{"id":"c00d51a0-2d2a-4f9b-bb0a-27996143f7eb","arxiv_id":"2506.17917","paper_version":1,"verdict":"CONDITIONAL","confidence":"HIGH","novelty_score":5.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":1,"one_line_summary":"This paper reports the first analysis of the largest Forbush decrease in solar cycle 25, observed on June 1-2, 2025 by the SEVAN network, with two minima and regional anisotropy.","lead":"The SEVAN cosmic ray network tracked a large two-step Forbush decrease on June 1-2, 2025, caused by consecutive Earth-directed coronal mass ejections. The event is presented as the deepest in 20 years, but the supporting comparison to earlier events is missing.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The 'largest in 20 years' claim is not derivable from SEVAN data alone: no comparison to global FD catalogs is provided, and the title/abstract conflict on whether the record is 20 years or just solar cycle 25.","rationale":"The reader's weakest_assumption is exactly the load-bearing issue: the paper asserts a 20-year record without comparing to global neutron-monitor data or prior FD catalogs. My review confirms that the manuscript contains no such comparison, and I additionally note the internal inconsistency between the title ('20 years') and abstract ('solar cycle 25'), which makes the claim's scope ambiguous. The observational FD description is internally coherent, and the two-phase structure is plausibly real, so I do not see a reason to reject the paper; however, the headline claim is unsubstantiated as written. The appropriate resolution is a conditional verdict: either add the missing quantitative comparison or temper the claim to 'largest in solar cycle 25'. Since the reader already reached CONDITIONAL, no verdict change is needed.","tokens_in":4835,"tokens_out":2687,"duration_ms":30956,"concrete_test":"Use the NMDB database to compute the maximum Forbush-decrease amplitude for every event since January 2005 at a standard high-latitude neutron monitor (e.g., Oulu or Apatity), using the same baseline definition as the paper (e.g., mean count rate from 08:00 to 16:00 UT on the day before the storm onset). Also cross-check with published FD catalogs (e.g., Belov et al. or the WDC for Cosmic Rays). If any event in 2005-2025 has an amplitude within or above the 15% Aragats neutron-monitor value after accounting for station cutoff and altitude, the '20 years' claim is not supported. Separately rerun the comparison for solar cycle 25 only (December 2019 onward); if the June 2025 event is indeed the largest in that interval, the paper should align its title and abstract to 'largest in solar cycle 25'.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim appears in the title and Section 2 as 'the largest Forbush decrease in 20 years', while the abstract and introduction say 'largest FD observed in solar cycle 25'. These are different claims: solar cycle 25 began in December 2019, so a 20-year record requires excluding larger events in 2005-2019, not merely within the current cycle. The paper's evidence consists only of SEVAN-measured amplitudes: 7.5-8.8% for upper scintillators, 12% for Mileshovka neutrons, and 15% for the Aragats neutron monitor. Without a quantitative comparison to prior events measured on comparable instruments or taken from a global neutron-monitor FD catalog, a 15% high-altitude neutron-monitor depletion does not establish a 20-year record. This is a missing control on the headline statement, not a matter of consensus: if any event in the past two decades reached or exceeded the same amplitude, the central claim fails. The manuscript itself flags the ambiguity by using 'solar cycle 25' in the abstract and '20 years' in the title, so the claim's scope is not consistently defined.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper reports observations of a Forbush decrease (FD) on 1–2 June 2025 made with the SEVAN particle-detector network, attributing the event to two consecutive Earth-directed CMEs on 30–31 May. It describes two distinct FD minima, amplitude estimates between 7.5% and 15% depending on detector and location, a prolonged recovery, and a claimed European–Aragats anisotropy. The analysis is explicitly preliminary and is based on count-rate depletions relative to an 8-hour baseline on 31 May 2025.","tokens_in":5186,"tokens_out":3248,"duration_ms":34947,"significance":"If the central claim were properly supported, the event would be of substantial interest: a two-step FD with depth exceeding typical solar-cycle events, observed simultaneously by neutron and muon channels at multiple mountain altitudes, could provide valuable spectral and anisotropic information about a complex ICME event. The SEVAN network is a unique instrument with concurrent neutron, muon, and electron/gamma detection, and the paper highlights its diagnostic potential. However, the current manuscript does not yet establish the record claim, and the quantitative analysis lacks the corrections and comparisons needed for a robust scientific conclusion.","major_comments":[{"comment":"The central claim is stated inconsistently and is not supported by quantitative comparison with prior events. The title and Section 2 state 'the largest Forbush decrease in 20 years' (and 'deepest Forbush Decrease in 20 years'), while the Abstract and Introduction state 'largest FD observed in solar cycle 25'. These are different claims: solar cycle 25 began in December 2019, so a 20-year record requires excluding larger events from 2005–2019 (e.g., 2005 January, 2006 December, 2015 June, 2017 September). No comparison to global neutron-monitor data or to a published FD catalog is provided anywhere in the manuscript. If a comparable or larger event occurred within the last 20 years, the headline claim fails. The authors should either supply a quantitative comparison to prior FDs (e.g., using Neutron Monitor Database data) or restrict the claim to solar cycle 25 consistently across title, abstract, and text.","section":"Title and Abstract"},{"comment":"The reported depletion percentages (7.5–8.8% for upper scintillators, 12% for Mileshovka neutrons, 15% for ArNM) are given without any uncertainty estimates or corrections. In particular, no barometric pressure correction is described for the neutron monitors, which is essential for isolating the cosmic-ray modulation from atmospheric effects; the 8-hour baseline window (May 31, 08:00–16:00) is short and may include diurnal variations or transient increases, and no statistical error bars are shown in the figures. Without these, differences of ~1% between stations (e.g., 7.9% vs. 8.8%) cannot be interpreted as physically significant. Please add error bars (statistical, and where applicable systematic, from pressure/efficiency) and describe or justify the baseline normalization.","section":"Section 3, Figures 1–4"},{"comment":"The claimed anisotropy between European and Aragats detectors is not convincingly established. The detectors are at different altitudes (Aragats 2000/3200 m, Lomnicky Stit 2634 m, Musala 2930 m, Mileshovka 837 m) and different geomagnetic cutoffs. The observed differences in depletion depth could be largely due to atmospheric attenuation and rigidity cutoff differences, not to a spatial anisotropy of the cosmic-ray flux. The paper itself notes that NANM at 2000 m shows a 2% smaller depletion than ArNM at 3200 m, which is consistent with an altitude effect. To support the anisotropy claim, the authors should compare detectors at similar atmospheric depth or use a transport/response model to quantify the expected altitude and cutoff dependence.","section":"Section 3, European–Aragats anisotropy"},{"comment":"The association of the first FD phase with the 'cannibal' ICME and the second phase with the May 31 CME is plausible but is not quantitatively demonstrated from the in-situ data. The text lists SSC times and Btotal jumps, but does not show time profiles of the solar-wind speed, IMF Bz, or plasma density for the 31 May–3 June interval. To support the two-phase interpretation, the authors should present these interplanetary parameters alongside the cosmic-ray time series so that the shock arrivals and the ICME structures are visible rather than asserted.","section":"Section 2, Figure 1"}],"minor_comments":[{"comment":"The caption is incomplete: it reads 'mean values from 8:00 to ' and then the time '16:00' appears on the next line; please fix the formatting so the full interval is stated in one place.","section":"Figure 1 caption"},{"comment":"The paper cites Karapetyan et al. (2024) on a Forbush decrease observed by SEVAN in the 25th cycle, but does not compare the current event with that earlier event. A brief quantitative comparison would help support the 'largest in cycle 25' claim.","section":"References and prior work"},{"comment":"The terms 'largest Forbush decrease' and 'deepest Forbush Decrease' are used interchangeably; consider using one consistent descriptor (e.g., 'largest amplitude' or 'deepest minimum').","section":"Terminology"}],"recommendation":"major_revision","confidential_remarks":"The manuscript would likely be suitable as a research letter after the record claim is corrected or substantiated, and after basic uncertainty/correction information is added. The main risk is that the headline claim is contradicted by prior events; a check against the NMDB or a published FD catalog would resolve this. The paper's short length and preliminary nature do not excuse the inconsistency between the title and the abstract, which should be addressed in revision."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"You should know two things about this paper. First, the underlying observation—a two-phase Forbush decrease seen across the SEVAN network on June 1–2, 2025, with a clear European–Aragats anisotropy—is credible and worth having on the record. Second, the title and the abstract are arguing with each other, and the stronger claim is not supported.\n\nWhat's actually new: this is the first report of this specific event using the SEVAN network, and the two-minima structure tied to the successive CME shocks is a legitimate new measurement. The network has been running for nearly two decades, so the raw count rates are probably as trustworthy as any in the field. The paper also does a decent job connecting the SSC timings to the two FD phases, and the qualitative distinction between neutron and muon response is plausible and internally consistent.\n\nThe soft spots are real but mostly about framing rather than the core data. The title says \"largest Forbush decrease in 20 years,\" while the abstract says \"largest in solar cycle 25.\" Those are different claims—cycle 25 started in December 2019, so a 20-year record would require showing that nothing in 2005–2019 was deeper. No such comparison is attempted. The paper relies only on SEVAN amplitudes (7.5–8.8% for upper scintillators, 12% for Mileshovka neutrons, 15% for Aragats neutron monitor), and a 15% high-altitude neutron monitor depletion does not by itself establish a 20-year record without reference to global neutron monitor data or an FD catalog. There are also no error bars, no pressure/efficiency corrections described, and the baseline is a short 8-hour window on May 31 that may already be contaminated by the approaching CME. These are minor if the paper is read as a preliminary data release, but they matter because the headline claim depends on exactly that missing context.\n\nWho is this for? Space weather specialists and cosmic ray modulation people who want a quick look at the June 2025 event. It is not a deep analysis, but it is a useful first report. The event is important enough that a serious referee should engage with it, and the paper can be fixed by making the record claim match the evidence—either add a quantitative comparison to prior events or temper the title and abstract to \"largest in solar cycle 25\" or \"among the largest in recent decades.\" I would send it to peer review with that request, and also ask for error bars and a longer, better-justified baseline.\n\nRecommendation: engage it, but make the authors earn the superlative.","headline":"Useful first look at the June 2025 Forbush decrease from SEVAN, but the 'largest in 20 years' claim is not backed by the evidence presented.","tokens_in":5593,"tokens_out":2221,"would_cite":true,"duration_ms":26394,"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":"The SEVAN network observed the deepest Forbush decrease in 20 years, triggered by back-to-back Earth-directed coronal mass ejections on May 30-31, 2025, with two distinct minima and a week-long recovery.","keywords":["Forbush decrease","SEVAN network","cosmic rays","coronal mass ejection","solar cycle 25","neutron monitor","muon detector","space weather"],"falsifier":"Searching hourly count-rate records from the worldwide neutron-monitor network for 2005-2025 and finding a Forbush decrease with a deeper minimum than the roughly 15% depletion seen at Aragats, or with two comparable minima at similar rigidity, would falsify the 'largest in 20 years' claim.","tokens_in":4639,"feed_emoji":"☀️","tokens_out":8576,"duration_ms":84080,"temperature":0.7,"pith_summary":"The paper reports the deepest Forbush decrease in two decades as seen by the SEVAN network, a set of mountain-top particle detectors in Armenia and Europe. It claims the event was triggered by two consecutive Earth-directed coronal mass ejections on May 30 and 31, 2025, whose interplanetary shocks arrived at Earth on June 1 and June 2 and produced two distinct minima in cosmic-ray flux. A prolonged recovery lasting nearly a week and a clear European-Aragats anisotropy are presented as evidence of the compound, structured nature of the interplanetary disturbance. If the record claim holds, the event becomes a benchmark for solar cycle 25 and a test case for how energy-differentiated muon and neutron measurements disentangle heliospheric modulation from magnetospheric effects.","feed_headline":"SEVAN sees deepest cosmic-ray dip in 20 years","feed_subtitle":"Back-to-back solar eruptions on May 30-31, 2025 produced two Forbush-decrease minima and a week-long recovery.","key_machinery":"The central object is the SEVAN network, the Space Environment Viewing and Analysis Network, a chain of hybrid particle detectors at mountain altitudes in Armenia and Europe that records neutrons and muons, together with the STAND3 stacked detector that separates muons by energy threshold and the Aragats and Nor Amberd neutron monitors. The argument works by comparing energy-differentiated responses: neutrons originating from roughly 1-20 GeV primaries show the strongest Forbush-decrease signal because that is where heliospheric modulation is strongest, while muons with higher-energy primaries respond to both heliospheric modulation and local geomagnetic cutoff changes. This energy ladder lets the authors attribute the two FD minima to the two interplanetary shocks and attribute the European-Aragats asymmetry to a spatial anisotropy in the cosmic-ray depression. The mechanism also separates genuine FD signals from thunderstorm ground enhancements, which appear as short bursts in low-threshold detectors.","core_discovery":"The authors claim that a compound interplanetary coronal mass ejection, formed when the fast May 31 CME overtook the earlier May 30 CMEs, produced the largest Forbush decrease in 20 years. The first shock, detected at 05:22 UTC on June 1, initiated the first FD phase with a roughly 7.5% depletion at all SEVAN locations around 15:00 UTC on June 1. The second shock, detected at 10:19 UTC on June 2, deepened the decrease unevenly: European detectors reached 7.9% at Lomnicky Stit and 8.8% at Musala around 17:40 UTC, while Aragats showed a shallower minimum. Neutron-selected channels showed larger depletions, 12% at Mileshovka and 15% at the Aragats neutron monitor, with Nor Amberd 2% smaller due to atmospheric cutoff, and muon channels displayed a 12% depletion at a 40 MeV threshold versus 8% at 300-400 MeV thresholds. The differing amplitudes are interpreted as signatures of both global heliospheric modulation and local geomagnetic cutoff variations, with recovery taking nearly a week.","pith_inferences":["A quantitative comparison with global neutron-monitor archives from 2005-2025 would either confirm the record claim or locate a comparable or deeper event, sharpening the claimed time window.","The European-Aragats anisotropy implies a spatial gradient in the cosmic-ray depression across roughly 2,000 km; modeling the compound ICME's magnetic structure could predict the gradient's sign and magnitude.","The muon spikes superimposed on the FD trend suggest that geomagnetic cutoff changes during storms contaminate low-energy muon records, so revisiting archival SEVAN data from earlier storms could reveal similar magnetospheric effects in past events."],"forward_implications":["If the record claim is correct, the June 1-2, 2025 event becomes the reference Forbush decrease of solar cycle 25, against which future events will be compared.","Energy-differentiated muon channels would become a standard tool for separating heliospheric modulation from magnetospheric effects in real time, improving space-weather nowcasting.","The two-step structure and week-long recovery imply that forecasts must treat merging CMEs as compound disturbances rather than isolated shocks.","The observed European-Aragats anisotropy indicates that single-station measurements underestimate or miss the full depth of strong Forbush decreases, supporting the continued operation of distributed networks.","Intercalibration of SEVAN detectors with neutron monitors at the same sites provides a way to translate SEVAN depletion percentages into neutron-monitor-equivalent amplitudes for comparison with historical records."],"supporting_citations":[{"why":"Describes the SEVAN network's design and initial installations, the instrument that produced the reported observations.","marker":"Chilingarian et al., 2009"},{"why":"Documents ten years of SEVAN operation, establishing the network's reliability for detecting solar-cycle variations.","marker":"Chilingarian et al., 2018"},{"why":"Supplies the method for interpreting ICME-driven changes in terrestrial particle fluxes, used to classify the June 2025 event.","marker":"Chilingarian et al., 2024c"},{"why":"Defines the STAND3 stacked-detector coincidence technique that separates muons by threshold energy, central to distinguishing heliospheric from magnetospheric effects.","marker":"Chilingarian and Hovsepyan, 2023"},{"why":"Shows how muon detectors with different energy thresholds classify solar events, supporting the energy-differentiation interpretation.","marker":"Chilingarian et al., 2024b"},{"why":"Defines the Forbush decrease phenomenon that the paper claims to observe at record depth.","marker":"Forbush, 1950"}],"fun_headline_variants":["Back-to-back CMEs cause largest cosmic-ray dip in 20 years","Largest Forbush decrease in 20 years: double CME shockwave","Double solar eruption causes biggest cosmic-ray dip in 20 years","Two shock waves from solar storms trigger deepest cosmic-ray dip in 20 years"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The record claim depends on SEVAN's own measurements being sufficient to establish that no larger Forbush decrease occurred in the past 20 years, without a quantitative comparison to global neutron-monitor records.","fun_headline_variants_meta":{"raw":{"variants":["Back-to-back CMEs cause largest cosmic-ray dip in 20 years","Largest Forbush decrease in 20 years: double CME shockwave","Double solar eruption causes biggest cosmic-ray dip in 20 years","Two shock waves from solar storms trigger deepest cosmic-ray dip in 20 years"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000748,"raw_usage":{"total_tokens":3324,"prompt_tokens":927,"completion_tokens":2397,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":543,"completion_tokens_details":{"reasoning_tokens":2320}},"tokens_in":543,"tokens_out":2397,"duration_ms":18405,"temperature":1.0,"reasoning_tokens":2320,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-06T23:22:03.716016+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Searching hourly count-rate records from the worldwide neutron-monitor network for 2005-2025 and finding a Forbush decrease with a deeper minimum than the roughly 15% depletion seen at Aragats, or with two comparable minima at similar rigidity, would falsify the 'largest in 20 years' claim.","supporting_citations":[],"review_version":1}