Propagation characteristics of very low latitude whistlers by ray tracing

Abstract Simultaneous measurement made in South China in January 1988 has already indicated that the nighttime whistlers observed at very low latitudes (geomagnetic latitudes, 10° to 14°) are attributed to field‐aligned propagation. On the other hand, a few researchers have suggested, based on the ray‐tracing computations, that nighttime whistlers at very low latitudes are due to nonducted propagation. To solve the discrepancy between the authors' experimental results and the previous ray‐tracing studies, extensive two‐dimensional ray‐tracing calculations have been made for the nonducted propagation of whistlers in the inner plasmasphere in a wide frequency range (1 to 10 kHz). The conditions for nonducted whistlers to penetrate through the ionosphere onto the ground have been discussed to clarify the difference from the experimental results reported here.