The Ionospheric Leg of the Substorm Current Wedge: Combining Iridium and Ground Magnetometers
Bibliographic record
Abstract
Utilising magnetic field measurements made by the Iridium satellites and by ground magnetometers in North America we calculate the full ionospheric current system and investigate the substorm current wedge. The current estimates are independent of ionospheric conductance, and are based on estimates of the divergence-free (DF) ionospheric current from ground magnetometers and curl-free (CF) ionospheric currents from Iridium. The DF and CF currents are represented using spherical elementary current systems (SECS), derived using a new inversion scheme that ensures the current systems’ spatial scales are consistent. We present 18 substorm events and find a typical substorm current wedge (SCW) in 12 events. Our investigation of these substorms shows that during substorm expansion, equivalent field-aligned currents (EFACs) derived with ground magnetometers are a poor proxy of the actual FAC. We also find that the intensification of the westward electrojet can occur without an intensification of the FACs. We present theoretical investigations that show that the observed deviation between FACs estimated with satellite measurements and ground-based EFACs are consistent with the presence of a strong local enhancement of the ionospheric conductance, similar to the substorm bulge. Such enhancements of the auroral conductance can also change the ionospheric closure of pre-existing FACs such that the ground magnetic field, and in particular the westward electrojet, changes significantly. These results demonstrate that attributing intensification of the westward electrojet to SCW current closure can yield false understanding of the ionospheric and magnetospheric state.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 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".