The differential precession of Earth’s fluid and solid cores
Bibliographic record
Abstract
<!--!introduction!--> The Earth's spin axis is inclined by 23.4 degrees with respect to the ecliptic normal and precesses in space with a period of 26 kyr. The fluid core and solid inner core precess at slightly different angles. We compute their differential precession angles on the basis of an elastically deforming Earth and dissipative torques inferred from nutation observations. We show that the precession angle of the fluid core is larger than that of the mantle by 1.714 arcsec and lags behind it by 0.0124 arcsec. The precession angle of the spin (and figure) axis of the inner core is smaller than that of the mantle by 1.861 arcsec and trails behind it by 3.660 arcsec. These correspond to differential velocities ( Δv) at the core mantle boundary (CMB) and inner core boundary (ICB) of 2.11 and 2.21 mm/s, to associated boundary layer Reynolds (Re) numbers of 247 and 258, and to dissipation (D) equal to 4.6 and 14.5 GW. Re at the CMB has remained approximately constant in the past 4 Gyr. At the ICB, Δv, Re and D have all increased since inner core formation. Our results suggest that, for the whole of Earth's history, dissipation from the misaligned precession of the fluid and solid cores has contributed only a small fraction of the total heat flux out of the core and has not provided an important power source for maintaining the geodynamo.
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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 | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".