HF fades caused by multiple wave fronts detected by a dipole antenna in the ionosphere
Why this work is in the frame
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Bibliographic record
Abstract
An experiment on transionospheric HF propagation was carried out in 1978 using a dedicated ground transmitter at Ottawa and the sounder receivers of the ISIS 1 and ISIS 2 spacecraft. This paper deals with resulting data from ISIS 2 at 1400 km altitude. Fade frequencies of one to a few hertz on 9.303‐MHz fixed‐frequency carrier signals were measured and were found to be confined to satellite locations between about 3° and 20° equatorward of the transmitter. The majority of the fades were of the Faraday type, involving ordinary ( O ) and extraordinary ( X ) wave components. There was also a smaller number of single‐mode fades interpreted as a beat interference between two O ‐mode or two X ‐mode rays that take different routes to the spacecraft. Rays traced through model ionospheric density distributions based on tomographic data show that rays launched toward the equator are more susceptible to focusing by latitudinal periodicity than rays launched toward the pole. Such refractive effects can produce two same‐mode rays with equal intensities and different propagation directions. Swept‐frequency ionograms interleaved with fixed‐frequency measurements have also been used to model density distributions in altitude and latitude. These distributions were used iteratively with three‐dimensional ray tracing to find rays that connected the transmitter with the position of the satellite at times of interest along its path. Faraday fade rates thus predicted agree with those observed equatorward of the transmitter. Geometric optics cannot account for observed X ‐mode to O ‐mode signal ratios of at least 10 dB in other parts of the passes, ruling out deep Faraday fades. This research supports planning for coordinated ground‐space radio experiments in the upcoming Enhanced Polar Outflow Probe satellite mission.
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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 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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 it