The probability distributions of echo durations as measured on a 33 Mc/sec horizontally beamed radar at Kühlungsborn, G.D.R. (54°07′N, 11°46′E) indicate significant differences between echo durations during night- and day-time. These differences are attributed to attachment during night, whereas the strong radiation detachment of electrons during day-time leaves effectively no negative ions. The nocturnal attachment rate found from the difference in the probability distributions is higher than the rates deduced from the aeronomical processes hitherto known in the meteor height range. The probable attachment processes, the rate coefficients and particle densities are listed as far as known.