A disk drive includes a disk for storing information, a head with a
transducer that writes data to and reads data from the disk, and an AC
power source. The head is suspended adjacent to the disk and a flying
height gap exists at the head/disk interface. The AC power source
generates an AC exciter signal across the flying height gap that
discharges electrostatic charge at the head/disk interface. The head/disk
capacitance can be measured based on the AC exciter signal to sense the
flying height. The AC exciter signal can also alter an attraction force
between the head and the disk and thus control flying height. The AC
exciter signal can also be based on a flying height signal representative
of the head/disk capacitance and thus the flying height.