Analysis of the nighttime ionosphere suggests that the reactions 0 + q-N2 -• (rate v•) -• NO + q-N and 0 + q-Os -• (rate v2) -• 0s + q-O are 3 X 10 -•a cm a sec -x and 3 X 10 -• cm • sec -x, respectively, within a factor of about 3. An additional requirement is that v•/vs --0.1 within a factor of about 2. No important temperature dependence is evident for either process at thermopause temperatures. The dissociative recombination rates a(Os +) for 0s + q-e -• 0 q-O and a(NO +) for NO + q-e -• N q-0 are shown to have a ratio of about unity within a factor of 2. It is suggested that the temperature dependence for both rates lies within Te -•.ø•ø-s for T •> 200øK. Upper limits for the reaction 0s + q-Ns -• NO + q-NO are determined to be 10 -•s cm • sec -• near 400øK and 10 -x4 cm • sec -• at 1000øK. It is demonstrated that the acceptance of approximately 10 -7 cma sec -• for a(Os +) and a(NO +) at 300øK, which is roughly in accord with both laboratory measurements and the daytime solar E-region flux, requires the existence of a nighttime E-region source of ionization. The possible contributions of meteors, scattered H Lyman a, and H Lyman tg as sources at night are briefly discussed. x Based on a paper presented at the 5th International Space Science Symposium, Florence, May 12-16, 1964.Anticipating the results, some nighttime production sources of the E region will be discussed.The need for such sources will be shown to be compatible with a rather orthodox viewpoint of the day and night behavior of the E region.As is customary, cgs units are used throughout the paper, except for height, which is in kilometers.
DECAY SCHEMES FOR ATOMm OX•mENIOnS AND ELECTRONS is obeyed also by the electrons in the region 4859 4860 where n(O +) • n(e). This equation is applicable to electrons, even though the loss of electrons is by dissociative recombination.with the positive molecular ions 0•. + and NO +. Radiative attachment of electrons is insignificant at these heights and below [see, e.g., Ratcli#e et al., 1956]. The electron decay equation is dn(e) -[n(e) --n(O+)]o•)n(e) (5) dt where -+) = + (No +) (Molecular nitrogen ions are negligible.) a, represents the mean dissoeiative recombination coefficient, defined as +) + +) O/D : +) + +) The use of a mean coefficient is justified by the fact that a(O• +) •_ a(NO+), as will be shown in the next section. Davis [1961] has given the solution of the null Rieatti equation as dy dX q-Q(X)y + R(X)y 2 = 0 1 e xødx C q-R(t)e -xød• dt Y Thus (5) is solved (for constant a, as WILLIAM SWIDER, JR.