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arxiv: 2604.13990 · v1 · submitted 2026-04-15 · 🌌 astro-ph.SR

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Analysis of Lyman-beta and Lyman-gamma Lines in a Pre-Eruptive and Eruptive Prominence with Solar Orbiter SPICE Observations

Yong Zhang (1) , Nicolas Labrosse (1) , Susanna Parenti (2) , Therese A. Kucera (3) ((1) SUPA School of Physics , Astronomy , University of Glasgow , Glasgow G12 8QQ UK , (2) Institut d'Astrophysique Spatiale
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Bat 121 Universit\'e Paris-Saclay/CNRS 91405 Orsay Cedex France (3) Heliophysics Science Division NASA Goddard Space Flight Center Greenbelt MD 20771 USA)
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Pith reviewed 2026-05-10 11:55 UTC · model grok-4.3

classification 🌌 astro-ph.SR
keywords solar prominencesLyman linesSPICE instrumentSolar Orbitereruptive prominencesline profilesradial velocityH alpha images
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The pith

Lyman beta and gamma line observations with SPICE show changes in density, temperature, and optical thickness in a solar prominence before and during eruption.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper demonstrates how Lyman lines captured by the SPICE instrument on Solar Orbiter can be used to derive variations in the physical conditions of a solar prominence as it transitions from a pre-eruptive to an eruptive state. By examining the integrated intensity and widths of the Lyman beta and gamma lines, the authors identify differences across prominence, disk, and coronal areas that point to evolving plasma properties. They also apply a simple geometric model to H alpha images to estimate the radial velocity in the early stages of the eruption. This approach provides a practical way to assess the Doppler contributions to the observed line profiles. Such diagnostics help in understanding the dynamics of solar plasma that can lead to space weather events.

Core claim

The central claim is that SPICE observations of the Lyman beta and Lyman gamma lines in an off-limb prominence allow the derivation of changes in physical parameters such as density, temperature, and optical thickness between pre-eruptive and eruptive phases. Spatial and temporal analysis of line profiles reveals enhanced variations during eruption, and a simple geometric model using paired 2D GONG H alpha images yields the radial velocity at the onset of eruption. This method offers a means to calculate radial velocity from two-dimensional images and accounts for potential Doppler effects in the spectra.

What carries the argument

The Lyman beta and Lyman gamma line profiles, whose integrated intensities and widths are analyzed for variations, combined with a simple geometric model applied to pairs of H alpha images to extract radial velocity.

If this is right

  • Variations in line intensity and width between regions indicate dynamic changes in prominence plasma conditions.
  • The eruption increases spatial and temporal variations in the spectral profiles.
  • Radial velocity of the prominence can be obtained from a pair of 2D images using the geometric model.
  • These observations highlight the diagnostic potential of SPICE for prominence studies, paving the way for more detailed Non-LTE modeling.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • This technique could be applied to other eruptive events observed by Solar Orbiter to build statistics on prominence velocities.
  • Combining SPICE Lyman data with other instruments might allow cross-validation of the geometric velocity estimates.
  • The approach suggests that even without full radiative transfer, basic line properties can give first-order insights into plasma evolution during eruptions.

Load-bearing premise

The assumption that a simple geometric model on paired images accurately gives the true radial velocity without major projection effects, and that line profile changes can be directly linked to density, temperature, and optical thickness variations without detailed non-LTE radiative transfer calculations.

What would settle it

A direct comparison of the geometrically derived radial velocity with independent measurements such as spectroscopic Doppler shifts from the same event or stereoscopic 3D reconstructions from multiple viewpoints would confirm or refute the velocity estimate.

Figures

Figures reproduced from arXiv: 2604.13990 by 20771 USA), (2) Institut d'Astrophysique Spatiale, (3) Heliophysics Science Division, Astronomy, Bat 121, Glasgow G12 8QQ UK, Greenbelt, MD, NASA Goddard Space Flight Center, Nicolas Labrosse (1), Susanna Parenti (2), Therese A. Kucera (3) ((1) SUPA School of Physics, Universit\'e Paris-Saclay/CNRS 91405 Orsay Cedex France, University of Glasgow, Yong Zhang (1).

Figure 1
Figure 1. Figure 1: The positions of different spacecraft. The arrow is the eruption direction of the prominence. into the physical properties and composition of the plasma within the solar atmosphere. In these observations, SPICE contributes to addressing Solar Orbiter’s Science Objective on coronal mass ejec￾tion (CME) formation through coordinated prominence observations during a dedicated 10-hour perihelion campaign. For … view at source ↗
Figure 2
Figure 2. Figure 2: The SPICE observation of the integrated intensity of the Lyman 𝛽 and Lyman 𝛾 lines taken from 07:03 - 08:09 UT, 15 April 2023. The integrated intensities along the blue cut and the green dashed cut are shown in [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 4
Figure 4. Figure 4: Left: The LW channel observation of SPICE during pre-eruption phase at 07:37:39 UT. The slit position is the same as the blue cut in [PITH_FULL_IMAGE:figures/full_fig_p004_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: The spectrum of the LW channel during pre-eruption phase at the green cross and the red cross in [PITH_FULL_IMAGE:figures/full_fig_p004_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: H𝛼 image of El Teide at 10:07 UT. The yellow arrows point to the prominence we study. The blue lines show the coordinate we use in the analysis and the red dashed lines show the cross-sections we analyze [PITH_FULL_IMAGE:figures/full_fig_p005_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: The SPICE observation of the integrated intensity of the Lyman 𝛽 from 08:13 - 11:58 UT, 15 April 2023. ’PR’ is the abbreviation of ’Prominence Region’. Prominence regions, which is around 2.5. This relatively stable ratio suggests that both lines are formed under similar radiative transfer conditions in these regions. It is a possible indication that both lines are formed through resonance scattering of th… view at source ↗
Figure 8
Figure 8. Figure 8: Up: The integrated intensity along the blue cut (x=5) for Lyman 𝛽 and Lyman 𝛾 lines during pre-eruption phase. Down: The integrated intensity along the green dashed cut (x=25) for Lyman 𝛽 and Lyman 𝛾 lines during pre-eruption phase [PITH_FULL_IMAGE:figures/full_fig_p006_8.png] view at source ↗
Figure 9
Figure 9. Figure 9: The ratio of the integrated intensity of Lyman 𝛽 and Lyman 𝛾 lines along the blue cut (x=5, left) and the green dashed cut (x=25, right) during pre-eruption phase. MNRAS 000, 1–14 (2015) [PITH_FULL_IMAGE:figures/full_fig_p006_9.png] view at source ↗
Figure 11
Figure 11. Figure 11: The average profiles of Lyman 𝛽 and Lyman 𝛾 lines of Prominence Region during pre-eruption phase along the green dashed cut in [PITH_FULL_IMAGE:figures/full_fig_p007_11.png] view at source ↗
Figure 12
Figure 12. Figure 12: The average profiles of Lyman 𝛽 in the prominence region along the blue cuts during the pre-eruption phase and eruption phase. observation in 2005, which is closer to solar minimum. On the other hand, our observations and those of Heinzel et al. (2001) are closer to solar maximum. This could explain why the integrated intensi￾ties of the prominence region for Lyman 𝛽 line in Vial et al. (2007) are much sm… view at source ↗
Figure 13
Figure 13. Figure 13: The method of line width calculation. CDF is the cumulative dis￾tribution function. The two red dashed lines lie in the locations of CDF=0.12 and CDF=0.88. The distance of the two red dashed lines is the line width of this line profile. The blue dots show data points and CDF is shown by the purple line. 2.4 Line Width Here we discuss the properties of the observed profiles without per￾forming a full decon… view at source ↗
Figure 14
Figure 14. Figure 14: The line width of Lyman 𝛽 and Lyman 𝛾 lines profiles during pre-eruption phase [PITH_FULL_IMAGE:figures/full_fig_p009_14.png] view at source ↗
Figure 15
Figure 15. Figure 15: The line width of Lyman 𝛽 lines profiles during eruption phase. The white rectangles show locations where we take samples for the disk region and the prominence region. are around 0.05–0.06 nm (the instrumental broadening of Lyman lines was neglected) for the quiescent prominences observed on May 28 and June 2, 1999, by SUMER. In Tian et al. (2009) , the line width of Lyman 𝛽 is also around 0.05 nm. These… view at source ↗
Figure 16
Figure 16. Figure 16: The Lyman 𝛽 and Lyman 𝛾 lines spectra before the eruption from image of the detector for the exposures at the raster position x=5, 10, 15, 20, 25 in [PITH_FULL_IMAGE:figures/full_fig_p010_16.png] view at source ↗
Figure 17
Figure 17. Figure 17: The Lyman 𝛽 lines spectra during eruption from image of the detector for the exposures at the raster position x=80, 82, 84, 86, 88 in [PITH_FULL_IMAGE:figures/full_fig_p010_17.png] view at source ↗
Figure 18
Figure 18. Figure 18: The Lyman 𝛽 and Lyman 𝛾 lines profiles in the prominence region from SPICE observation before the eruption. The first and second rows are the Lyman 𝛽 line profiles. The first row is pixel 410, 390, 370, 350 and 330 at 07:15:00 UT in [PITH_FULL_IMAGE:figures/full_fig_p011_18.png] view at source ↗
Figure 19
Figure 19. Figure 19: The Lyman 𝛽 lines profiles in the prominence region from SPICE observation during the eruption. The first row is pixel 360, 350, 340, 330 and 320 at 09:33:58 UT in [PITH_FULL_IMAGE:figures/full_fig_p011_19.png] view at source ↗
Figure 20
Figure 20. Figure 20: The illustration of the coordinates and angles [PITH_FULL_IMAGE:figures/full_fig_p012_20.png] view at source ↗
Figure 21
Figure 21. Figure 21: Two cross-sections of the sphere. The left one is through the dashed line (a) and the right one is through the dashed line (b) in [PITH_FULL_IMAGE:figures/full_fig_p012_21.png] view at source ↗
Figure 22
Figure 22. Figure 22: H𝛼 image of El Teide at 09:57 UT (left) and 10:17 UT (right), April 15, 2023. The filament is in the same region as [PITH_FULL_IMAGE:figures/full_fig_p013_22.png] view at source ↗
Figure 23
Figure 23. Figure 23: 19.5 nm observation of EUVI-A at 10:05 UT (left) and 10:10 UT (right), April 15, 2023. The filament is in the same region as [PITH_FULL_IMAGE:figures/full_fig_p013_23.png] view at source ↗
read the original abstract

The first dedicated observation of an off-limb prominence by the Spectral Imaging of the Coronal Environment (SPICE) instrument on board Solar Orbiter took place on April 15, 2023. Our aim is to provide an overview of the potentiality of the diagnostics using these data. We show that we can derive the changes in the physical parameters of the pre-eruptive and eruptive prominence using the Lyman lines. We investigate the integrated intensity and line widths of the Lyman $\beta$ and Lyman $\gamma$ lines, finding variations between the prominence, disk, and coronal regions. The results reflect dynamic changes in density, temperature, and optical thickness. We analyze the spatial and temporal evolution of the Lyman $\beta$ and Lyman $\gamma$ line profiles. Using a simple geometric model, we obtain the radial velocity of this prominence at the early phase of its eruption with GONG H$\alpha$ images. This offers a way of calculating the radial velocity of an eruptive filament from a pair of 2D images. The result helps us understand the potential Doppler effect in line profiles. Overall, the spectral profiles indicate that the eruption enhances spatial and temporal variations in line intensity, reflecting dynamic changes in plasma conditions within the prominence. These findings highlight the diagnostic potential of SPICE observations, and future Non-LTE radiative transfer modeling will help to further constrain prominence plasma parameters.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 0 minor

Summary. The paper presents the first dedicated SPICE observations of an off-limb prominence on 15 April 2023, analyzing Lyman-β and Lyman-γ line profiles to report variations in integrated intensity and line width between pre-eruptive and eruptive phases. These variations are interpreted as reflecting dynamic changes in density, temperature, and optical thickness. A simple geometric model applied to paired SPICE Lyman and GONG Hα 2D images is used to derive the radial velocity during the early eruption phase, with the result offered as a general method for estimating radial velocities from 2D image pairs.

Significance. If the geometric model and qualitative interpretations hold, the work demonstrates the diagnostic potential of SPICE Lyman-line observations for prominences and provides an accessible approach to radial-velocity estimation from imaging data alone. The reported spatial-temporal evolution of line profiles supplies concrete observational constraints on eruptive plasma dynamics that can guide future modeling.

major comments (2)
  1. [Abstract and §3] Abstract and §3: The simple geometric model for radial velocity is introduced without a detailed description of its construction, the assumed prominence geometry (e.g., rigid structure, negligible line-of-sight depth, uniform emissivity), or quantitative treatment of projection and line-of-sight effects. Because this model supplies the reported radial-velocity value and is used to interpret Doppler contributions to the line profiles, the lack of error propagation or sensitivity tests makes the velocity claim load-bearing and currently under-supported.
  2. [Abstract] Abstract: The statement that changes in physical parameters are derived from the Lyman lines rests on qualitative attribution of intensity and width variations to density, temperature, and optical-thickness changes. No non-LTE radiative-transfer calculations or forward-modeling results are presented to demonstrate uniqueness or to convert the observed quantities into parameter values; the manuscript defers such modeling to future work, leaving the derivation claim qualitative rather than quantitative.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their constructive and detailed comments, which have helped us improve the clarity and rigor of the manuscript. We address each major comment point by point below.

read point-by-point responses

  1. Referee: [Abstract and §3] Abstract and §3: The simple geometric model for radial velocity is introduced without a detailed description of its construction, the assumed prominence geometry (e.g., rigid structure, negligible line-of-sight depth, uniform emissivity), or quantitative treatment of projection and line-of-sight effects. Because this model supplies the reported radial-velocity value and is used to interpret Doppler contributions to the line profiles, the lack of error propagation or sensitivity tests makes the velocity claim load-bearing and currently under-supported.

    Authors: We agree that the geometric model requires a more complete description to support the reported radial velocity. In the revised manuscript we have expanded §3 with a step-by-step account of the model construction, explicit statements of the assumed geometry (rigid structure, negligible line-of-sight depth, uniform emissivity), and a quantitative discussion of projection and line-of-sight effects. We have also added error propagation and sensitivity tests to the velocity estimate. These additions directly address the load-bearing nature of the result and strengthen its use in interpreting the line profiles. revision: yes

  2. Referee: [Abstract] Abstract: The statement that changes in physical parameters are derived from the Lyman lines rests on qualitative attribution of intensity and width variations to density, temperature, and optical-thickness changes. No non-LTE radiative-transfer calculations or forward-modeling results are presented to demonstrate uniqueness or to convert the observed quantities into parameter values; the manuscript defers such modeling to future work, leaving the derivation claim qualitative rather than quantitative.

    Authors: We concur that the present analysis remains qualitative. The manuscript already notes that non-LTE radiative-transfer calculations are reserved for future work. To prevent any overstatement, we have revised the abstract and the relevant discussion in §3 to state that the observed variations in intensity and line width indicate dynamic changes in density, temperature, and optical thickness, rather than claiming quantitative derivation of specific parameter values. This revision aligns the language with the scope of the current study. revision: yes

Circularity Check

0 steps flagged

No significant circularity detected

full rationale

The paper analyzes new SPICE Lyman line observations of a prominence and applies a simple geometric model to separate GONG Hα image pairs to estimate radial velocity. Physical parameter changes are inferred qualitatively from integrated intensity and width variations in the Lyman-β and Lyman-γ lines. No derivation step reduces a reported result (velocity or parameter evolution) to a quantity fitted from the same dataset by construction, nor does any load-bearing claim rest on a self-citation chain, imported uniqueness theorem, or ansatz smuggled from prior work. The central claims remain independent of the input data reductions.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claims rest on observational data reduction and a simple geometric model whose internal parameters and projection assumptions are not enumerated in the abstract; no new physical entities are introduced.

axioms (1)
  • domain assumption Simple geometric model converts apparent 2D motion in paired images to radial velocity without significant line-of-sight confusion
    Invoked to obtain the radial velocity of the eruptive prominence

pith-pipeline@v0.9.0 · 5660 in / 1467 out tokens · 42161 ms · 2026-05-10T11:55:33.555965+00:00 · methodology

discussion (0)

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Works this paper leans on

1 extracted references · 1 canonical work pages

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    work page arXiv 2001