The diurnal variation of absorption of wireless waves

The total absorption of wireless waves reflected from region F has been measured over Christchurch, New Zealand. The diurnal variation in this quantity has been investigated under conditions which exclude absorption at the top of the wave trajectory; the results refer to the absorption which is thought to occur in region E. The variation has been compared with that given by Appleton's theory of absorption in a simple Chapman region. The practical results are found to agree with the theory, as far as the diurnal variation is concerned, both in summer and in winter. The ratio of the summer absorption to the winter absorption is, however, smaller than it should be according to the theory. This discrepancy is discussed. It is shown also that when the waves are returned from the intense E region, instead of region F , the absorption is of the same order of magnitude, a fact which indicates that the absorbing zone is beneath region E in conformity with Appleton's theory.