2017, 37(6): 667-674.
doi: 10.11728/cjss2017.06.667
Abstract:
By analyzing the characteristics of cosmic ray flux evolution, the approaching of CMEs could be identified, and the geomagnetic disturbance could be forecasted. The modulation of cosmic by CMEs could be derived by comparing the fluxes from different directions, and the parameters, such as Interplanetary Magnetic Field (IMF) and direction, could be derived. In this paper, data obtained by Nagoya muon telescope are used, and southward and eastward flux are chosen for investigation in detail. The results show that the evolutions of muon fluxes from the two directions share similar pattern before the strong geomagnetic storm, while there is a 2-hour phase delay between them. It is analyzed that the cosmic rays corresponding to the two directions went into and out the CME successively and the time difference is about 2 hours. The correlation coefficient and flux difference of the fluxes in eastern and southern, concluding the phase of the southern flux is moved backward two hours or not, are calculated respectively. As CMEs approaching, the correlation coefficient with southward phase change is significantly higher than that without phase change, and the flux difference with the southward phase change is much lower than that without phase change. However, the coefficient and the flux difference began to get close to each other when CMEs arrive at the Earth. And the above parameters of phase changed disparity amplitude even exceeded the unchanged one. The characteristics are also found in the geomagnetic storms with Kp=9 from 2003 to 2005. The muon flux before the great geomagnetic storm on December 14, 2006 is analyzed, and the study found that it is coincident with the above characteristics. Therefore, directional muon detection possesses a unique ability to remote sensing CMEs propagation through the difference of the flux evolution from different directions.
