Solar Wind Speed Maps from the Metis coronagraph observations
Bibliographic record
Abstract
This presentation outlines the Doppler dimming diagnostic method, the computational tools developed, and the solar wind speed maps derived from Metis data spanning a wide range of heliocentric distances, from approximately 1.5 to 10 solar radii, during the solar activity minimum.The Doppler dimming diagnostic, which combine simultaneous Metis observations from its two channels, polarized broadband visible light and narrowband ultraviolet H I Lyα intensity, allows for the measurement of the expanding coronal plasma speed. The presented wind speed maps are obtained from Metis data sets collected during the cruise phase of the Solar Orbiter mission, shortly after its first perihelion at approximately 0.5 AU in June 2020, as well as before and after its second perihelion in January and February 2021. These observations provide critical insights into the solar corona above approximately 3.0 solar radii, while future Solar Orbiter perihelion passages will extend this analysis to distances as close as 1.7 solar radii.The reliability of the derived wind speed values is evaluated, considering instrumental uncertainties, the inherent limitations of the diagnostic method, and key assumptions about solar corona model parameters, including electron and neutral atom kinetic temperatures and the 3D geometric configuration of the corona.As expected at the minimum of the solar cycle, the obtained maps show a clear bipolar topology with a rapid transition to higher speeds in the interface zone between equatorial streamers and high-latitude regions. The equatorial regions, where intense and relatively stable streamer belt persists, do not exhibit speeds higher than 220 km/s up to the maximum observed distance, around 6 solar radii. In contrast, within the coronal holes, already just above the minimum observed heights, around 3.5 solar radii, the wind speed reaches the maximum values detectable using Doppler dimming diagnostics applied to the neutral hydrogen line, approximately 350 km/s.The method and algorithms are further tested and applied to a sample of daily ultraviolet intensity images reconstructed from spectral data obtained by the UVCS instrument, in conjunction with visible light coronal observations performed by LASCO, both instruments onboard the SOHO mission during solar cycle 23. This extended analysis provides valuable insights into the solar wind acceleration region, covering distances between approximately 1.5 and 4.0 solar radii, encompassing nearly a full solar activity cycle, providing essential context to complement the present Solar Orbiter observations.
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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) | 0.002 | 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".