Ion temperature drop and quasi‐electrostatic electric field at the current sheet boundary minutes prior to the local current disruption
Bibliographic record
Abstract
From a survey of the cross‐tail current disruption (CD) events in the near‐Earth plasma sheet collected from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission, we identify a highly repeatable class of event occurring at the current sheet boundary in a few minutes before the local CD onset. Salient features of this class of event include (1) a precipitous drop of the ion temperature, (2) concurrent growth of a neutral sheet‐pointing electric field, and (3) ULF wave activations at Pi1/Pi2 bands. We interpret the ion temperature drop as a manifestation of the extremely thinning of the local current sheet prior to its disruption. This thinning process is inferred as nonadiabatic by nature. Particularly, when the current sheet thickness is down to ion kinetic scales, the ions are demagnetized, and a quasi‐electrostatic neutral sheet‐pointing electric field emerges owing to the charge separation. The ULF fluctuations of electric/magnetic field have a two‐band structure. The lower‐frequency band with a period of 50 to 80 s is interpreted as an Alfvenic mode coupled from other preonset wave modes excited at the equatorial plasma sheet such as the ballooning. The higher‐frequency wave at 10‐ to 20‐s periods is attributed to some instability mode, directly leading to the disruption of the thin current sheet (TCS). We suggest that an extremely thinned non‐Harris TCS and the emergence of quasi‐electrostatic field constitute the conducive conditions for a local CD to occur. A companion paper by Liu et al. (2009) covers some theoretical aspects of this study.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 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) | 0.001 | 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".