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121.
The dissociation of N2 by electron impact and by e.u.v. photo-absorption is studied, and it is shown that the forbidden predissociation of the numerous 1Πu and 1Σu+ valence and Rydberg states of N2 in the 11–24eV energy range is the dominant mechanism for N atom production. By measuring the absolute emission cross sections for the e.u.v. singlet bands of N2 and by using the generalized oscillator strength data of Lassettre (1974), it has been possible to construct a detailed model of the total N2 dissociation cross section which is in good agreement with the measurements of Winters (1966) and Niehaus (1967) and provides some insights into the maximum possible yield from dissociative excitation. The total cross section for exciting N2 e.u.v. radiation in the 800Å–1100Å wavelength range has been measured and found to have a value of 3.4 ×10?17 cm2 at 100 eV under optically thin conditions. Although this result implies that large fluxes of e.u.v. photons should be excited in auroral substorms and in the airglow, they are not observed, and we show that this development is a consequence of radiation entrapment and predissociation. The total cross section for dissociating N2 by electron impact is given for optically thin and thick media. And some questions concerning the energy budget of a magnetospheric storm which are raised by these results, are discussed. 相似文献
122.
123.
We have analysed the variations of inclination in 13 satellite orbits as they pass slowly, under the action of air drag, through 15th-order resonance with the geopotential, when successive equatorial crossings are 24° apart and the ground track repeats after 15 rev. The size and form of the change in inclination are determined mainly by the values of the geopotential harmonics of 15th order and odd degree, and (with l = 15, 17, 19, …) in the usual notation. Our analysis gives values of these coefficients up to l = 33 as follows:
l | 109C?l,15 | 109S?l,15 |
15 | ?23.5 ± 0.8 | ?7.7 ± 0.8 |
17 | 6.3 ± 1.5 | 5.6 ± 1.5 |
19 | ?25.1 ± 2.5 | ?7.3 ± 2.3 |
21 | 27.8 ± 3.6 | ?0.7 ± 3.4 |
23 | 17.1 ± 4.1 | 13.9 ± 4.8 |
25 | ?1.1 ± 3.0 | 8.5 ± 4.2 |
27 | 10.0 ± 3.3 | 6.7 ± 2.7 |
29 | ?9.4 ± 3.5 | 0.1 ± 4.7 |
31 | 10.1 ± 5.4 | 3.8 ± 5.6 |
33 | 1.1 ± 5.7 | 3.1 ± 5.8 |