Substorm onset and expansion phase intensification precursors seen in polar cap patches and arcs
Bibliographic record
Abstract
Localized, transient polar cap flows impinging on the poleward boundary of the nightside auroral oval have been suggested to precede poleward boundary intensifications (PBIs), which are often followed by auroral streamers, some of which propagate equatorward and appear to lead to substorm auroral onset. While echo coverage often limits radar flow measurements, imaging of polar cap patches and arcs has the potential to monitor localized polar cap flows by tracing emission structures, previously associated with enhanced flows, over long distances. We use such imaging to examine if polar cap patches and arcs moving over large distances can be seen as possible precursors to presubstorm‐onset PBIs. We find evidence that such features, which are longitudinally narrow, propagate from the dayside polar region toward the nightside polar cap boundary prior to pre‐onset PBIs. This sequence indicates that transient activity in the dayside polar region may initiate polar cap patches and arcs that propagate across the polar cap and are followed by pre‐onset PBIs. Furthermore, we find evidence that expansion‐phase active aurora expanded poleward soon after additional polar cap patches and arcs reached close to the nightside polar cap boundary. The expansion phase auroral activity significantly weakened when polar cap patches/arcs disappeared. Our findings suggest that plasma transport originating from the dayside and reaching the nightside open‐closed boundary may trigger in plasma sheet flow bursts and play a crucial role in pre‐ and post‐onset auroral activity. Polar cap imaging offers the possibility for monitoring such localized, transient plasma transport over large distances.
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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 | 0.000 | 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".