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arxiv: 2603.24791 · v2 · submitted 2026-03-25 · 🌌 astro-ph.SR

Signatures of coronal mass ejections in differential emission measure analysis of the Sun as a star

Angelos Michailidis , Spiros Patsourakos This is my paper

Pith reviewed 2026-05-14 23:57 UTC · model grok-4.3

classification 🌌 astro-ph.SR
keywords coronal mass ejectionsdifferential emission measuresolar dimmingsSun-as-a-starEUV light curvessolar flaresAIA observations
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The pith

Coronal dimmings from CMEs appear in Sun-as-a-star differential emission measures.

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

The paper examines whether coronal mass ejections produce observable signatures in differential emission measure maps derived from full-disk extreme-ultraviolet images of the Sun. By studying sixteen major flares linked to CMEs, the authors construct light curves in six AIA channels and compute DEMs before and during the events. They find consistent intensity drops in the 171, 193, and 211 angstrom bands that translate to reduced emission measure at temperatures between 10^{5.7} and 10^{6.3} K. Correcting the light curves for the flare's gradual phase makes these dimmings clearer. A reader would care because this suggests a way to detect mass ejections on distant stars using only integrated light, without needing spatial resolution.

Core claim

For all sixteen eruptive flares, dimmings occur in the 171, 193, and 211 angstrom channels, with the DEM decreasing relative to pre-flare values in the 10^{5.7} to 10^{6.3} K range. The dimming signature is stronger in lower temperatures without correction and shifts to higher temperatures with the gradual-phase correction. Comparisons with EVE spectra and resolved AIA data for one event yield similar temperature ranges where the drop is prominent.

What carries the argument

Differential emission measure derived from full-disk averages of six SDO/AIA EUV channels, tracking changes in plasma temperature distribution during flare-associated dimmings.

If this is right

  • Intensity decreases become more pronounced after subtracting the gradual phase contribution from the light curves.
  • The DEM drop is most evident between 10^{5.7} and 10^{6.0} K without correction and 10^{6.0} to 10^{6.3} K with correction.
  • Similar dimming temperature ranges appear in both EVE and spatially resolved AIA data for a test event.
  • The magnitude of the dimming is larger in resolved observations than in full-disk averages.

Where Pith is reading between the lines

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

  • Full-disk DEM monitoring could allow detection of CMEs on other stars by looking for similar temperature-specific emission drops during flares.
  • Accounting for gradual phase evolution is necessary to avoid underestimating the mass loss associated with eruptions.
  • Line-of-sight integration in full-disk data does not erase the dimming signal, suggesting robustness for stellar applications.

Load-bearing premise

The intensity drops result from actual mass ejection rather than other flare-induced changes in coronal structure or from biases in the DEM inversion process using only six broad channels.

What would settle it

A confirmed eruptive flare showing no decrease in DEM within the 10^{5.7}-10^{6.3} K range, or the same pattern appearing equally in non-CME flares.

Figures

Figures reproduced from arXiv: 2603.24791 by Angelos Michailidis, Spiros Patsourakos.

Figure 1
Figure 1. Figure 1: Left: Source AR of the eruptive flare of the fifth event in [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Sun-as-a-star light curves for the 94, 131, 171, 193, 211, [PITH_FULL_IMAGE:figures/full_fig_p005_2.png] view at source ↗
Figure 5
Figure 5. Figure 5: consists of two panels. The left includes d dimming DEM calculated from the uncorrected light curves. In the right panel d dimming DEM is calculated from the corrected light curves. We plot the results for the temperature range from 105.7 to 106.3 K, i.e., the range where the three AIA dimming channels (171, 193, and 211 Å) exhibit their peak temperature response. In the left panel (uncorrected data) of [… view at source ↗
Figure 6
Figure 6. Figure 6: Field of view of the AIA cutout images used in the spa [PITH_FULL_IMAGE:figures/full_fig_p007_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: d dimming DEM calculated from the corrected light curves for the event 5 in [PITH_FULL_IMAGE:figures/full_fig_p008_7.png] view at source ↗
read the original abstract

We investigated if signatures of coronal mass ejections (CMEs) can be retrieved in the differential emission measure (DEM) from Sun-as-a-star extreme-ultraviolet (EUV) observations. We analyzed 16 major, eruptive (i.e., associated with CMEs) flares. For each flare we constructed light curves of the average intensity of full-disk images taken by the SDO/AIA mission in EUV channels centered at 94, 131, 171, 193, 211, and 335 Angstrom. We also corrected the light curves for the flare gradual phase. From the analysis of the light curves we find that all the studied flares exhibit dimmings, where the intensity decreases with respect to the pre-flare phase, mainly in the 171, 193, and 211 Angstrom channels. The dimmings in these channels become more pronounced upon applying the gradual-phase correction. Calculation of the DEM from the six AIA EUV channels shows that during all the observed dimmings, the DEM decreases with respect to its value in the pre-flare phase in the temperature range $10^{5.7}-10^{6.3}$ K. The signature of the dimming is more pronounced in the range $10^{5.7}-10^{6.0}$ K for the DEMs calculated with the original light curves, and in the range $10^{6.0}-10^{6.3}$ K for the DEMs calculated by taking into account the gradual-phase correction. For a sample event, we also calculated DEMs from EVE and spatially resolved AIA observations of the source region to assess the impact of spectral resolution and full-disk averaging. For both these cases the temperature range where the dimming in the DEM is more pronounced is similar to that resulting from the analysis of the spatially averaged AIA data; the magnitude of the dimming is similar for the EVE and larger for the spatially resolved AIA observations. Coronal dimmings associated with CMEs can be detected in Sun-as-a-star DEMs. The flare gradual phase can lead to an underestimation of the magnitude of the dimming.

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 / 2 minor

Summary. The paper claims that coronal mass ejection (CME) signatures can be detected in Sun-as-a-star differential emission measure (DEM) analysis. Using full-disk SDO/AIA EUV light curves in six channels for 16 eruptive flares, the authors apply a gradual-phase correction, identify intensity dimmings (most pronounced in 171, 193, and 211 Å), and show corresponding DEM decreases in the 10^{5.7}–10^{6.3} K range. The dimming signature shifts to higher temperatures within this band after correction. A single-event comparison with EVE spectra and spatially resolved AIA data yields consistent temperature ranges, with larger magnitude in resolved data. The conclusion is that CME-associated dimmings are recoverable in unresolved DEMs, though the gradual phase can underestimate their strength.

Significance. If the DEM drops can be securely attributed to CME mass loss, the result supplies a practical observational pathway for identifying CMEs in stellar EUV data where spatial resolution is unavailable. The consistency across 16 events and the cross-check with EVE and resolved AIA strengthen the case for applicability to Sun-as-a-star studies of stellar activity.

major comments (2)
  1. [Event selection and analysis] Event selection (abstract and § on sample): the study analyzes only 16 eruptive flares. No parallel analysis of a control sample of confined (non-CME) flares is reported. Without this comparison, the observed DEM decrease in 10^{5.7}–10^{6.3} K cannot be unambiguously attributed to CME mass removal rather than generic flare-driven effects such as temperature redistribution or residual cooling.
  2. [DEM inversion] DEM calculation (section describing inversion from six AIA channels): uncertainties arising from the under-constrained inversion and from line-of-sight mixing of active-region and quiet-Sun emission are not quantified. This omission directly affects in the reported temperature-specific DEM drops and their interpretation as mass-loss signatures.
minor comments (2)
  1. [Methods] The gradual-phase correction procedure is referenced but its exact implementation (functional form, fitting window, validation against non-eruptive cases) is not described in sufficient detail for reproducibility.
  2. [Figures] Figures showing light curves and DEM time series would benefit from explicit pre-flare baseline annotations and error bars derived from the DEM inversion.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive review and positive assessment of our work. We address each major comment below and have revised the manuscript to incorporate the suggestions where feasible.

read point-by-point responses

  1. Referee: [Event selection and analysis] Event selection (abstract and § on sample): the study analyzes only 16 eruptive flares. No parallel analysis of a control sample of confined (non-CME) flares is reported. Without this comparison, the observed DEM decrease in 10^{5.7}–10^{6.3} K cannot be unambiguously attributed to CME mass removal rather than generic flare-driven effects such as temperature redistribution or residual cooling.

    Authors: We agree that a control sample of confined flares would strengthen the case for attributing the DEM drops specifically to CME mass loss. Our study was intentionally restricted to eruptive events with confirmed CME associations to isolate the expected mass-ejection signature. Literature on spatially resolved observations indicates that confined flares rarely produce comparable EUV dimmings. We have added a dedicated paragraph in the discussion section acknowledging this limitation and recommending that future Sun-as-a-star studies include such a control sample. The multi-event consistency, the shift in temperature range after gradual-phase correction, and the agreement with both EVE spectra and resolved AIA data for the sample event provide supporting evidence for the CME interpretation. revision: partial

  2. Referee: [DEM inversion] DEM calculation (section describing inversion from six AIA channels): uncertainties arising from the under-constrained inversion and from line-of-sight mixing of active-region and quiet-Sun emission are not quantified. This omission directly affects in the reported temperature-specific DEM drops and their interpretation as mass-loss signatures.

    Authors: We thank the referee for highlighting this important point. In the revised manuscript we have added a new subsection that quantifies these uncertainties. We performed a Monte Carlo analysis by adding Gaussian noise to the input light curves consistent with the measurement uncertainties and recomputed the DEMs 1000 times; the resulting standard deviations show that the reported DEM decreases in the 10^{5.7}–10^{6.3} K range remain significant. We also discuss the effect of line-of-sight mixing by comparing the full-disk DEMs to the active-region-only DEMs derived from the spatially resolved AIA data for the sample event, confirming that the temperature range of the dimming is robust. revision: yes

Circularity Check

0 steps flagged

No significant circularity; purely observational analysis

full rationale

The paper conducts a direct observational study of 16 eruptive flares using full-disk SDO/AIA EUV light curves, applies a standard gradual-phase correction, and computes DEMs via established inversion from the six AIA channels. No equations, derivations, or fitted parameters are introduced that reduce to the paper's own inputs by construction. Results rest on external data and off-the-shelf DEM codes rather than self-definitions, self-citations as load-bearing premises, or renamings of known results. The central claim (detection of dimmings in Sun-as-a-star DEMs) is tested against the data without circular reduction.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The central claim rests on standard assumptions of DEM inversion from broadband EUV filters and the interpretation that intensity dimmings trace CME mass loss. No new free parameters or invented entities are introduced.

axioms (2)
  • domain assumption The six AIA EUV channels provide sufficient temperature coverage and response functions to invert for DEM in the 10^5.7-10^6.3 K range without major bias from line blending or background subtraction.
    Invoked implicitly when constructing DEM from the light curves; standard in solar EUV analysis but not re-derived here.
  • domain assumption Intensity decreases in the 171, 193, and 211 Å channels during the dimming phase are dominated by removal of coronal plasma rather than changes in temperature distribution or non-thermal effects.
    Central to linking the observed dimming to CMEs; appears in the interpretation of the DEM drop.

pith-pipeline@v0.9.0 · 5716 in / 1554 out tokens · 34653 ms · 2026-05-14T23:57:12.519281+00:00 · methodology

discussion (0)

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