Global Pc5 pulsations observed at unusually low L during the great magnetic storm of 24 March 1991
Bibliographic record
Abstract
Using CANOPUS, GREENLAND, IMAGE, SAMNET, and 210 MM ground‐based magnetometer array data, we examine the global characteristics of ULF waves during the onset day of the great magnetic storm of 24 March 1991. We focus on the main phase in the period of decreasing Dst and investigate the characteristics of discrete frequency Pc5 pulsations. Pc5 pulsations with multiple discrete spectral peaks including a 2.8 mHz pulsation were seen at 0815–0915 UT, and a monochromatic 1.9 mHz wave appeared at 1010–1110 UT. Also, a very monochromatic and large‐amplitude 1.7 mHz wave was observed at 1200–1340 UT across a wide range of dayside local times and at unusually low latitudes. We have analyzed the amplitude and phase relationships of waves at these frequencies. The 2.8 mHz, 1.9 mHz, and 1.7 mHz spectral peaks have maximum amplitudes at L = 3.6, L = 4, and L = 4.3, respectively, and exhibit the characteristic features of field line resonances (FLRs). The discrete mHz frequencies are consistent with some of the discrete peaks seen by Samson et al. (1992) and support the hypothesis of the existence of MHD cavity or waveguide modes in the magnetosphere. However, our results show evidence for the penetration of ULF wave power in the Pc5 band to much lower L‐values than normal, suggesting a significant reduction of the local Alfvén eigenfrequency continuum as compared to nonstorm times. This may have considerable significance for the interaction between ULF waves and MeV electrons in the outer radiation belt during storms.
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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".