Seasonal differences in the sunrise undulations at the dip equator at solar minimum at two distinct locations and their relation with postsunset electrodynamics
Bibliographic record
Abstract
Abstract A sunrise undulation (SU) is observed by ionosondes when new ionization is produced at sunrise in the upper F region at the geomagnetic equator. It creates a very quick upward transition in the F region peak altitude ( h m F 2 ), which subsequently undergoes a sharp descent at a rate far in excess of any electrodynamic drift. The peak density also increases rapidly during the descent. However, the detection of the new plasma with ionosondes is possible only if plasma from the night before has undergone enough recombination, which, on average, can vary from one location to another and one season to the next. With this in mind, we have studied seasonal variations in the SU occurrence in 2010 at two widely separated geomagnetic equatorial stations in longitude, at Jicamarca in Peru and Trivandrum in India. Noticeable differences were found in the characteristics of undulation observed at the two locations. While full undulation (both ascend and descend in h m F 2 ) was observed throughout the year at Trivandrum, only the descending part of undulation was visible at Jicamarca. Plasma density just before sunrise, on average, was 2 times larger at Jicamarca than at Trivandrum. The average h m F 2 , which peaks during night, was also higher at Jicamarca by as much as 100 km compared to Trivandrum. We traced the origin of these differences to the evolution of zonal electric field between sunset and local midnight at the two locations. The downward drift during this period was steeper at Trivandrum compared to Jicamarca, particularly during equinox. In addition, the strength of the downward drifts at Jicamarca decreased and even underwent a sign reversal prior to sunrise during equinox and winter months. In comparison, the downward motion at Trivandrum only became stronger during early morning hours. The contrast between the vertical drift at the two stations provides a very reasonable qualitative explanation for the differences in the characteristics of SU observed at the two stations.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 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 | 0.001 | 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".