[論文レビュー] Atmospheric effects on cosmic-ray muon rate at high latitude (78.9°N)

M. Abbrescia, C. Avanzini+72 more|arXiv (Cornell University)|Mar 4, 2026

Astrophysics and Cosmic Phenomena被引用数 0

ひとこと要約

The paper analyzes six years of POLA-R muon data at Ny-Ålesund (78.9°N) to quantify how atmospheric temperature profiles affect ground-level muon rates, proposing a latitude-aware temperature-weighted correction method and comparing it with traditional approaches.

ABSTRACT

Since 2019, three scintillator detectors of the EEE collaboration have been continuously measuring cosmic muon rates at 78.9°N at the Ny-Ålesund Research Station (Svalbard). The resulting six-year time series reveals a pronounced annual modulation, driven primarily by seasonal atmospheric variations. Utilizing routine radiosonde profiles collected above the same site, we applied several established techniques --along with a tailored analysis approach-- to investigate the relationship between muon rate and atmospheric temperature. The temperature-corrected muon-rates are analysed using the Lomb-Scargle periodogram technique in order to investigate the presence of remaining periodic structures. Finally, the temperature corrections coefficients of our analysis are compared with measurements in other stations located at lower latitudes.

研究の動機と目的

• Quantify the impact of atmospheric temperature on muon rates at high latitude (Ny-Ålesund, 78.9°N) after barometric correction.
• Evaluate multiple temperature-based correction models (linear and integral) using radiosonde-derived profiles.
• Develop a latitude-aware temperature correction approach (DCM) and compare with existing methods.
• Assess residual periodicities after temperature correction and compare POLA-R results with neutron data and lower-latitude measurements.

提案手法

• Correct muon rates for atmospheric pressure using a per-detector barometric coefficient.
• Apply several temperature correction models: ATE (isobar 100 hPa altitude), MMP (temperature at 16.5 km), MSS (mass-weighted temperature profile), DCM (Pearson-correlation-based layer weighting).
• Compute short-term variations: ΔI_PC^{STV} = 100*(I_PC(t) − I_roll(t))/I_roll(t).
• Derive temperature coefficients α via linear regressions between ΔI_PC^{STV} and ΔT parameters (ΔH_100hPa, ΔT at MMP, ΔT weighted by MSS, ΔT from DCM).
• Use Lomb–Scargle periodograms on temperature-corrected data to search for residual periodicities.
• Compare α-values and Pearson correlations with GMDN results at lower latitudes to assess latitude dependence.

実験結果

リサーチクエスチョン

• RQ1 How does atmospheric temperature at various altitudes correlate with the muon rate at a high-latitude site (Ny-Ålesund, 78.9°N)?
• RQ2 Which temperature correction model best accounts for the atmospheric structure at polar latitudes and provides the most consistent reduction of seasonal variation?
• RQ3 Do temperature-corrected muon rates at high latitude exhibit residual periodicities, and how do these compare with lower-latitude measurements?
• RQ4 How do the derived temperature coefficients at 78.9°N compare with global results and geomagnetic cutoff dependence?

主な発見

Alpha (method)	Units	Result (α)	Pearson coeff.
ATE	%/km	-4.475 ± 0.057	-0.849
MMP	%/K	-0.170 ± 0.003	-0.756
MSS	%/K	-0.165 ± 0.002	-0.867
DCM	%/K	-0.326 ± 0.003	-0.891

• After pressure correction, muon rates still show a pronounced annual modulation largely driven by atmospheric temperature variations.
• Four temperature correction models yield α-values that are statistically consistent within 1–1.5% in corrected differential rates; residual seasonal variation is greatly reduced.
• The ATE, MMP, MSS, and DCM methods show negative temperature coefficients, with DCM giving α_DCM = -0.326 ± 0.003 %/K and strong negative Pearson correlation (−0.891).
• DCM yields a detailed, layer-specific temperature weighting based on Pearson correlations, emphasizing latitude-dependent atmospheric structure.
• Lomb–Scargle analysis after temperature correction suppresses the dominant annual peak and reveals additional near-two-year and longer-term periodicities.
• POLA-R results are qualitatively consistent with lower-latitude GMDN results in the trend of coefficients with geomagnetic cutoff, though sign differences exist for some methods (notably MMP).
• Residual neutron data from Oulu show similar time trends and solar-cycle influence, with stronger variations than muons.