During the year 2015 two great geomagnetic storms (Dst<-200nT) occurred on 17 March and 22 June. These two geomagnetic storms have similarities. They occurred during the same decreasing phase of the sunspot cycle 24. The interplanetary and magnetospheric environments were calm before the beginning of the storms. Both events were due to Coronal Mass Ejections (CME)and High Speed Solar Wind (HSSW). Variations of the solar wind velocity and the Bz component of the interplanetary magnetic field (IMF) were also similar. Two key features that are different for these storms are UT time of the beginning(04:45UT for 17March and 18:33UT for 22June) and season (equinox and solstice). The comparison of the impact of the storms on the Earth ionosphere and magnetosphere have been performed using diverse parameters including global ionospheric maps (GIMs) of vertical total electron content (VTEC), data from individual GNSS receivers, ionosondes, magnetometers and instruments from different space missions. Visualizing GIM data as the difference of VTEC between consecutive days allowed understanding better the effect of the storms as a function of time of the beginning of the storm and of the season. It is shown that the presence or absence of scintillations in GNSS signals during these 2 storms in African longitude sector is clearly related to the local time at a given station at the beginning of the storm.