[_Microft]

If I had to guess, I would say that Earth's magnetic field is used in directional drilling to tell which way your drill head is going and that the solar storm distorts Earth's magnetic field.

[SoftTalker]

Wonder why they don't use gyros. Too much vibration?

[_Microft]

They might be - this was only an attempt to make sense of the first comment in the context of this submission.