On the Solar Cycle Variation of the Solar Diurnal Anisotropy of Multi-TeV Cosmic-ray Intensity Observed with the Tibet Air Shower Array

M Amenomori,X B Qu,M Takita,S Ozawa,Y Katayose,X J Bi,A Shiomi,T Shirai,M Ohnishi,K Kasahara,X Y Zhang,Haibing Hu,N Tateyama,I Ohta,K Kawata,L Xue,K Hibino,L K Ding,M Sakata,Q B Gou,H Nanjo,Ying Zhang,Zhaxisangzhu Zhaxisangzhu,Danzengluobu Danzengluobu,S W Cui,Labaciren Labaciren,H H He,Yi Zhang,N Hotta,H Y Jia,Y H Tan,L M Zhai,A F Yuan,S Udo,H Sugimoto,Y Zhang,F Kajino,M Shibata,T Saito ,G M Le ,C Feng ,Y Q Guo ,J Shao ,Z Yang ,H J Li ,H Wang ,K Yamauchi ,J L Zhang ,J S Liu ,Wen-Yun Chen ,H M Zhang ,Hongbo Hu ,Z Y Feng ,T Niwa ,T Nakajima ,A F Li ,D Chen ,Ze He ,Tetsuya Miyazaki ,M Y Liu ,X R Meng ,L L Jiang ,K Munakata ,Yu-Hui Lin ,Yuya Nakamura ,Takashi Sako ,W J Li ,C Kato ,Y Yamamoto ,H R Wu ,C Liu ,Shoji Torii ,H Tsuchiya ,X L Qian ,Z Feng ,H Lü ,M Kozai ,Masaki Nakamura ,J Huang ,T L Chen ,X X Zhou

doi:10.1051/epjconf/201920808012

Abstract

We analyze the temporal variation of the solar diurnal anisotropy of the multi-TeV cosmic-ray intensity observed with the Tibet air shower array from 2000 to 2009, covering the maximum and minimum of the 23rd solar cycle. We comfirm that a remarkable additional anisotropy component is superposed on the Compton-Getting anisotropy at 4.0 TeV, while its amplitude decreases at higher energy regions. In constrast to the additional anisotropy reported by the Matsushiro experiment at 0.6 TeV, we find the residual component measured by Tibet at multi-TeV energies is consistent with being stable, with a fairly constant amplitude of 0.041% ± 0.003% and a phase at around 07.17 ± 00.16 local solar time at 4.0 TeV. This suggests the additional anisotropy observed by the Tibet experiment could result from mechanisms unrelated to solar activities.

Highlights

Back in 1935, Compton and Getting [1] proposed an apparent effect that the observer would see an enhanced intensity in the direction of his motion when he moves with respect to the isotropic cosmic-ray plasma in the rest frame, and a decreased intensity in the direction opposite to his motion
We present the analysis of the solar diurnal anisotropy for the multi-TeV cosmic-ray intensity with data collected by the Tibet air shower array from 2000 to 2009, covering the maximum and minimum of the 23rd solar cycle, to examine the hypothesis mentioned above
We find the amplitudes at 4.0 TeV approximately twice as large as what the CG effect predicts in each period, that is to say, there is a remarkable additional anisotropy component superposing on the constant CG anisotropy

Summary

Introduction

Back in 1935, Compton and Getting [1] proposed an apparent effect that the observer would see an enhanced intensity in the direction of his motion when he moves with respect to the isotropic cosmic-ray plasma in the rest frame, and a decreased intensity in the direction opposite to his motion. Munakata et al [8] claimed an extra anisotropy superposed on the CG anisotropy at 0.6 TeV, with the constant phase at 15:00 local solar time (LT) and the amplitude varying from 0.008% to 0.043% which reveals a clear correlation with the solar activity. If these residual effects, both result from the solar modulation, a temporal variation of this additional anisotropy might be observed by the Tibet experiment. We present the analysis of the solar diurnal anisotropy for the multi-TeV cosmic-ray intensity with data collected by the Tibet air shower array from 2000 to 2009, covering the maximum and minimum of the 23rd solar cycle, to examine the hypothesis mentioned above

Experiment and Data Analysis

Results and Discussion

Conclusions