A qualitative explanation of the diurnal variation of chorus

Diurnal variation of chorus. One of the most regular and consistent features of the very low frequency (VLF) emissions known as chorus is the diurnal variation of occurrence. Storey [1953] noted that chorus occurrence peaked at dawn at Cambridge; later Allcock [1957] and Pope [1957] showed that the diurnal peak varied almost linearly with geomagnetic latitude, being near dawn at the lower latitudes and near noon at the high latitudes. Attempts have been made to reduce the scatter in the data by measuring the peak occurrence in auroral time [Brice and Ungstrup, 1963].