{"id":"ffb613e5-eb35-4e76-af11-d99987e77154","arxiv_id":"2507.21373","paper_version":1,"verdict":"CONDITIONAL","confidence":"HIGH","novelty_score":3.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":0,"one_line_summary":"A small scintillator array at 2280 m in Mexico City is being commissioned to study how storms and solar events change the rate of secondary particles from cosmic-ray air showers.","lead":"Physicists at UNAM in Mexico City are building a rooftop cosmic-ray detector to study how storms and solar events change the flow of secondary particles from cosmic rays. The project is still being commissioned, but it has already seen a known space-weather effect and recorded hints of lightning-related rate changes.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The claimed CME detection is not separated from barometric pressure: with only daily bins and no pressure correction, a multi-day weather system could produce the same ~8% rate decrease.","rationale":"The reader's weakest_assumption is precisely the pressure-correction confound in the CME attribution. My independent reading of Sections 4 and 5 reaches the same conclusion: the absence of pressure correction, combined with daily binning, leaves a plausible local-weather alternative to the claimed CME effect. This does not move the verdict because the reader's verdict was already CONDITIONAL and this is the same condition that motivated it. The paper's other claims are transparently hedged as commissioning results, so no additional reason for rejection or stronger revision emerges.","tokens_in":712,"tokens_out":751,"duration_ms":69043,"concrete_test":"Retrieve the local Davis Vantage Pro2 pressure data for May 25-June 8, 2025, and compute the barometric coefficient for these detectors (e.g., by regressing hourly rate against pressure during a quiescent period). Apply the pressure correction to the hourly rates and rebin to daily values. If the week-long decrease survives with a magnitude consistent with the Forbush decrease reported by the UNAM observatory (using its pressure-corrected data), the CME attribution is supported. If the corrected decrease shrinks to a few percent or disappears, the central claim would need to be revised.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The paper's central quantitative result—an ~8% decrease in secondary-particle rate attributed to the May 2025 CME (Section 4, Figure 5)—is not corrected for atmospheric pressure. The text states: 'we are not ready to perform pressure corrections on the data. Instead, we show the data using daily bins.' Daily binning removes only the diurnal cycle, not multi-day pressure trends. At 2280 m a.s.l., a synoptic-scale pressure rise of a few tens of hPa can alter the secondary muon rate by several percent, which is comparable to the claimed 8% decrease. The two subarrays being in different locations (office vs. rooftop) does not rule out a common local pressure system. The comparison with the Mexico City Cosmic Ray Observatory's ~12% decrease is suggestive, but the paper gives no details on that instrument's analysis, pressure correction, or simultaneity, so it cannot be used to exclude a common local atmospheric cause. Because the CME observation is the main evidence that the small detector array can resolve geophysical-scale variations, this unaddressed confound is load-bearing for the central claim.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper reports on the status and first results of the Piritakua project, a small array of CosmicWatch plastic scintillators at UNAM in Mexico City (2280 m a.s.l.), operated alongside a weather station, an electric-field mill, a magnetometer, and an all-sky camera. The stated goal is to study transient atmospheric effects on secondary cosmic-ray particles. The main preliminary result is a reported ~8% decrease in the secondary-particle count rate during the late-May/early-June 2025 coronal mass ejection (CME), observed independently in two subarrays (office and rooftop), and compared with a ~12% decrease reported by the Mexico City Cosmic Ray Observatory. The paper also shows a thunderstorm example with electric-field and rate measurements, interpreted only as hints of a possible correlation. The authors acknowledge that pressure corrections are not yet applied and that the lightning-rate correlation requires more data.","tokens_in":5606,"tokens_out":3531,"duration_ms":44815,"significance":"If the CME attribution is correct, the paper demonstrates that a small, low-cost, open-source detector array can resolve geophysical-scale transient variations in secondary cosmic-ray intensity, which would be a useful proof of principle for broader deployments. The simultaneous use of meteorological and electromagnetic sensors is a good design, and the two independent subarrays plus the external comparison are positive features. The manuscript is honestly hedged about the thunderstorm result, and the detector development is described in useful detail. However, the central quantitative claim—the ~8% CME-related decrease—is not yet separated from atmospheric pressure effects, which is the main load-bearing weakness.","major_comments":[{"comment":"The attribution of the observed ~8% rate decrease to the CME is not separated from barometric pressure effects. The text explicitly states: 'we are not ready to perform pressure corrections on the data. Instead, we show the data using daily bins.' Daily binning removes the diurnal cycle but not multi-day synoptic pressure trends; at 2280 m a.s.l., pressure changes of a few tens of hPa can alter the secondary muon rate by several percent, comparable to the claimed signal. Please quantify the atmospheric pressure variation over the full period (using the Davis station or external pressure records), overlay the pressure time series on Figure 5, and either perform a pressure correction or demonstrate quantitatively that the rate decrease is not anticorrelated with local pressure. This is necessary to support the central claim in the Summary.","section":"Section 4, Figure 5"},{"comment":"The comparison with the Mexico City Cosmic Ray Observatory's ~12% decrease is too underspecified to serve as evidence against a local atmospheric cause. The manuscript gives no information on that instrument's detector type, energy threshold, altitude, pressure-correction procedure, or the exact time window of the quoted decrease. Without those details, the reader cannot tell whether the two measurements probe the same physical quantity or whether a common local weather system could affect both. Please either provide those details, cite a public data release with a documented analysis, or downgrade the comparison to a qualitative consistency check.","section":"Section 4, comparison with Mexico City Cosmic Ray Observatory"},{"comment":"The magnitude of the decrease ('of the order of ~8%') is not defined with respect to a baseline, and no statistical uncertainties are shown on the daily rate points. Please state how the baseline rate was computed (for example, an average over a quiet epoch before the CME), report the statistical error on each rate measurement, and evaluate the significance of the deficit in each subarray separately. As written, the reader cannot judge whether the structure is significant or quantify the confidence of the CME claim.","section":"Section 4, Figure 5"},{"comment":"The lightning-correlation result is presented only as 'hints' and the text says more data are needed, which is appropriately cautious. However, if the figure is to support even a hint, it should be accompanied by a quantitative measure—for example, a correlation coefficient, a binned significance, or a comparison of rate fluctuations before/after the lightning trigger. As it stands, the claim is purely qualitative, and the lack of error bars on the one-second rates makes the visual impression unreliable. Please either add a simple statistical characterization or explicitly mark the figure as an illustration of data quality rather than evidence.","section":"Section 4, Figure 9"}],"minor_comments":[{"comment":"Several reference entries are incomplete and inconsistent with standard journal citations: [1] gives 'Nature 2024 53–56' without volume/article number; [2] gives 'Physical Review D2025063023' without volume/page; [4] gives 'JINST 2018P03019' without volume; [10] and [11] are missing journal volume/page details. Please check all bibliographic entries against the publisher's final versions.","section":"References"},{"comment":"The caption says 'The two markers indicate data from two different testing arrays,' but it is not clear which marker corresponds to the office subarray and which to the rooftop subarray. Please identify the subarrays explicitly in the caption or with a legend.","section":"Section 4, Figure 5"},{"comment":"The sentence 'All of these prototypes have a smaller surface than the design goal size of 20 cm per side' is vague; please state the actual sensitive area of the prototypes used for the CME measurement, since the absolute rate and its sensitivity to pressure depend on the detector size.","section":"Section 2"},{"comment":"There are several minor grammatical and punctuation issues, including run-on sentences (for example, 'It is interesting to notice that there seem to be hints of structures in the detection rate, that possibly correlate...' should be '...in the detection rate that possibly correlate...') and inconsistent spacing between words in the proceedings format. A careful proofread is recommended.","section":"General"}],"recommendation":"major_revision","confidential_remarks":"This is a proceedings-style status report for ICRC 2025, so the bar for quantitative rigor is lower than for a full journal article. Still, the Summary's central claim that the CME was 'observed' is the main result, and the manuscript itself acknowledges the missing pressure correction. I believe the claim is likely correct, but the paper should either add a pressure analysis or rephrase the claim as a candidate observation pending pressure correction. The scope of the journal/proceedings (high-energy physics instrumentation and atmospheric effects) is appropriate, and the paper will be acceptable after the pressure issue is addressed. I do not see any circularity or invented-entities concerns."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Quick take: this is a conference-proceeding status report, not a physics result. The detector repackages CosmicWatch electronics with larger scintillators and a few environmental monitors, and the paper is transparent that it is early days. The one quantitative observation—an ~8% rate dip during a May 2025 CME—is consistent with a Forbush decrease and is supported by two independent subarrays plus an external observatory. That is credit-worthy. But the dip is not corrected for atmospheric pressure; the paper openly says so, and daily binning only removes the diurnal cycle, not multi-day weather. At 2280 m, a passing synoptic system could shift the muon rate by several percent, which is the same order as the claimed effect. So the central quantitative claim does not nail the cause, even though the authors are careful to call it preliminary. The lightning correlation is a single-event anecdote; they label it 'hints,' which is exactly the right level.\n\nWhat's genuinely useful here is the engineering: the larger scintillator with wavelength-shifting fibers, the 3D-printed mounts, and the integration of weather, electric-field, and magnetometer data around a CosmicWatch core. Others building small arrays may find the assembly details worth copying. The comparison with the Mexico City Cosmic Ray Observatory is a nice external sanity check, though without details on that instrument's analysis it is only suggestive. No data or code are released, which is a shame for a paper whose main value is reproducible setup.\n\nFor a journal, this needs pressure corrections, error bars, and a proper statistical treatment of the lightning correlation. As a conference proceeding, it's fine. I'd happily referee it as a detector note; I'd caution an editor not to treat the CME observation as a confirmed measurement. If this were submitted to a full journal, I'd expect heavy revision, but the honest reporting and useful construction details make it worth referee time. I would not cite it as evidence for Forbush decreases, but I might cite it as an example of an inexpensive high-altitude array.","headline":"Honest, modest commissioning report from a small Mexico City array; the CME rate decrease is plausible but not separated from barometric effects, so it reads as a status update rather than a measurement.","tokens_in":6167,"tokens_out":2863,"would_cite":false,"duration_ms":35334,"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":"Piritakua aims to show that a small rooftop scintillator array can read geophysical and thunderstorm effects in the secondary cosmic-ray rate, with an 8% CME dip as first evidence.","keywords":["cosmic-ray secondary particles","scintillator detector array","coronal mass ejection","atmospheric electric fields","thunderstorm ground enhancements","Forbush decrease","high-altitude detection site","air showers"],"falsifier":"Run the same May-June 2025 data through a standard barometric correction using the co-located weather station's pressure record, and check whether the roughly 8% dip remains centered on the CME arrival and recovers over a week; if it disappears or tracks a local pressure front instead, the geophysical attribution collapses.","tokens_in":5278,"feed_emoji":"⚡","tokens_out":8538,"duration_ms":103530,"temperature":0.7,"pith_summary":"The paper is a status report for Piritakua, a compact cosmic-ray detector in Mexico City at 2280 m above sea level, built from scintillator modules and an array of environmental sensors. Its working hypothesis is that transient atmospheric conditions—pressure, temperature, humidity, and the local electric and magnetic fields—modify how air-shower secondaries are produced and propagate, and that a small detector array can resolve those modulations. The first result supporting this hypothesis is an approximately 8% decrease in measured particle rate during the CME that passed Earth in late May and early June 2025, followed by a recovery over roughly a week, observed simultaneously in two independent detector sets. The paper also reports tentative rate variations during a June 11 thunderstorm that may line up with electric-field changes near a lightning discharge, while cautioning that confirmation requires more data.","feed_headline":"Small cosmic-ray array tracks a solar storm's 8% dip","feed_subtitle":"Two independent detector sets saw the CME's week-long rate drop, and thunderstorm hints are in view.","key_machinery":"The mechanistic core is the paired particle and environment measurement: plastic scintillator tiles, enlarged from 25 $cm^{2}$ to 400 $cm^{2}$ by wavelength-shifting fibers coupled to silicon photomultipliers (SiPMs), are read out by compact Arduino-based electronics, while an electric-field mill, a magnetometer, a weather station, and an all-sky camera record the surrounding atmospheric state. This synchronization is what lets the authors compare a particle-rate change with the CME's geomagnetic signature and with lightning-triggered field changes. The physics being exploited is the interaction of secondary cosmic rays with atmospheric column density and electric fields: pressure changes alter absorption and lateral spread, and electric fields accelerate or deflect charged secondaries. The two detector subarrays used different thresholds and exposure conditions, so they are kept separate; their agreement is the main cross-check behind the CME attribution.","core_discovery":"The central claim, stated by the authors in the summary, is that even though Piritakua is a small-scale experiment, it has observed the effect of a CME in the measured particle rate and hints of the effect of thunderstorm electric fields on secondary particle propagation. The CME signal appears as a maximum rate decrease of about 8% in both detector subarrays, with the local magnetometer trace matching the shape of the reported geomagnetic storm, and a larger nearby observatory saw about 12%. The thunderstorm observation is explicitly a hint: one-second binned rates during the June 11 storm show possible structures that correlate with electric-field variations produced by lightning, but the authors say more data are needed. In its own framing, the paper establishes that the Piritakua array can serve as a sensitive, multi-sensor probe of high-energy atmospheric physics.","pith_inferences":["The paper's own caveat about missing pressure corrections suggests a direct test: comparing the daily-binned rate against the co-located weather station's pressure record for May 25 through June 8 would show whether the 8% dip is geophysical or meteorological.","Because the critical field for relativistic runaway electron avalanches is about 24% smaller at Mexico City's altitude than at sea level, the same array might be a more sensitive site for thunderstorm-electric-field effects than a sea-level detector of equal area.","The magnetometer gap during the June 11 storm leaves the thunderstorm hint uncheckable against magnetic data; keeping all sensors running through storms would let a future analysis separate electric-field-driven rate changes from purely meteorological ones.","A similar detector at a site with frequent and intense thunderstorms could test whether the hinted rate structures scale with local electric-field strength or with detector area."],"forward_implications":["A pressure-corrected version of the CME time series would let the collaboration compare its 8% dip quantitatively with the roughly 12% seen by the larger nearby observatory.","The planned 16-module array would increase collecting area enough to target minute-long thunderstorm ground enhancements (TGEs) that the current prototype setup can only hint at.","If the CME signal holds up, small and inexpensive urban scintillator arrays become plausible building blocks for a distributed space-weather and atmospheric-electric-field monitoring network.","The co-located electric-field mill, magnetometer, weather station, and all-sky camera make the same detector array a candidate platform for studying gamma-ray glows and related high-energy atmospheric phenomena."],"supporting_citations":[{"why":"Provides the detector hardware design whose Arduino/SiPM readout the Piritakua modules adapt.","marker":"[4]"},{"why":"Supplies the physics and operating background for the desktop muon detector electronics used in the array.","marker":"[3]"},{"why":"Documents the roughly 10 ms serial-port timing uncertainty that defines the detector's time resolution.","marker":"[5]"},{"why":"Models the effect of near-Earth thunderstorm electric fields on cosmic-ray air-shower flux and justifies the altitude argument for Mexico City.","marker":"[2]"},{"why":"Reviews terrestrial gamma-ray flashes and related high-energy atmospheric phenomena, giving the scientific framework for the proposed measurements.","marker":"[10]"},{"why":"Catalogs gamma-ray glows and serves as the methodological template for observing thunderstorm ground enhancements.","marker":"[11]"},{"why":"Introduces flickering gamma-ray flashes, the radio- and optically-silent phenomenon motivating the project's thunderstorm campaign.","marker":"[1]"}],"fun_headline_variants":["Cosmic-ray array records 8% CME rate drop","Small cosmic-ray lab sees solar storm's 8% dip","Piritakua detector observes 8% CME decrease","Tiny array, big storm: 8% dip from CME","Atmospheric lab spots solar storm in cosmic rays"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The central claim assumes that the observed roughly 8% rate decrease tracks the CME rather than a local weather system, because the paper's shown analysis applies no pressure correction and bins the rate by day.","fun_headline_variants_meta":{"raw":{"variants":["Cosmic-ray array records 8% CME rate drop","Small cosmic-ray lab sees solar storm's 8% dip","Piritakua detector observes 8% CME decrease","Tiny array, big storm: 8% dip from CME","Atmospheric lab spots solar storm in cosmic rays"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000263,"raw_usage":{"total_tokens":1571,"prompt_tokens":888,"completion_tokens":683,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":504,"completion_tokens_details":{"reasoning_tokens":598}},"tokens_in":504,"tokens_out":683,"duration_ms":8258,"temperature":1.0,"reasoning_tokens":598,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-06T12:49:05.790338+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Run the same May-June 2025 data through a standard barometric correction using the co-located weather station's pressure record, and check whether the roughly 8% dip remains centered on the CME arrival and recovers over a week; if it disappears or tracks a local pressure front instead, the geophysical attribution collapses.","supporting_citations":[{"cited_title":"Axani, K","cited_arxiv_id":null,"evidence_quote":"Provides the detector hardware design whose Arduino/SiPM readout the Piritakua modules adapt."},{"cited_title":"The Physics Behind the CosmicWatch Desktop Muon Detectors","cited_arxiv_id":"1908.00146","evidence_quote":"Supplies the physics and operating background for the desktop muon detector electronics used in the array."},{"cited_title":"Axani, K","cited_arxiv_id":null,"evidence_quote":"Documents the roughly 10 ms serial-port timing uncertainty that defines the detector's time resolution."},{"cited_title":"Effect of near-earth thunderstorm electric field on the flux of cosmic ray air showers in LHAASO-KM2A","cited_arxiv_id":"2410.07925","evidence_quote":"Models the effect of near-Earth thunderstorm electric fields on cosmic-ray air-shower flux and justifies the altitude argument for Mexico City."},{"cited_title":"& Cummer, S.A.High-Energy Atmospheric Physics: Terrestrial Gamma-Ray Flashes and Related Phenomena, Space Sci Rev2012 173, 133-196","cited_arxiv_id":null,"evidence_quote":"Reviews terrestrial gamma-ray flashes and related high-energy atmospheric phenomena, giving the scientific framework for the proposed measurements."},{"cited_title":"Catalog of Gamma-ray Glows during Four Winter Seasons in Japan","cited_arxiv_id":"2108.01829","evidence_quote":"Catalogs gamma-ray glows and serves as the methodological template for observing thunderstorm ground enhancements."},{"cited_title":"et al.,Flickering gamma-ray flashes, the missing link between gamma glows and TGFs,Nature 2024 53–56","cited_arxiv_id":null,"evidence_quote":"Introduces flickering gamma-ray flashes, the radio- and optically-silent phenomenon motivating the project's thunderstorm campaign."}],"review_version":1}