Spectrograms of broad-band ELF/VLF goniometer data obtained from ground based measurements made at Halley, Antarctica (L 0 =4.3, con jugate near St. Anthony, Newfoundland) have shown the presence of discrete line radiation of magnetospheric origin, in the frequency range 1-4 kHz. The properties of this radiation are broadly similar to Power Line Harmonic Radia tion (PLHR), studied from ground based observations made at Siple, Antarc tica (L =4.1, conjugate-Roberval, Quebec), although there are some interesting differences. Line radiation observed at Halley, is never regularly spaced in frequency by 120 Hz, as one may expect if signals from the Newfoundland power distribution system (60 Hz fundamental) are entering the magneto sphere, and being amplified. Instead, frequency spacings are widely distributed about mean values between 50 to 90 Hz. The lines are observed to trigger emissions and often exhibit 2 hop amplitude modulation, which demonstrates that they are of magnetospheric origin. Events occur mostly in quiet to moderate geomagnetic conditions, and during the late af ternoon period of local time. Arrays of lines are often observed to drift upwards together in fre quency. Line bandwidths are 20-30 Hz-much larger than the bandwidths of locally generated induction lines. We show that the line spacing of ,.., 80 Hz is too large to correspond to sideband separation for waves of equatorial field strength ,.., 10 pT, and we investigate the conditions required for effective particle trapping by the wave array, of the type described by NuNN (J. Plasma Phys., 11, 189, 1974). It is proposed that the line radiation either originates in the signals which enter the magnetosphere from Newfoundland, or is 'naturally' generated, possibly by a linear instability which takes place if the electron distribution is unstable in restricted ranges of wave frequency and wave number.