Tape Degaussing is a process where magnetic media is exposed to a powerful, alternating magnetic field. Degaussing removes any previously written data, leaving the media in a magnetically randomized (blank) state. Erasers and tape degaussers must subject the media to an powerful, alternating magnetic field.
To erase recorded data, it is necessary for the strength of the degaussing field to be greater in value that the coercivity of the magnetic media. Coercivity is the magnetic field strength, rated in oersteds (Oe), required to change the magnetic orientation of the magnetic material.