Answer
(b) are related to the lower Van Allen belt.
Work Step by Step
Two large donut shaped regions at altitudes of several thousand kms are called Van Allen radiation belts. In the lower Van Allen belt, light emissions called auroras occur - the aurora borealis or northern lights in the northern hemisphere and the aurora australis or southern lights in the southern hemisphere. Thus aurora dominantly happens during solar disturbances due to charged particles entering earth's atmosphere at both pole following the magnetic field lines.
