Inner core-mantle gravitational locking and the super-rotation of the inner core
Bibliographic record
Abstract
Seismological observations suggest that the Earth's solid inner core has been rotating faster than the mantle over the past several decades, consistent with the results of some numerical geodynamo models. However, the hemispherical anisotropy structure of the inner core, also seismically observed, may require the inner core to remain at a relatively fixed longitudinal alignment with respect to the mantle, perhaps due to gravitational locking between them. Both of these seismic observations may be compatible if the differential rotation of the inner core is oscillatory in nature, with no mean offset over geologically long timescales. In this work, we investigate the possible rates of rotation of an oscillating inner core and the dynamics of coupling within the core–mantle system from an angular momentum perspective. We find that gravitational coupling between the inner core and mantle acts to prevent differential rotation, although the period at which 'locking' occurs differs depending on which of the inner core or mantle is driving the motion. We also show that for an internally generated torque, a long period (longer than 100 yr) oscillation of the inner core with a rate equal to 0.25° yr−1, on the high end of the rates inferred from seismic observations, is possible. However, the mantle oscillations entrained by gravitational coupling in such a scenario are only marginally compatible with the observed changes in length of day. We show that, in order to explain the seismically inferred rotation rates, either the gravitational coupling must be lower than previous estimates, or the electromagnetic coupling at the core–mantle boundary must be stronger than typical estimates.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".