Completely agree, requirements are key and often badly defined due to the customers’ lack of knowledge of the intricacies of the system. You are correct to ask for clarity or it could come back to bite you later on.
I’ve just had a spec through from a BA which consists entirely of screenshots of an existing system with no technical definitition of any of the requested fields so relate to this right now.
I think it means the electric field created within Earth’s atmosphere that is responsible for lightning as opposed to the (electro)magnetic field which forms the magnetosphere around Earth and makes compasses work.