A mechanism for the generation of a low-frequency (1--562 Hz) magnetic noise, occurring on the auroral field lines (Gurnett and Frank, 1977), is proposed in terms of an electromagnetic lower hybrid instability. The instability can be driven either by electron temperature anisotropies or by field-aligned currents. Several observed properties of the noise, such as (1) its occurrence from the same region where broadband electric field noise is observed, (2) its frequency range, (3) its tentative identification as a whistler type mode, and (4) its burstlike nature, can be explained by the theory.