hundred km above the F2-peak. The horizontal extent of the region of reduced ionization is hard to estimate. North-south dispersion will spread the cloud for a distance of perhaps 1000-3000 km about the latitude of injection (cf Section 2.6, in particular Table 7 and Figure 3). As a result of zonal (eastwest) winds, it is likely that the depleted region extends completely around the globe at the latitude of injection, but some non-zonal behavior may occur. The magnitude of the reduction in ionization may range from 40% to a factor of 2 in electron density at night, and significantly less in the daytime, perhaps as low as 10-20%. Note that these estimates are not based on detailed calculations or observation, and must be verified. Section 3.2.4 outlines how one would undertake the difficult task of verifying this prediction. 3.2.3 Dissociative recombination of H;>0+ and 0H+ (Bernhardt — prepared after the Workshop) If we believe that condensation of water vapor in rocket exhaust is on the order of 10% or less, then water plays an important role in F-layer modification. The charge exchange reaction with 0+ is + + -9 3 H^O + 0 + H^O + 0 , rate: 2.3 x 10 cm /sec . The charge exchange reaction rate is known within ± 10% (Howard, Dundle and Kaufman, 1970). The dissociative recombination process for the H20+ is less well known. The (H20+ + e ) dissociative recombination (D-R) rate is estimated to —9 3 be 3 x 10 cm /sec, based on D-R rates of similar ions (Biondi, 1973). The dissociative channels for H20-h are: (See Wadt, Hay and Cartwright, 1977.) The last two channels (6 _and 7) involve 0+2H formation. They arise from predissociation of the 0H(Zi ) that is produced by channel ^4). OH(zl ) may also be lost by radiative transition to the ground electronic state. Three channels for 0H( E+) loss are:
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