X (black circles) and Z (triangles) component magnetic perturbations from the central Canadian CANOPUS Chain at 3:30 UT on Feb. 22 1997. Corresponding model output is shown by solid and dotted lines. The dark gray region on the X axis corresponds to a latitudinally restrained region of eastward electrojet (ionospheric electric current flow), and the light gray region to a broad westward electrojet poleward of it. There is very good agreement between the data and the model result (note one Z point at −50 nT which has the most disagreement). Large gradients in both magnetic components arise near the interface of the electrojets at 67 degrees of CD (centered dipole) latitude.