{"id":"1312b351-8cd3-4c94-b25d-7e40e5791546","arxiv_id":"1908.07484","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":4.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":8,"one_line_summary":"Analysis of 2015-2017 HAWC scaler rates identifies 79 thunderstorm-coincident count-rate increases that correlate with the atmospheric electric field.","lead":"Using three years of HAWC scaler data, this paper finds about 100 short increases in count rate that line up with thunderstorm electric fields, and lists 79 events with matching field data. It offers a method for spotting storm-driven particle acceleration in a large air-shower detector, though the physics is not yet quantified.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Unvalidated pressure correction is the load-bearing link: without published coefficients or control intervals, the inverse cross-correlations in Fig. 7 may be artifacts of the correction.","rationale":"The reader's weakest_assumption identified the unpublished pressure correction as a key uncertainty, and I agree. The paper's own text in Section 4.1 gives no way to evaluate the correction, and Section 5 immediately bases the main conclusion on the corrected data. This is the most load-bearing point because the entire empirical case for 'particle acceleration due to the electric field of clouds' depends on the residual rate after pressure subtraction. A concrete test — using known HAWC pressure coefficients or fair-weather controls — would settle whether the correlation is genuine. The paper explicitly defers simulations and inverse analysis, so the current evidence is preliminary; the reader's CONDITIONAL verdict remains appropriate. I therefore recommend no change to the verdict.","tokens_in":101,"tokens_out":2338,"duration_ms":35721,"concrete_test":"Take the 79 events and apply a standard barometric correction with published HAWC coefficients (or derive per-detector pressure coefficients from a year of fair-weather scaler data). Recompute the cross-correlation with the Boltek field and regenerate Fig. 7. Also run the same pipeline on a control sample of fair-weather intervals. If the majority anti-correlation disappears or is reproduced in controls, the claim is not supported.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim in Section 5 — that the 79 events show particle acceleration by cloud electric fields — rests on the pressure correction in Section 4.1 removing barometric modulation from the scaler rates. That correction is described only as a method proposed by K.P. Arun Babu, with no coefficients, formulas, or reference, and no validation against control periods. Since the reported inverse correlation between rate and electric field appears only after this correction, an incomplete or incorrect pressure subtraction could itself produce the anti-correlation seen in Fig. 7. The additional choice in Section 4.2 to fit only negative electric-field values is post hoc and compounds the uncertainty. Until the pressure correction is shown to fully remove barometric effects (e.g., by yielding zero correlation in fair-weather intervals), the cross-correlations do not specifically implicate in-cloud electric fields.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper reports a search for thunderstorm-related increases in the count rates of the HAWC scaler system using data from 2015-2017. The authors apply a three-step selection: self-normalizing each detector to its mean rate, requiring an excess above a threshold defined as 1 + 5σ for at least 5 continuous minutes in at least 30 detectors, then selecting events with duration between 5 and 120 minutes. They find 100 such intervals, of which 79 have matched Boltek EFM-100 electric-field data. For those events the authors apply an unpublished barometric pressure correction, smooth the rates, compute cross-correlations between the average scaled rate and the electric field over time lags of -15 to +15 minutes, and fit a linear relation R(E) = -0.22E + 0.09 using only negative electric-field values. They report that most of the 79 events show an inverse correlation between rate and electric field and interpret this as evidence for particle acceleration by thundercloud electric fields.","tokens_in":5349,"tokens_out":3067,"duration_ms":32821,"significance":"If the central claim is correct, the paper would provide a new, relatively simple method for identifying thunderstorm-correlated count-rate enhancements in HAWC's scaler data and would add to the existing evidence for thunderstorm ground enhancements at high altitude. The use of the scaler multiplicity channels and the cross-correlation with a ground-level electric-field monitor is a reasonable observational strategy, and the authors have made an effort to separate thunderstorm effects from solar and atmospheric modulation by a duration cut. However, the paper does not yet establish the claim quantitatively: the barometric correction is not described in a reproducible way, no significance levels or control periods are provided for the cross-correlations, and the sign-restricted linear fit is not justified. Because these points are directly load-bearing for the Section 5 conclusion, the work is best regarded as a promising method paper whose evidence requires substantial strengthening before it can be taken as a demonstration of particle acceleration.","major_comments":[{"comment":"The pressure correction is not reproducible: the text states only that the method was 'proposed by K.P. Arun Babu' and that data are transformed as percentages using 'pressure coefficients for each multiplicity,' but no coefficients, formulas, or reference are given. The paper's central conclusion in Section 5 depends on the residual rate after this correction being attributable to electric fields, so an incomplete or incorrect barometric correction could produce exactly the inverse correlations shown in Fig. 7. The authors should specify the correction completely and validate it, for example by showing that fair-weather intervals yield near-zero cross-correlation between rate and electric field after correction.","section":"Section 4.1"},{"comment":"No statistical significance is reported for the cross-correlation coefficients, and no control periods are analyzed to show that the correlations exceed chance. With 79 events and a wide scan over time lags from -15 to +15 minutes, some large coefficients are expected by chance alone. The authors should report confidence intervals or p-values for the cross-correlation distribution, compare with shuffled or fair-weather control data, and show the lag distribution of the best fits rather than only a histogram of coefficients.","section":"Section 4.2 and Fig. 7"},{"comment":"The linear fit in Eq. (4.1) is performed only on negative electric-field values, with no stated justification, and the resulting negative slope is used to support the claim of an inverse correlation. This sign restriction is a post hoc data-driven choice; if a two-sided fit over the entire field range gives a different slope or a poor fit, the inference changes. The authors should justify the restriction physically or analyze both signs, and they should report the fit uncertainty and the number of points used.","section":"Section 4.2, Eq. (4.1)"},{"comment":"The analysis relies on two assumptions that are not tested: that the 5-120 minute duration window separates thunderstorm effects from solar and atmospheric modulation, and that the ground-level Boltek EFM-100 reading represents the in-cloud electric field relevant for particle acceleration. The first assumption affects which events enter the sample, and the second affects the physical interpretation. A robustness check varying the duration window and a brief discussion of the known limitations of ground-level field measurements would substantially increase confidence in the conclusions.","section":"Section 3.2.1 and Section 4.2"}],"minor_comments":[{"comment":"The manuscript contains numerous typographical errors, including 'selfnolmalization', 'fuction', 'reperesentation', 'stadistical', 'seconadary', 'Adquisition', 'accelaration', 'elctric', and 'enhacements'. These should be corrected in a careful revision.","section":"Throughout"},{"comment":"The threshold in Eq. (3.2) is written as thi = 1 + 5σi, but the text says an event requires the normalized rate to exceed the threshold for 'at least 5 continuous minutes' and in 'at least 30 detectors.' It should be clarified whether σi is the standard deviation of the normalized rate for detector i or of the average, and whether the 30-detector condition applies to every minute of the event.","section":"Section 3.2, Eq. (3.2)"},{"comment":"The smoothing window is described as a 'moving central average with a window of 5 minutes,' but it is not stated whether this is applied before or after the pressure correction and whether the same smoothing is applied to the electric-field data. This affects the cross-correlation results and should be specified.","section":"Section 4.1"},{"comment":"The panel labels in Figure 6 are confusing: the caption reads 'Up to down ,a)Comparison of the average rate with the electric field intensity.b) Comparison of the average rate with the shifted electric field. c)Cross correlation coefficient as a function of time lag.' The panels should be labeled clearly with (a), (b), (c) and the quantities on both axes should be identified.","section":"Figure 6"},{"comment":"Some entries in the event tables contain sublabels such as 'Jun,30b' and 'May,27,a,b', which presumably distinguish multiple events on the same day. The meaning of these sublabels and the criterion for separating same-day events should be explained in the text or table footnote.","section":"Table 1"}],"recommendation":"major_revision","confidential_remarks":"This manuscript appears to be an ICRC 2019 proceedings contribution, and its length and depth are appropriate for that venue. The main scientific claim, however, is stated more strongly than the evidence supports, and the missing validation of the pressure correction, the absence of control periods, and the lack of significance estimates are exactly the issues that a journal referee would require to be addressed. I recommend a major revision rather than rejection because the underlying idea is sound and the deficiencies are fixable within the scope of the paper."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Colleague,\n\nShort take: this is a legitimate but preliminary conference paper from HAWC. The new content is a three-year, three-multiplicity selection of ~100 scaler rate increases, 79 with matching electric field data, plus cross-correlation results. That is a real extension of the earlier HAWC study [9], and the event selection is transparent enough to reproduce. It deserves a careful referee, but the quantitative claims are not yet supported by the analysis as written.\n\nWhat it does well: the self-normalization and threshold selection are simple and explicitly stated. Requiring a minimum duration and a minimum number of detectors is a sensible guard against PMT glitches. The paper is honest that simulations and an inverse test are still pending. The event list itself could be useful to the atmospheric-electricity community.\n\nWhere it is soft: the pressure correction in Sec. 4.1 is the main problem. It is described only as \"the method proposed by K.P. Arun Babu,\" with no coefficients, no formula, no reference, and no validation on fair-weather periods. Since the anti-correlation in Fig. 7 appears only after this correction, an incomplete correction could produce or distort that correlation. The stress-test note is on target there. Second, no significance levels or error bars are given for the cross-correlation coefficients or the linear fit in Eq. 4.1. The fit uses only negative electric field values, with no stated justification. Third, there are no control intervals—the paper does not show that the correlations exceed what chance would produce. These are not fatal to the existence of the events, but they are fatal to the specific claim that the rate increase scales with field. The central qualitative claim—that HAWC sees thunderstorm-related rate enhancements—is credible and consistent with prior TGE observations, so the paper is not circular.\n\nWho should read it: anyone working on thunderstorm ground enhancements or HAWC scaler data. The catalog and method are a stepping stone; the physics is not settled here. My recommendation: send it to peer review, but make clear that the pressure correction must be fully documented and validated against control periods before the anti-correlation claim can be accepted. As a conference paper it is fine; as a journal submission it would need major revision.","headline":"A genuinely useful but methodologically incomplete HAWC scaler thunderstorm catalog; the pressure correction and absent significance tests keep the quantitative claim preliminary.","tokens_in":5851,"tokens_out":2967,"would_cite":false,"duration_ms":29906,"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":"Thunderstorm electric fields boost HAWC's scaler count rate.","keywords":["HAWC observatory","scaler rate","thunderstorm ground enhancements","relativistic runaway electron avalanche","atmospheric electric field","cross-correlation","water Cherenkov detector","cosmic-ray air showers"],"falsifier":"Run the same threshold search on thunderstorm-free periods after applying the pressure correction: if comparable 5-to-120-minute rate increases appear, the events are not storm-specific. Alternatively, detrend the 79 event-day rates against local barometric pressure and compare that correlation with the electric-field correlation; a pressure correlation as strong as the field correlation would indicate the effect is barometric, not electric.","tokens_in":4961,"feed_emoji":"⚡","tokens_out":7072,"duration_ms":66392,"temperature":0.7,"pith_summary":"The paper claims that roughly 100 count-rate increases in HAWC's scaler system between 2015 and 2017 occurred during thunderstorms, and that 79 events with electric-field data show a strong cross-correlation between the count rate and the field. The authors argue these enhancements are evidence that thundercloud electric fields accelerate secondary particles through the relativistic runaway electron avalanche mechanism. If correct, the HAWC array, built as a gamma-ray observatory, can also serve as a detector of particle acceleration by atmospheric electricity, and the method can be extended to find more such events in all multiplicity channels.","feed_headline":"Cloud electric fields boost HAWC's particle counter","feed_subtitle":"Across 79 thunderstorms, count-rate spikes track the atmospheric field, pointing to electron avalanches.","key_machinery":"The paper invokes the relativistic runaway electron avalanche (RREA) mechanism, in which energetic seed electrons pushed by a strong field overcome drag and generate bremsstrahlung photons and further runaway electrons, as the physical cause. The operational machinery is the HAWC scaler system and a three-filter event selection: self-normalization of each PMT's count rate, a five-standard-deviation threshold requiring 5+ minutes and 30+ detectors, a 5-to-120-minute duration cut, and the requirement of available electric-field data. The correlation analysis then shifts the electric-field time series by -15 to +15 minutes, takes the best cross-correlation coefficient, and fits the rate against the field to show a negative slope.","core_discovery":"After self-normalizing each detector's per-minute scaler rate to its own mean, the authors set a threshold of one plus five standard deviations and require the normalized rate to exceed it for at least five consecutive minutes in at least 30 detectors. That first filter yields 202 candidate intervals; restricting duration to between 5 and 120 minutes leaves 100, and requiring simultaneous electric-field data leaves 79 events. For those 79, a cross-correlation analysis with time shifts from -15 to +15 minutes shows that the majority of events are strongly correlated with the field intensity, and after pressure correction most are inversely correlated: the rate enhancement occurs as the field decays. The paper's stated conclusion is that these results are evidence for particle acceleration due to the electric field of clouds producing enhancements of the HAWC scaler rate.","pith_inferences":["If the ground-level field reading tracks the in-cloud field closely enough, HAWC's scaler system could act as a wide-area, distributed monitor of thunderstorm electrification, complementing lightning-location networks.","The inverse correlation with field intensity suggests the acceleration happens during field collapse rather than at peak field; this timing could be tested by comparing event onsets with lightning-stroke times from a regional array.","Because the pressure correction is unpublished, a natural test is to re-analyze the 79 events with a published barometric coefficient; if the correlations weaken, the method's event list depends on that correction.","The 30-detector minimum may bias the selection toward large, widespread storms, so isolated or small cells producing weaker enhancements would be missed; a single-detector or local-cluster search could find them."],"forward_implications":["HAWC's scaler multiplicities can serve as a thunderstorm detector: rate increases lasting 5 to 120 minutes and coinciding with field changes mark particle acceleration by cloud electric fields.","Because most events show an inverse correlation, the enhancement occurs as the electric field decays, tying the acceleration to the collapse phase of the storm cell.","Applying the same three-filter method to the other multiplicity channels and later years should yield more events, and with simulations may let the energy of the initiating particles be estimated.","The method gives a way to separate true atmospheric-electricity enhancements from solar or barometric modulations, which the two-hour duration cut is designed to exclude."],"supporting_citations":[{"why":"Supplies the original proposal that thundercloud electric fields accelerate charged particles, the basis for interpreting rate increases as atmospheric-electricity effects.","marker":"[1]"},{"why":"Reviews high-energy atmospheric physics and terrestrial gamma-ray flashes, contextualizing particle acceleration by storm fields.","marker":"[3]"},{"why":"Formulates the runaway electron mechanism of air breakdown that underlies the RREA interpretation.","marker":"[4]"},{"why":"Reports earlier ground-level cosmic count increases associated with thunderstorms, motivating the search in HAWC data.","marker":"[5]"},{"why":"Defines thunderstorm ground enhancements as a recognized high-energy phenomenon detected by ground arrays.","marker":"[7]"},{"why":"Provides ground-based observations of thunderstorm-correlated high-energy electron, gamma-ray, and neutron fluxes that the HAWC results extend.","marker":"[8]"},{"why":"Documents HAWC's earlier response to atmospheric electricity activity, the direct precursor for this scaler study.","marker":"[9]"},{"why":"Describes the data acquisition architecture that includes the TDC scaler system used to record PMT hits and multiplicities.","marker":"[11]"},{"why":"Supplies the 30-to-60-minute thunderstorm cell duration used to set the event duration window in the second filter.","marker":"[12]"}],"fun_headline_variants":["Thunderstorm fields spike HAWC scaler rates","HAWC sees electric-field boost in particle counts","Cloud electric fields accelerate particles at HAWC","Scaler rate spikes linked to thunderstorm fields"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The claim rests on the premise that the unpublished pressure correction removes all non-electric weather modulation and that a ground-level field reading represents the in-cloud accelerating field; if either fails, the residual rate increases and their correlations could have a non-electric cause.","fun_headline_variants_meta":{"raw":{"variants":["Thunderstorm fields spike HAWC scaler rates","HAWC sees electric-field boost in particle counts","Cloud electric fields accelerate particles at HAWC","Scaler rate spikes linked to thunderstorm fields"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000626,"raw_usage":{"total_tokens":2892,"prompt_tokens":938,"completion_tokens":1954,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":554,"completion_tokens_details":{"reasoning_tokens":1895}},"tokens_in":554,"tokens_out":1954,"duration_ms":14182,"temperature":1.0,"reasoning_tokens":1895,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-14T12:18:05.913761+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Run the same threshold search on thunderstorm-free periods after applying the pressure correction: if comparable 5-to-120-minute rate increases appear, the events are not storm-specific. Alternatively, detrend the 79 event-day rates against local barometric pressure and compare that correlation with the electric-field correlation; a pressure correlation as strong as the field correlation would indicate the effect is barometric, not electric.","supporting_citations":[{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Supplies the original proposal that thundercloud electric fields accelerate charged particles, the basis for interpreting rate increases as atmospheric-electricity effects."},{"cited_title":"Smith, David and Cummer, Steven, High-Energy Atmospheric Physics: Terrestrial Gamma-Ray Flashes and Related Phenomena,Space Science Reviews,[2012]","cited_arxiv_id":null,"evidence_quote":"Reviews high-energy atmospheric physics and terrestrial gamma-ray flashes, contextualizing particle acceleration by storm fields."},{"cited_title":"and Milikh, G.M","cited_arxiv_id":null,"evidence_quote":"Formulates the runaway electron mechanism of air breakdown that underlies the RREA interpretation."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Reports earlier ground-level cosmic count increases associated with thunderstorms, motivating the search in HAWC data."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Defines thunderstorm ground enhancements as a recognized high-energy phenomenon detected by ground arrays."},{"cited_title":"et al., Ground-based observations of thunderstorm-correlated fluxes of high-energy electrons, gamma rays, and neutrons Phys","cited_arxiv_id":null,"evidence_quote":"Provides ground-based observations of thunderstorm-correlated high-energy electron, gamma-ray, and neutron fluxes that the HAWC results extend."},{"cited_title":"HAWC response to atmospheric electricity activity","cited_arxiv_id":"1711.04202","evidence_quote":"Documents HAWC's earlier response to atmospheric electricity activity, the direct precursor for this scaler study."},{"cited_title":"Abeysekara et al., Data acquisition architecture and online processing system for the HAWC gamma-ray observatory, Nuclear Instruments and Methods in Physics Research A,[2018]","cited_arxiv_id":null,"evidence_quote":"Describes the data acquisition architecture that includes the TDC scaler system used to record PMT hits and multiplicities."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Supplies the 30-to-60-minute thunderstorm cell duration used to set the event duration window in the second filter."}],"review_version":1}