EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Cosmic Ray Flux Correlation between McMurdo and Jang Bogo Neutron Monitor Stations vs. Time Lag

Ekawit Kittiya1, Waraporn Nuntiyakul1, Achara Seripienlert2, Paul Evenson3, Alejandro Saiz4, David Ruffolo4, and Sueyon Oh5
Ekawit Kittiya et al.
  • 1Chiang Mai University, Faculty of Science, Physics and Materials Science, Muang, Chiang Mai, Thailand (,
  • 2National Astronomical Research Institute of Thailand (NARIT), Chiang Mai 50180, Thailand (
  • 3Department of Physics and Astronomy, University of Delaware, Newark, DE 19716, USA (
  • 4Department of Physics, Faculty of Science, Mahidol University, Bangkok 10400, Thailand (,
  • 5Department of Earth Science Education, Chonnam National University, Gwangju 61186, South Korea (

A neutron monitor is a large ground-based detector responding to the flux of cosmic ray particles in space by measuring atmospheric secondary neutrons. Any ground-based detector is sensitive to cosmic rays from a specific range of directions in space. In particular, a particle arriving from a specific sky direction with a specific rigidity (momentum per unit charge) was necessarily moving from a certain direction in space, called the asymptotic direction. McMurdo and Jang Bogo neutron monitor stations are Antarctic stations with similar geomagnetic latitudes but slightly different longitudes. From December 17, 2015 to January 9, 2017, six of the eighteen neutron counters from McMurdo had been transferred to Jang Bogo (with full transfer to Jang Bogo completed in December 2017). We present an analysis of the correlation of the cosmic ray flux between the McMurdo and Jang Bogo stations, during the time when both were operating, with ten-second time resolution. Although highly correlated, there are significant differences, including a systematic time lag of approximately 16 minutes between the data from the two stations. Although McMurdo observes with similar asymptotic directions to Jang Bogo, the response-weighted average directions still have a substantial difference of 21.9 degrees in geographic longitude, so with Earth’s rotation, time-independent anisotropy effects should induce a lag of 88 minutes.  Because the observed lag of 16 minutes is intermediate between 0 and 88 minutes, the joint observations reveal structure in the interplanetary cosmic-ray density that is consistent with a combination of simultaneous temporal variations and non-simultaneous variations with direction (i.e., anisotropy). The research is supported in part by a TA/RA scholarship (active recruitment) of Chiang Mai University and Thailand Science Research and Innovation via Research Team Promotion Grant RTA6280002.

How to cite: Kittiya, E., Nuntiyakul, W., Seripienlert, A., Evenson, P., Saiz, A., Ruffolo, D., and Oh, S.: Cosmic Ray Flux Correlation between McMurdo and Jang Bogo Neutron Monitor Stations vs. Time Lag, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4215,, 2022.

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