Entropy conservation and rate of propagation of bubbles in the Earth's magnetotail: A case study
Bibliographic record
Abstract
Earthward propagation of low‐density flux tubes, called “plasma bubbles,” is a candidate mechanism to reduce total entropy in the plasma sheet. MHD models predict that bubbles conserve total entropy (S) as they propagate earthward, that the amount of density depletion governs the speed of propagation, and that bubbles slow down as their S nears the ambient plasma sheet S. The main objective of the present study is to test these predictions. Multiple instances of bursty flows with low entropy content were analyzed using in situ and all‐sky observations during a major THEMIS (TH) alignment. Twelve bubbles identified at TH‐B altitude were tracked earthward to determine if they convected past TH‐C, ‐D or ‐E and TH‐A. The analysis shows that the mean plasma sheet S along the THEMIS alignment is not conserved in general, as it decreases with decreasing distance. However, S is nearly constant along the bubbles' trajectories. Furthermore, S of the bubbles is one standard deviation smaller than the mean ambient plasma sheet S. Therefore, bubbles tend to decrease the S of the plasma sheet. An inverse relation of density and S of bubbles with velocity is consistent with theoretical predictions. The mean specific entropy (s) of the bubbles tends to be one standard deviation larger than the mean plasma sheet s. Therefore, bubbles tend to increase the plasma sheet s. A DMSP‐THEMIS coincidence during the sampled period shows how plasma measurements from low‐orbiting satellites combined with all‐sky images can be used to track the propagation of bubbles.
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 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 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".