Appraising the impact of space radiation on the terrestrial environment

The Near-Earth space environment is impacted by various radiation sources like galactic cosmic rays, solar storms, geomagnetic storms, etc. In the present paper, we have estimated the impact of space radiation observed during the last four cycles. We have observed that during solar cycle 24, there were fewer solar radiation storms than during its three preceding solar cycles. In terms of solar radiation storm strength, solar cycle 22 recorded a maximum intensity of S4 (severe radiation storm) of 43000 pfu. In comparison, the maximum intensity of solar cycle 24 was 6530 pfu (S3 type). We have concluded that the intensity of an X-class flare did not predict the intensity of the ensuing geomagnetic activity. The flares with less intensity in X-rays, e.g. M-class and C-class flares, can give rise to stronger radiation storms. Using the NOAA scales, we have compared the data of intense radiation storms with geomagnetic storms of higher intensity. This analysis has revealed that there were only 11 days during solar cycles 23 and 24 where the maximum solar radiation storm (solar particle event) coincided with a period of severe geomagnetic storming. On comparison of monthly neutron count (cosmic ray intensity) relative to the average of the last 20 years, we also deduced that the neutron count was 7.12