Effective recombination coefficient in the E region

Abstract

On the assumption that the ion production rate at E-layer maximum varies diurnally with the cosine of the solar zenith angle, a relative value of an 'instantaneous' recombination coefficient can be derived which changes only slightly with the time of day. These changes are attributed to the effect of vertical ion drift due to the S_q current system. Consequently, the absolute value of the true recombination coefficient can be derived with the conventional comparison method at the (appropriately redefined) focus of the S_q current system. An estimate of the drift perturbations of the coefficient can be obtained by using the proportionality between the drift gradient and the magnetic north component (X') of the S_q variations in the horizontal magnetic field on the ground. The relatively small diurnal variations found for the value of the instantaneous recombination coefficient in contrast with the large diurnal variation obtained by the 'comparison' methods indicate that it is possible to think of a single daytime value of the coefficient for this region. The implications of this single value (~1 × 10^-8 cm³/sec) in terms of ionic chemistry are also examined.