EMP effects are pretty short range, they effect a large area onlt if they are generated high enough in the atmosphere (>few 100km) such that the particles produced can spread over a large area as they arrive at the surface.

The local range of the effects of particles arriving at the surface is similair to that of lightning. You can think of an EMP device as the equivalent of starting a large number or lightning strikes over a large area (although EMP does not cause lightning).

Solar flares do not generate EMP, they do produce an electric current in structures near the poles and do inject low energy particles into the atmosphere - again mostly near the poles.

http://eo.nso.edu/MrSunspot/answerbook/polarity.html