The Variations of Galactic Cosmic Ray Intensity and the K Category of Magnetic Disturbances

The relationship between the variations of galactic cosmic ray intensity and geomagnetic storms from 1966 to 1983 is studied in this paper. The variations of the cosmic ray intensity during a sudden commencement pulse Si doesn't show an obvious decrease. Avery small Forbush decrease appears during gradual commencement storm G_c. On the other hand, there is a very obvious Forbush decrease during sudden commencement storm S_c. Then S_c storms are classified into S_A, S_B, S_D. S_d and S_b storms on the basis of Kindex. The results of analysis show that Forbush decrease of cosmic ray intensity during S_A storms is the most obvious and the decreasing rate and recovering rate are also the fastest. The amplitutes of Forbush decrease are descending in the order of S_A, S_B S_Dand S_d storms. Their decreasing rates and recovering rates become slowing in the same order. But the cosmic ray intensity during S_b storms has no obvious decrease. According to corresponding relationship between Kcategory of magnetic disturbances and. interplanetary disturbances, a relation between cosmic ray intensity variations and interplanetary disturbances is obtained.