By comparing recordings made at Pamatai, Tahiti, with those from the magnetometer array operated by the Institute of Geological Sciences, it is observed that Pi's occur at low latitudes on the dayside of the Earth coincidentally with Pi2's recorded (and thought to be generated) near the local midnight sector. The low-latitude daytime Pi's have different spectral components to the corresponding nighttime events and do not show a preferred local time of occurrence. There does not appear to be any large or systematic difference in the arrival of day- and nighttime events. In view of the discrepancies which remain in the understanding of the generation of nighttime Pi2's at mid- and high-latitudes it is not yet possible to place these observations within a context of reasonable interpretation. It is shown that the existence of daytime Pi's in a narrow belt around the equator is an important fact which must be considered in any overall description of the generation and transmission processes resulting from transient phenomena within, or acting upon, the magnetosphere. © 1980.
Stuart, W. F., & Barsczus, H. G. (1980). Pi’s observed in the daylight hemisphere at low latitudes. Journal of Atmospheric and Terrestrial Physics, 42(5), 487–497. https://doi.org/10.1016/0021-9169(80)90009-4