Dogleg

PhD student working on geomagnetic storms- these storms would cause changes in the earth's magnetic fields of hundreds of nanoTeslas, and cause electric fields of a few (<10) volts per km. Only reason why power networks are affected is because they span hundreds of Kms.

The geomagnetic storms are generally over long periods- low frequencies. From a quick glance at Wikipedia, this is unlike an EMP.

I really doubt they'd affect equipment like HDDs.