High speed coronal mass ejection CME event with fast solar energetic particles SEP is identified using the LASCO-SOHO coronagraph and GOES proton flux data (>10 Mev) respectively. The fast SEP could be produced when the high speed CME shock front collides with the preceding CME. This project focuses on those SEP events when the storm disturbance index Dst is higher than -80 nT, that is, relatively quiet geomagnetic field period with no geomagnetic storm. The ionosphere response to these events is detectable by the TEC and normalized foF2 indices. Deviation of ionosphere index of 70% of the monthly median was observed in severe cases. The success of a storm prediction model that uses quiet day ionosphere index would be affected by perturbation of the baseline by the SEP events, and the details would depend on the baseline subtraction criteria used. Separation of the SEP event from the usual magnetic storm Dst event would provide a better baseline estimate for input to a storm predication model. The terrestrial gamma ray flash produced by one such event (Dst about -40 nT) was captured by RHESSI (04-21-2002). The SEP spectrum derived from atmospheric bremsstrahlung correlates with the ionosphere response. The empirical result might be used to study the interacting CME speed and therefore forecast its arrival time on the ionosphere in quiet geomagnetic condition.