Comets P/Brorsen-Metcalf and C/Okazaki-Levy-Rudenko appeared successively in 1989 and displayed various disturbances of their magnetospheres. We observed two cases of a phenomenon in which a disconnection event of the cometary plasma tail (on August 13 and November 16, 1989) was followed by a terrestrial magnetic storm (on August 14 and November 17). A survey of solar flares suggsts that an identical solar flare excited successively the cometary magnetosphere and the Earth's magnetosphere in each case. The average velocities of the shock front in interplanetary space were estimated by using the magnetospheric disturbances of both the comets and the Earth together with the assumed responsible solar flare. It is speculated from the results that the propagation of the shock front associated with the flare is not symmetric with respect to the radial axis from the flare region of the Sun. ¿ American Geophysical Union 1995