DE‐1 observations of ordinary mode and extraordinary mode auroral kilometric radiation

Abstract

Observations of auroral kilometric radiation (AKR) made with DE‐1 indicate the presence of both ordinary and extraordinary wave modes. Although the two modes usually occur separately, they are sometimes observed together. When both modes are present, the ordinary‐mode component tends to occur at lower frequencies and with lower amplitudes than those of the accompanying extraordinary‐mode component. On the other hand, the local electron gyrofrequency is an absolute lower frequency cutoff for both modes. Ordinary mode intensities are proportional to extraordinary mode intensities but less by roughly a factor of 50. Extraordinary mode ray paths are generally confined to a cone within 50° of the source magnetic field direction and ordinary mode emissions are typically observed outside of this cone. This behavior suggests that both components are produced within the same source region but are then refracted differently as they escape.