Monitoring the upper atmospheric temperature and interplanetary magnetic field with the GRAPES-3 muon telescope

Abstract

We study the influence of variations in the upper atmospheric temperature and interplanetary magnetic field on the cosmic ray induced atmospheric muon flux measured by the GRAPES-3 experiment over 22 years (2001--2022) of data; spanning three solar cycles: the declining phase of Solar Cycle 23, the full Cycle 24, and the rising and maximum phases of Cycle 25. Located in Ooty- India, the GRAPES-3 large area (560\,$m^2$) muon telescope detects $\sim$4 billion muons daily above 1\,GeV, with an angular resolution of $\sim$4${}^{\circ }$, enabling a statistical precision $<$0.01\% on the hourly muon rate. After accounting for the effect of atmospheric pressure variations, we compare this data with the upper atmospheric temperature inferred from NASA's MERRA-2 dataset as well as magnetic field data from the ACE and WIND spacecraft at Lagrange point L1. A simultaneous iterative fitting method employing Fast Fourier Transforms and a narrow band-pass filter reveals the temperature and magnetic field coefficients to be ${\alpha }_T=-0.2241\pm 0.04(stat.)\pm 0.0220(syst.)\%K^{-1}$ and ${\gamma }_M=-0.574\pm 0.027(stat.)\pm 0.011(syst.)\%{\text{nT}}^{-1}$, respectively, for an assumed hadronic attenuation length $\lambda$=120 g cm${}^{-2}$, underscoring the potential of the GRAPES-3 muon telescope to serve as a real time monitor of the upper atmospheric temperature or interplanetary magnetic field.

References in corpus (2)

• Measurement of the Electrical Properties of a Thundercloud Through Muon Imaging by the GRAPES-3 Experiment
• Observation of muon intensity variations by season with the MINOS Near Detector