protochondrules are evaporated by the standing shocks, whereas large ($\gtrapprox 1\ {\rm cm}$) protochondrules are too heavy to be entrained and accelerated by the outer recirculation zone and outflow. Intermediate-size protochondrules, however, are centrifugally ejected and carried by high-speed diffuse gas outflow to the outer regions of the disk, where they rain down. The recirculation-induced dust mushroom caps will create significant IR continuum emission. We suggest they coincide with observed inner ``puffed-up'' dust rims. We also suggest that the recent interferometric inferences of arcs or ellipses in the sub-AU continuum IR of low-mass Class II protostars may be observations of corresponding chondrule-producing recirculation zones in those systems. |
| title | Strong Toroidal Recirculation Zones at the Inner Dust Rim as the Origin of Meteoric Chondrules and Calcium-Aluminum Inclusions |
| topic | Earth and Planetary Astrophysics |
| url | https://arxiv.org/abs/2504.19435 |