Certain of the ISEE-1 observations between the plasmasphere and the auroral zone have revealed the emission cone of auroral kilometric radiation (AKR) unaffected by plasmaspheric refraction. At some distance from the source, this cone produced a sharp low-frequency boundary in the AKR signals, which was displaced above the the cyclotron frequency. The variation of this boundary, plus other aspects of the AKR signals, indicated that the AKR emission cone closed toward a hollow, roughly forty-five degree limit cone with decreasing frequency, duplicating the behavior previously found with ISIS-1 at the opposite end of the AKR spectrum.