Five Years of Pulsar Flux Density Monitoring: Refractive Scintillation and the Interstellar Medium
Bibliographic record
Abstract
We have monitored the radio flux density of 21 pulsars on a daily basis for five years. The 610 MHz flux density time series for these pulsars range from nearly constant for the most distant and heavily scattered pulsars to rapidly varying, saturated time series for more nearby pulsars. The measured stability of the flux density from the most distant pulsars (variations less than 5%) implies that the average radio emission from pulsars, before it has been affected by propagation through the interstellar medium, is constant in strength on timescales of a few hours to several years. The modulation index of the flux density variations never exceeds 0.5, ruling out a density inhomogeneity spectrum with a steep power-law exponent (β > 4). The flux density variations for 15 of the pulsars are consistent with a Kolmogorov turbulence spectrum over a range of more than 5 orders of magnitude in scattering strength, with no detectable presence of an inner scale. For these lines of sight we constrain the inhomogeneity slope to be in the range 3.5 ≤ β ≤ 3.7, which brackets the Kolmogorov value of β = 3.67. The flux density variations are greater than predicted by this model for six pulsars—including the Crab and Vela—but this group is consistent with a Kolmogorov spectrum and an inner scale of ≈10 10 cm. The lines of sight to three of the other pulsars in this group pass through H II regions around young, hot stars. For six pulsars we have found a change in the slope of the intensity structure function, which could be connected with a change in the slope of the inhomogeneity power spectrum at a scale of ≈10 13 cm.
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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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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 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".