Linsley's EAS time structure method for the primary cosmic ray spectrum at LAAS A. Iyono1, H. Matsumoto1, K. Okei2, S. Tsuji2, S. Ohara3, N. Ochi4, T. Konishi5, N. Takahashi6, I. Yamamoto7, T. Nakatsuka8, T. Nakamura9, N. Ohmori9, and K. Saito10 1Dept. of Fundamental Science, Okayama University of Science, Okayama 700-0005, Japan 2Kawasaki Medical School, Kurashiki 701-0192, Japan 3Nara University of Industry, Nara 636-8503, Japan 4Yonago National College of Technology, Tottori 683-8502, Japan 5Kinki University, Osaka 577-8502, Japan 6Dept. of Physics, Hirosaki University, Hirosaki 036-8561, Japan 7Dept. of Information and Computer Engineering, Okayama University of Science, Okayama 700-0005, Japan 8Okayama Shoka University, Okayama 700-86011, Japan 9Kochi University, Kochi 780-8520, Japan 10Ashikaga Institute of Technology, Ashikaga 326-8558, Japan
Received: 12 Oct 2010 – Revised: 18 Feb 2011 – Accepted: 23 Mar 2011 – Published: 01 Sep 2011
Abstract. We have installed a shift register system of extensive air show (EAS) particles
in a compact EAS array built on the rooftop of the Faculty of Engineering building in the campus of Okayama University of Science
and being operated since April 2006 as part of Large Area Air Shower (LAAS) experiments ,
in order to register each arrival time of EAS particles within 5 μs.
Detector simulations based on the database obtained from one of
the standard cosmic ray propagation simulator in the atmosphere (AIRES)
have also been carried out
and the procedures to estimate the primary cosmic ray energy from the Linsley's method have been developed and examined.
Applying Linsley's method to the EAS data obtained by our EAS arrays and the simulation results, we derived the energy spectrum
from 1016 eV to 1019.5 eV.
Consequently, we obtained the power-law index
of −3.2 (+0.46−0.8)
in the primary energy range of 1016 eV to 1018.5 eV,
and obtained that a change around 1018 eV appeared
if not taking account of the zenith angle distribution of primary cosmic rays.
We compared the obtained energy spectrum with other experimental data above 1016 eV energies,
and showed the two components of power-law energy spectra well described our data.
We also showed the improvement of energy resolution
by applying the restriction of zenith angle of primary cosmic rays in our simulation results,
as well as the potential of the Linsley's method with a compact EAS array.
Citation: Iyono, A., Matsumoto, H., Okei, K., Tsuji, S., Ohara, S., Ochi, N., Konishi, T., Takahashi, N., Yamamoto, I., Nakatsuka, T., Nakamura, T., Ohmori, N., and Saito, K.: Linsley's EAS time structure method for the primary cosmic ray spectrum at LAAS, Astrophys. Space Sci. Trans., 7, 335-344, doi:10.5194/astra-7-335-2011, 2011.