{"id":"3f790633-eef8-4c9b-b8c5-2dcec2d51517","arxiv_id":"2506.06126","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":4,"one_line_summary":"Simultaneous Hi-C 2.1 and SDO/AIA observations of slow waves in one coronal loop yield consistent damping lengths, showing no instrument-dependent difference in this case.","lead":"Using two solar telescopes that watched the same active region at the same time, the authors measured the periods, speeds, and damping lengths of slow magneto-acoustic waves in a coronal loop and found that the two instruments agree on the damping lengths. The result adds a data point to an open puzzle about why a previous instrument pair reported very different damping lengths.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The null result may be an artifact of comparing AIA's 30-minute, 5-minute-smoothed analysis with Hi-C's 5-minute, mean-subtracted analysis; recomputing AIA on the common 5-minute window would settle it.","rationale":"The reader identified the same weakest assumption: the comparability of amplitude profiles given different background subtraction and time-series lengths. I agree this is the most load-bearing concern because the paper's central claim is a null result, and a null result is only meaningful if the two measurements are of the same physical quantity. The AIA analysis uses a 30-minute time series and a 5-minute smoothed background, while Hi-C uses a 5-minute series and a full-duration mean. If the wave amplitude or background evolves over 30 minutes, the AIA standard deviation (ATM) or the chosen snapshot (PTM) represents a different averaging than the Hi-C measurement. The issue is concrete and testable: restricting AIA to the common 5-minute window with a matching background construction would reveal whether the agreement in damping lengths survives. The paper is otherwise careful: it acknowledges the single-loop limitation, uses two independent methods, and provides error estimates. The large AIA uncertainties are a limitation but not a fatal flaw. Thus the reader's CONDITIONAL verdict remains appropriate; no change is needed. I considered other potential issues, such as the arbitrary choice of C in the ATM fit (Section 3.3.2) and the short Hi-C series for Fourier periods, but these apply similarly to both instruments and do not threaten the comparison as directly as the non-stationarity concern.","tokens_in":9283,"tokens_out":7851,"duration_ms":78477,"concrete_test":"Recompute the AIA damping lengths (PTM and ATM) using only the 5-minute interval overlapping the Hi-C observations, with the background constructed as the full-duration mean of that interval (mirroring the Hi-C procedure). If the resulting AIA damping lengths shift by more than their quoted uncertainties (e.g., PTM outside 4.0±2.1 Mm) or no longer agree with Hi-C within 1 sigma, the null result is not robust to analysis choices. Additionally, compute the AIA ATM amplitude profile with a sliding 5-minute window over the full 30-minute series; if the derived damping length varies by more than the quoted error, the use of the full-series standard deviation is not representative.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim (no notable difference in damping lengths between AIA and Hi-C) rests on comparing quantities that are not constructed from the same data interval. In Section 3, the AIA background is a 5-minute running mean over a 30-minute series, while the Hi-C background is the mean over its ~5-minute series. In Section 3.3.2 (ATM), the AIA amplitude is the standard deviation over ~29 minutes, whereas the Hi-C amplitude is the standard deviation over ~4.25 minutes. If the wave amplitude or background is not stationary over 30 minutes, the AIA amplitude profile is a time-averaged quantity that need not equal the instantaneous amplitude during the simultaneous 5-minute Hi-C window. The same issue affects the PTM snapshot (Section 3.3.1), because the AIA detrended map is generated with a different background filter. Thus the reported consistency (4.0±2.1 vs 4.1±0.3 Mm from PTM; 3.4±1.0 vs 3.7±0.1 Mm from ATM) could reflect the different effective time averaging rather than a true absence of instrument-dependent damping. The large AIA uncertainties further limit the power of this null test.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper analyzes cotemporal observations of a fan loop in NOAA AR12712 obtained with Hi-C 2.1 and SDO/AIA, searching for propagating slow magneto-acoustic waves. The authors detect oscillations in both instruments, measure period, propagation speed, and damping length using two methods (PTM and ATM), and report that the damping lengths are consistent within uncertainties: 4.0±2.1 Mm versus 4.1±0.3 Mm from PTM and 3.4±1.0 Mm versus 3.7±0.1 Mm from ATM for AIA and Hi-C, respectively. They conclude that there is no notable instrument-dependent difference in damping lengths, in contrast to the recent result of Meadowcroft et al. (2024). The paper is based on a single loop and a single 5-minute Hi-C time series.","tokens_in":9530,"tokens_out":6258,"duration_ms":63677,"significance":"If the null result holds up, the paper is a valuable data point suggesting that the instrument-dependent damping lengths reported by Meadowcroft et al. (2024) may not be a universal feature of slow-wave observations, and it would support the idea that some of the discrepancy could be due to passband or viewing-angle effects in that particular pair. The paper also appears to be the first to report slow magneto-acoustic waves in Hi-C 2.1 data, and it gives a careful treatment of photon-noise and readout-noise error propagation in Appendix A, and it explicitly discusses limitations such as the short Hi-C series and localized brightenings. However, the central comparison is weakened by the fact that the AIA and Hi-C amplitude profiles are constructed from very different time intervals and background definitions, and the large AIA uncertainties limit the power of the null test. With a corrected AIA analysis over the common 5-minute window, the result could become a solid contribution; without that, the 'no difference' claim is not yet fully supported.","major_comments":[{"comment":"The AIA and Hi-C damping lengths are not estimated from comparable quantities. The AIA background is a 5-minute running mean over a 30-minute series, while the Hi-C background is an average over the full ~5-minute duration; likewise, the ATM standard deviation is computed over ~29 minutes for AIA and over ~4.25 minutes for Hi-C. If the wave amplitude or background is not stationary over 30 minutes, the AIA amplitude profile used in Eq. (2) and the AIA phase-tracking profile are time-averaged quantities that need not represent the instantaneous oscillation state during the simultaneous 5-minute window. The reported consistency (4.0±2.1 vs 4.1±0.3 Mm from PTM; 3.4±1.0 vs 3.7±0.1 Mm from ATM) could therefore reflect different effective time averaging rather than a genuine absence of instrument-dependent damping. The authors should recompute the AIA analysis using only the 5-minute overlap period and the same background construction as Hi-C, and report whether the damping lengths remain consistent.","section":"Section 3, background subtraction; Section 3.3.2"},{"comment":"The ATM damping length depends on the offset constant C, which is fixed as the amplitude at the last spatial position at about 12 Mm, a region where the oscillations are not visible and the signal is essentially noise. The fit itself is restricted to distances up to 7 Mm, so C essentially sets the asymptotic noise floor. The authors do not explore the sensitivity of Ld to this choice, and the quoted errors do not include the uncertainty in C. A different but plausible choice of C (for instance, the mean noise level or a free parameter) could shift Ld by an amount comparable to the quoted uncertainties. I ask the authors to vary C within a reasonable range and show how Ld changes, or to propagate the uncertainty in C into the reported errors.","section":"Section 3.3.2, Eq. (2)"},{"comment":"The Hi-C PTM and ATM errors are surprisingly small (0.3 Mm and 0.1 Mm) given that the Hi-C time series covers only about two wave cycles (304 s with a period of approximately 2.8 min). These formal fit errors do not include systematic contributions from the short time series, the manual selection of the ridge in the phase-tracking method, the choice of the excluded first 45 s, or the different background subtraction discussed above. The statement that the damping lengths agree is therefore driven largely by the much larger AIA uncertainties (2.1 Mm in PTM, 1.0 Mm in ATM), which makes the comparison low in statistical power. The authors should provide a systematic error budget for the Hi-C values or at least clearly caution against interpreting the small formal errors as evidence for a tight constraint.","section":"Section 3.3.1 and Table 1"},{"comment":"The conclusion that there is no notable difference in damping lengths is a single-loop, single-event null result. Given that the AIA PTM error is more than half of the measured value (4.0±2.1 Mm), the test has limited ability to detect a difference of the magnitude reported by Meadowcroft et al. (2024) (6.9 vs 12.8 Mm). The authors should explicitly state this low statistical power in the conclusions rather than presenting the null result as a robust finding. This limitation is acknowledged indirectly in the text, but it should be made prominent because it directly affects the interpretation of the comparison.","section":"Section 4 (Discussion and Conclusions)"}],"minor_comments":[{"comment":"There are typographical errors: 'oscillatons' should be 'oscillations' and 'Addtionally' should be 'Additionally'; in Section 4, 'quantise' should be 'quantify'.","section":"Section 3, paragraph 1"},{"comment":"The statement that AIA data were calibrated using 'a robust pipeline developed by Rob Rutten' should include a reference or a footnote to the pipeline, since the reader cannot otherwise verify the calibration details.","section":"Section 2, paragraph 2"},{"comment":"The Hi-C gain is assumed to be unity because it is not provided in the instrument documentation; this assumption directly affects the error bars in Figures 4 and 5 and should be justified or tested, for example by checking how the derived damping lengths change if the gain is varied by a factor of two.","section":"Appendix A"},{"comment":"Panel (b) is described as the AIA time-distance map in the duration overlapping Hi-C, but it is not clear whether this panel is simply a temporal crop of the full 30-minute detrended map (with a 5-minute running-mean background) or whether it was re-detrended using only the 5-minute interval. This distinction is central to the analysis and should be stated explicitly in the caption or in the text.","section":"Figure 2 caption"},{"comment":"The derivation of the 21-degree inclination angle from the ratio of the observed propagation speed to the nominal sound speed assumes that the loop is straight and that the wave propagates exactly along the loop axis; the projection correction should be described as an assumption, since loop curvature and off-axis propagation could affect the inferred angle.","section":"Section 3.2"}],"recommendation":"major_revision","confidential_remarks":"The central claim is a null result, and the comparison is currently compromised by the inconsistent time windows and background constructions between the AIA and Hi-C analyses. This is fixable within the scope of the paper: the authors should recompute the AIA damping lengths using only the overlapping 5-minute interval and the same background definition as Hi-C, and they should address the sensitivity of the ATM offset constant. If the consistency persists under those conditions, the paper could be acceptable after a moderate revision; if not, the conclusions would need to be substantially revised. I therefore recommend major revision rather than rejection."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"X,\n\nThe genuinely new thing: first detection of propagating slow magneto-acoustic waves in Hi-C 2.1, and the first simultaneous Hi-C/AIA comparison of damping lengths. That makes it a direct counterpoint to Meadowcroft et al. (2024), who found a large instrument-dependent damping-length difference between EUI and AIA. Here the authors get consistent values from both instruments using two standard methods (PTM: 4.0±2.1 vs 4.1±0.3 Mm; ATM: 3.4±1.0 vs 3.7±0.1 Mm).\n\nCredit where due: the coalignment is careful, the noise model for the error bars is sensible, and the limitations are stated openly. The short Hi-C duration is acknowledged when it explains the broad period uncertainty (2.8±1.2 min vs 2.7±0.2 min). The paper does not oversell a single-loop result.\n\nNow the soft spots, in order of importance. First, the AIA PTM uncertainty is so large that the PTM comparison has essentially no discriminating power. The ATM comparison is tighter, but there is a more basic problem: the two datasets are analyzed on different time baselines. For AIA, the background is a 5-minute running mean on a 30-minute series and the ATM amplitude is the standard deviation over about 29 minutes; for Hi-C, the background is the mean of a 5-minute series and the ATM uses about 4.25 minutes. If the wave amplitude or background is not stationary over 30 minutes, the AIA amplitude profile is a time-averaged quantity and need not represent the same oscillatory state as the Hi-C window. The same filter mismatch affects the PTM snapshot. This is a real concern, and the stress-test suggestion is right: recompute the AIA analysis on the common 5-minute window, or at least show that the amplitude profile is stable across the 30 minutes. Without that, the null result is suggestive but not conclusive.\n\nThis is one loop, one event. The authors say so themselves. They frame the paper as a data point, which is the right tone. No code is provided, but the analysis steps are described well enough to reproduce the key numbers.\n\nBottom line: a careful, honest observational comparison that deserves a serious referee, not a desk rejection. I would send it to review and ask the authors to address the time-window mismatch, ideally with the suggested consistency check. Once that is done, the paper will be a solid, if modest, contribution to the damping-length debate.\n\nRegards,","headline":"First Hi-C 2.1 slow-wave detection shows damping lengths consistent with AIA, but the comparison is weakened by different time windows and a very uncertain AIA phase-tracking fit.","tokens_in":10050,"tokens_out":3152,"would_cite":false,"duration_ms":29590,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"Damping lengths of slow magneto-acoustic waves in the same coronal loop agree between SDO/AIA and Hi-C 2.1 within uncertainties, indicating that a recently reported instrument-dependent difference does not generalize.","keywords":["slow magneto-acoustic waves","coronal fan loops","damping length","SDO/AIA","Hi-C 2.1","phase tracking method","amplitude tracking method","sunspot loops"],"falsifier":"Re-run the amplitude-tracking analysis using only the AIA data that overlap the Hi-C window, with the same flat background and the same 5-minute series length used for Hi-C: if the resulting $L_d$ leaves the quoted $3.4\\pm1.0$ Mm uncertainty, the cross-instrument agreement depends on series length or background choice; if it stays near 3.7 Mm, the null result holds.","tokens_in":9075,"feed_emoji":"🌞","tokens_out":12696,"duration_ms":107841,"temperature":0.7,"pith_summary":"This paper asks whether the measured damping length of slow magneto-acoustic waves in a coronal loop depends on the telescope that observes it, using simultaneous observations of the same loop in active region AR12712 made by SDO/AIA at 171 Å and the sounding-rocket Hi-C 2.1 at 172 Å. The two instruments return consistent wave properties: periods of $2.7\\pm0.2$ min and $2.8\\pm1.2$ min, propagation speeds of $46.0\\pm1.7$ km s$^{-1}$ and $48.1\\pm0.6$ km s$^{-1}$, and damping lengths that agree within uncertainties in both estimation methods ($4.0\\pm2.1$ Mm vs $4.1\\pm0.3$ Mm by phase tracking, $3.4\\pm1.0$ Mm vs $3.7\\pm0.1$ Mm by amplitude tracking). The authors read this agreement as evidence that a recently reported large difference in damping lengths between EUI and AIA is not a universal instrumental effect. If the result holds, the cause of that earlier discrepancy must lie in the particular instrument pair, its passband responses, or its viewing geometry rather than in the waves themselves.","feed_headline":"Two solar telescopes agree on wave damping lengths","feed_subtitle":"The same coronal loop decays over about 4 Mm in both AIA and Hi-C 2.1, challenging a reported instrument effect.","key_machinery":"The quantitative engine is the damping length $L_d$, the distance over which the wave amplitude falls by a factor of $e$, estimated by two independent fitting procedures on time-distance maps built along the same loop. The Phase Tracking Method takes the spatial intensity profile at one chosen time step and fits it to an exponentially damped sinusoid, $I(x)=A_0 e^{-x/L_d}\\sin(2\\pi x/\\lambda+\\phi)+B_0+B_1 x$. The Amplitude Tracking Method converts the temporal standard deviation at each position into an amplitude through $A=\\sqrt{2}\\sigma$ and fits $A(x)=A_0 e^{-x/L_d}+C$, with $C$ fixed to the amplitude at the last usable position. Strict coalignment of the Hi-C frames to AIA (roll-angle correction, upscaling, and cross-correlation shifts, following a published procedure) ensures both instruments sample the same loop pixels, and it is the comparison of $L_d$ across instruments—rather than any single absolute value—that carries the argument.","core_discovery":"On the paper's own terms, the central discovery is a null comparison: for the single loop in which slow magneto-acoustic waves are clearly visible in both datasets, the damping length inferred from Hi-C 2.1 equals that inferred from SDO/AIA within the measurement uncertainties. Phase tracking yields $L_d = 4.0\\pm2.1$ Mm for AIA and $4.1\\pm0.3$ Mm for Hi-C; amplitude tracking yields $3.4\\pm1.0$ Mm and $3.7\\pm0.1$ Mm, respectively, so the two instruments also agree with each method. The oscillations share a period near 2.7–2.8 min and propagation speeds of $46.0\\pm1.7$ km s$^{-1}$ and $48.1\\pm0.6$ km s$^{-1}$, and they fade beyond about 7 Mm from the loop footpoint in both datasets. The paper also reports the first detection of propagating slow waves in Hi-C 2.1 data and uses the agreement to argue that instrument choice alone need not alter measured damping lengths.","pith_inferences":["Editorial inference: the null result shifts the burden of explanation for the EUI/AIA discrepancy onto that specific setup—e.g., the marginal difference in passband temperature response or the 19° viewing-angle separation—but this paper's data cannot distinguish those possibilities.","Editorial inference: the amplitude-tracking comparison is the weakest link in the chain, because AIA's amplitude profile comes from a 30-minute series with a 5-minute smoothed background while Hi-C's comes from a 5-minute series with a flat average; a longer Hi-C observation or a matched-window AIA analysis would test whether this procedural mismatch is masking a real difference.","Editorial inference: a natural numerical extension is to feed synthetic time-distance maps with known input $L_d$ and the two different series lengths through the PTM and ATM pipelines, which would quantify how much of the agreement (and of the EUI/AIA contrast) is caused by series length and background choice rather than by the waves."],"forward_implications":["The AIA and Hi-C damping lengths agree within uncertainties in both methods, so the large EUI-versus-AIA discrepancy reported elsewhere does not appear to be a universal property of cross-instrument slow-wave measurements.","The two fitting methods also agree with each other within each dataset, indicating the measured decay is not an artefact unique to one fitting procedure.","Because the damping length ($\\sim4$ Mm) is comparable to the fitted wavelength ($\\sim4.7$ Mm) and the oscillations vanish within about 7 Mm, these observations reinforce the picture of rapid, wavelength-scale damping of slow waves in sunspot-rooted loops.","The first identification of propagating slow waves in Hi-C 2.1 data means short-duration, high-resolution sounding-rocket observations can contribute to wave studies when guided by cotemporal AIA data."],"supporting_citations":[{"why":"Supplies the prior report of distinct damping lengths for EUI and AIA that motivates this cross-instrument check.","marker":"Meadowcroft et al. (2024)"},{"why":"Defines the Hi-C 2.1 instrument, its 172 Å passband, plate scale, cadence, and readout noise used in the analysis.","marker":"Rachmeler et al. (2019)"},{"why":"Defines AIA, including the 171 Å channel characteristics, cadence, and plate scale used for the comparison.","marker":"Lemen et al. (2012)"},{"why":"Provides the phase-tracking and amplitude-tracking methods that the paper applies to both datasets.","marker":"Krishna Prasad et al. (2019)"},{"why":"Established the rapid damping of propagating slow waves in coronal loops, the observable whose measured length scale is compared here.","marker":"De Moortel et al. (2002b)"},{"why":"Gives a stereoscopically deprojected damping length reference point for comparing slow-wave decay across different vantage points.","marker":"Marsh et al. (2011)"},{"why":"Provides an earlier same-passband, two-spacecraft measurement whose damping lengths agreed within large uncertainties.","marker":"Marsh et al. (2009)"},{"why":"Supplies the AIA gain and readout noise used in the uncertainty estimates that set the error bars on the damping lengths.","marker":"Boerner et al. (2012)"},{"why":"Supplies the cross-correlation coalignment procedure used to ensure both instruments sample the same loop.","marker":"Warren et al. (2020)"},{"why":"Documents the marginal temperature-response difference between the EUI and AIA passbands that the discussion invokes when weighing passband effects.","marker":"Chen et al. (2021)"}],"fun_headline_variants":["Solar scopes match on coronal wave damping lengths","Hi-C and AIA see same damping in slow coronal waves","No instrument effect on slow wave damping, dual scopes show","Coronal wave damping not affected by telescope choice"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The comparison stands on the assumption that the 30-minute AIA series with its 5-minute smoothed background and the 5-minute Hi-C series with its flat full-duration background are measuring the same, effectively stationary wave amplitude.","fun_headline_variants_meta":{"raw":{"variants":["Solar scopes match on coronal wave damping lengths","Hi-C and AIA see same damping in slow coronal waves","No instrument effect on slow wave damping, dual scopes show","Coronal wave damping not affected by telescope choice"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000392,"raw_usage":{"total_tokens":2200,"prompt_tokens":1227,"completion_tokens":973,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":843,"completion_tokens_details":{"reasoning_tokens":906}},"tokens_in":843,"tokens_out":973,"duration_ms":8737,"temperature":1.0,"reasoning_tokens":906,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-07T05:59:31.259506+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Re-run the amplitude-tracking analysis using only the AIA data that overlap the Hi-C window, with the same flat background and the same 5-minute series length used for Hi-C: if the resulting $L_d$ leaves the quoted $3.4\\pm1.0$ Mm uncertainty, the cross-instrument agreement depends on series length or background choice; if it stays near 3.7 Mm, the null result holds.","supporting_citations":[{"cited_title":"S., Walsh, R","cited_arxiv_id":null,"evidence_quote":"Provides an earlier same-passband, two-spacecraft measurement whose damping lengths agreed within large uncertainties."},{"cited_title":"P., Reep, J","cited_arxiv_id":null,"evidence_quote":"Supplies the cross-correlation coalignment procedure used to ensure both instruments sample the same loop."}],"review_version":1}