Investigating Geomagnetic Disturbances in the Expansion Phase of Strong Substorms
Bibliographic record
Abstract
Abstract This study contributes to improved space weather forecasting by investigating geomagnetic disturbances (GMDs) associated with rapid decreases in the SuperMAG Auroral Electrojet Lower (SML) index during strong substorms (SML −500 nT) at high latitudes (64–75 MLAT). Through integrated analysis of two selected strong substorm events from December 2015, combining THEMIS and GOES‐13 spacecraft observations with ground magnetometer data from Arctic Canada and Spherical Elementary Current System (SECS) modeling, we reveal key relationships: (a) the SML drops during substorm expansion phase coincide with GMD onset and subsequent poleward propagation (64–75 MLAT); (b) SECS‐derived current patterns show intensified horizontal ionospheric currents (200 mA/m) and localized vertical current density (8–10 A/) that align spatially and temporally with the largest GMDs (reaching 25 nT/s) and (c) rapid SML decreases during substorm expansion phases correlate with dipolarization and earthward fast flows as observed by THEMIS‐A, E in the Earth's magnetotail and near‐Earth magnetic field reconfigurations with enhanced particle fluxes (GOES‐13). The horizontal current enhancements propagate coherently with the GMDs, while the SECS analysis reveals a structured vertical current density that connects magnetospheric drivers to ground‐level disturbances. These observations demonstrate a complete chain of processes from magnetotail reconfiguration to ionospheric current intensification and subsequent GMD development—a progression not typically observed in weaker substorms (SML −500 nT). Our multi‐instrument approach provides a detailed characterization of substorm‐GMD coupling, identifying key parameters that could contribute to improved forecasting.
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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 | 0.001 |
| 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".