Evolution and characteristics of global Pc5 ULF waves during a high solar wind speed interval
Bibliographic record
Abstract
We present an interval of extremely long‐lasting narrow‐band Pc5 pulsations during the recovery phase of a large geomagnetic storm. These pulsations occurred continuously for many hours and were observed throughout the magnetosphere and in the dusk‐sector ionosphere. The subject of this paper is the favorable radial alignment of the Cluster, Polar, and geosynchronous satellites in the dusk sector during a 3‐hour subset of this interval that allows extensive analysis of the global nature of the pulsations and the tracing of their energy transfer from the solar wind to the ground. Virtually monochromatic large‐amplitude pulsations were observed by the CANOPUS magnetometer chain at dusk for several hours, during which the Cluster spacecraft constellation traversed the dusk magnetopause. The solar wind conditions were very steady, the solar wind speed was fast, and time series analysis of the solar wind dynamic pressure shows no significant power concentrated in the Pc5 band. The pulsations are observed in both geosynchronous electron and magnetic field data over a wide range of local times while Cluster is in the vicinity of the magnetopause providing clear evidence of boundary oscillations with the same periodicity as the ground and geosynchronous pulsations. Furthermore, the Polar spacecraft crossed the equatorial dusk magnetosphere outside of geosynchronous orbit ( L ∼ 6–9) and observed significant electric and magnetic perturbations around the same quasi‐stable central frequency (1.4–1.6 mHz). The Poynting vector observed by the Polar spacecraft associated with these pulsations has strong field‐aligned oscillations, as expected for standing Alfvén waves, as well as a nonzero azimuthal component, indicating a downtail component to the energy propagation. In the ionosphere, ground‐based magnetometers observed signatures characteristic of a field‐line resonance, and HF radars observed flows as a direct consequence of the energy input. We conclude that the most likely explanations is that magnetopause oscillations couple energy to field lines close to the location of Polar, setting up standing Alfvén waves along the resonant field lines which are then also observed in the ionosphere. In the absence of monochromatic dynamic pressure variations in the solar wind, this event is a potential example where discrete frequency pulsations in the magnetosphere result from the excitation of a magnetospheric waveguide mode, perhaps excited via the Kelvin‐Helmoltz instability or via overreflection at the duskside magnetopause.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 | 0.001 |
| 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 teacher head, 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".