Inhomogeneous transverse electric fields and wave generation in the auroral region: A statistical study

We use data from the Freja satellite to investigate the importance of local ized transverse DC electric fields for the generation of broadband waves re sponsible for ion heating in the auroral region. Theoretical models indicat e that shear in the plasma Row perpendicular to the geomagnetic field can g enerate waves in a broad range around the ion gyrofrequency for parallel cu rrents significantly below the threshold of the current-driven electrostati c ion cyclotron instability. We compare in situ data with laboratory measur ements and theoretical predictions, and we find that inhomogeneous electric fields might well be important for the generation of waves in the auroral region.