Dawn‐dusk gradient of the precipitation of low‐energy electrons over the polar cap and its relation to the interplanetary magnetic field

We report a clear indication of (1) the existence of the dawn-dusk gradient of the intensity distribution of low-energy electrons over the northern and southern polar caps, (2) the reversal of the gradient over the two polar caps, and (3) the dependence of the direction of the gradient on the interplanetary magnetic field By component. These features have a striking similarity with the distribution of the magnitude of the dawn-dusk component of the electric field in the polar cap.