Solar Flare‐Induced Gradient Drift Instability Observed by SuperDARN HF Radars
Bibliographic record
Abstract
Abstract Solar flares are a rapid increase in solar irradiance, specifically in X‐ray and Extreme Ultraviolet spectra, which enhances the ionization in the dayside ionosphere and creates Sudden Ionospheric Disturbances (SIDs). SIDs are known to create space weather impacts on traveling high frequency (HF: 3–30 MHz) radio waves, by disrupting the communication channels. In this study, we examine ionospheric scatters at dawn terminator, which stems from a severe X9.3 flare on 6 September 2017 peaked at 12:02 UT, utilizing SuperDARN HF coherent scatter radars and Global Navigation Satellite System (GNSS) Total Electron Content (TEC) observations. Specifically, we are interested in the transients in the ionospheric electrodynamics at the sub‐auroral latitude near the terminator stemming from the flare effect. Observations suggest that flare‐induced density gradient likely favors the formation of gradient‐drift instability near the dawn terminator, leading to the irregularities observed by the SuperDARN radars with line‐of‐sight (LoS) Doppler velocity reaching nearly 300 m/s. The flare amplifies the eastward TEC gradient near the dawn terminator by approximately 2–3 times compared to a geomagnetically quiet and non‐flare day. The observed irregularities, attributed to flare‐driven instabilities, exhibit a velocity consistent with the equatorial return flow of ionospheric Hall convection. In contrast to prior studies indicating decreased cross‐polar‐cap potential and associated ionospheric convection flow, our findings show the flare is followed by an increase in localized electric field near the dawn terminator, as depicted in radar LoS velocity.
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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".