Interannual oscillations in length of day: Implications for the structure of the mantle and core
Bibliographic record
Abstract
An ∼6‐year variation in the length of day has been observed for which there is no corresponding signal in records of atmospheric angular momentum. We find that this signal can be explained by an exchange of angular momentum with the core arising from gravitational coupling between the mantle and inner core. We develop a theoretical model of the core‐mantle system that includes a combination of gravitational and electromagnetic couplings that allow angular momentum to be transferred between the solid inner core, fluid outer core, and mantle of the Earth. This model is used to calculate the natural period of interannual oscillations in the axial rotation of the core and mantle. The period and quality of the free oscillations depend on physical properties of the core and mantle. Time‐varying geodynamo processes produce torques on the inner core which are capable of exciting the predicted free oscillations to observable levels. The observed length‐of‐day variation is used to constrain the strength of gravitational coupling between the mantle and inner core and hence the degree 2, order 2 component of equipotential surfaces at the inner core boundary and core mantle boundary. This constraint has implications for models of mantle flow.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| 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 | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".