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PreprintCC BY-NC-ND 4.0arXiv

Hydrogen Engulfment into Sub-Neptune Cores through Magma Ocean Convective Surface Renewal

  • Edward D. Young
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Abstract

A convective surface renewal explanation for ingassing of hydrogen from H2-rich envelopes into molten cores of growing planets is presented, with particular application to sub-Neptunes. The ingassing of hydrogen occurs at a moving front comprising the upper boundary of the magma ocean that engulfs hydrogen from the envelope above as it moves. The mechanism of engulfment is surface renewal as the upper diffusive boundary layer is diluted by convection. Surface renewal results in ingassing even where the stabilizing buoyancy of the low-density hydrogen neutralizes the destabilizing thermally-driven buoyancy. It is ultimately driven by cooling. Beginning during the gaseous disk phase, when hydrogen is effectively available in infinite supply, sub-Neptunes can acquire enough hydrogen to permit global core-envelope equilibrium. The structures are therefore consistent with hydrogen-rich, supercritical magma oceans overlain by hydrogen-rich envelopes. The process of surface renewal has implications for other magma ocean - atmosphere interactions in general.

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Cite

BibTeXRIS
BibTeX
@misc{young2026hydrogen,
  title = {{Hydrogen Engulfment into Sub-Neptune Cores through Magma Ocean Convective Surface Renewal}},
  author = {Edward D. Young},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2608.14518},
  eprint = {2608.14518},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2608.14518},
  note = {CC BY-NC-ND 4.0},
}
RIS
TY  - UNPB
TI  - Hydrogen Engulfment into Sub-Neptune Cores through Magma Ocean Convective Surface Renewal
AU  - Edward D. Young
PY  - 2026
DA  - 2026/10/09
PB  - arXiv
DO  - 10.48550/arxiv.2608.14518
UR  - https://arxiv.org/abs/2608.14518
AB  - A convective surface renewal explanation for ingassing of hydrogen from H2-rich envelopes into molten cores of growing planets is presented, with particular application to sub-Neptunes. The ingassing of hydrogen occurs at a moving front comprising the upper boundary of the magma ocean that engulfs hydrogen from the envelope above as it moves. The mechanism of engulfment is surface renewal as the upper diffusive boundary layer is diluted by convection. Surface renewal results in ingassing even where the stabilizing buoyancy of the low-density hydrogen neutralizes the destabilizing thermally-driven buoyancy. It is ultimately driven by cooling. Beginning during the gaseous disk phase, when hydrogen is effectively available in infinite supply, sub-Neptunes can acquire enough hydrogen to permit global core-envelope equilibrium. The structures are therefore consistent with hydrogen-rich, supercritical magma oceans overlain by hydrogen-rich envelopes. The process of surface renewal has implications for other magma ocean - atmosphere interactions in general.
ER  -