Journal cover Journal topic
Annales Geophysicae Sun, Earth, planets, and planetary systems An interactive open-access journal of the European Geosciences Union
Ann. Geophys., 12, 139-146, 1994
© European Geosciences Union 1994
31 Jan 1994
A study of quasi-periodic ELF-VLF emissions at three Antarctic stations: evidence for off-equatorial generation?
K. Morrison, M. J. Engebretson, J. R. Beck, J. E. Johnson, R. L. Arnoldy, L. J. Cahill ,Jr, D. L. Carpenter, and M. Gallani Abstract. The spatial extent and temporal behaviour of quasi-periodic (QP) intensity modulations of 0.5-2 kHz ELF-VLF signals were investigated in a comparative study of data collected at the Antarctic stations of South Pole (L=14), Halley (L=4), and Siple (L=4). Frequently, the waveforms of ELF-VLF signals simultaneously received at each site were identical. Although of similar frequency structure, the waveforms of the accompanying Pc3 magnetic pulsations did not show a one-to-one association. Whereas both are dayside phenomena, QP emissions occur over a smaller range of local times, and have a maximum of occurrence later in the day closer to local noon. QP emissions are identified with the periodic modulation of the electron pitch-angle distribution by the propagation of ULF compressional fast-mode waves through a region. However, contrary to previous ideas, rising-tone emissions do not represent the frequency-time signatures of such waves. In addition to generation close to the equatorial plane, we propose an additional high-latitude source of QP emissions. These emissions are associated with regions of minimum B produced by the dayside compression of the magnetosphere close to the magnetopause. Model magnetic field calculations of these minimum-B regions as a function of magnetic local time and invariant latitude are presented.

Citation: Morrison, K., Engebretson, M. J., Beck, J. R., Johnson, J. E., Arnoldy, R. L., Cahill ,Jr, L. J., Carpenter, D. L., and Gallani, M.: A study of quasi-periodic ELF-VLF emissions at three Antarctic stations: evidence for off-equatorial generation?, Ann. Geophys., 12, 139-146,, 1994.
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