Ion-neutral reactions in the martian ionosphere

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Abstract

A number of reactions that might be important in the martian ionosphere have been studied and their rate coefficients have been measured with a pulsed flowing afterglow system. One of the most important of these is O+ + CO2 → O2+ + CO, which has a rate coefficient of about 10−9 cm+3 sec−1.

The ion chemistry is discussed and model ionospheres are constructed and compared with the Mariner IV electron concentration. Two interpretations seem possible: (1) the ions are mostly atomic (probably O+) and the peak electron concentration occurs at a neutral concentration of about 109 cm−3, and (2) the ions are mostly molecular (possibly with O2+ dominant) and the peak electron concentration occurs at a neutral concentration of about 5 × 1010 cm−3. However, the atomic ion model implies a rather low temperature which may prove to be a problem. The molecular ion model requires the neutral atmosphere to be mostly molecular near the electron density maximum which would probably indicate that mixing is important to greater altitudes than previously assumed.

Реферат

ИCCлeдobaлCя pяд peaкций, кoтopыe Moгли бы игpaть baж нuю poль b иoнoCфepe MapCa и кoэффициeнты ич CкopoCти были изMepe ны пoCpeдCтboM CиCтeMы иMпuльCнo-кoлeблющeгoCя пoCлeCbeчeния. b чиCл e тaкobыч oдниM из baжнeйшич яbляeтCя O+ + CO2 — O+2 + CO, кoэффициeнт CкopoCт и кoтopoгo яbляeтCя пpиблизитeльнo 10−9CM3 Ceк−1.

ЧиMичeCкий CoCтab иoнob пoдbepгaeтCя oбCuждeнию и Coo puжaютCя Moдeли иoнoCфep, кoтopыe CoпoCтabляютCя C элeктpoннoй кoнцeн тpaциeй Mapинepa IY. CuщeCтbuют, пobидиMoMu, дbe boзMoжныe интepпpeтaций: (1) иoны b бoльщинCтbe Cлuчaeb aтoMapныe (bepoятнo O++) и MaкCиMuM элeктpoннoй кoнцeнтpaции bCтpeчaeтCя пpи нeйтpaльнoй кoнцeнтpaции b пpиблизит eльнo 109 CM−3; (2) иoны пpeиMuщeCтbeннo Moлeкuляpны (boзMoжнo C пpeoблaдaниe M O+2+) и MaкCиMuM элeктpoннoй кoнцeнтpaции пpoиCчoдит пpи нeйтpaльнoй кoнцeнтpaции b пpиMepнo 5 × 1010 CM−3. Moдeль aтoMapныч иoнob, oднaкo, зaключaeт b Ceбe beCьMa низкuю тeMпepaтupu, чтo Moжeт oкaзaтьCя зaдaчeй. Для Moдeли Mo лeкuляpныч иoнob тpeбueтCя нeйpaльнaя aтMoCфepa, чтoбы быть нaибoлee M oлeкuляpнoй bблизи MaкCиMuMa элeктpoннoй плoтнoCти, чтo пobидиMoMu uкaзы baeт нa тo oбCтoятeльCтbo, чтo CMeщиbaниe baжнo для бoлee знaчитeльныч bыCoт, чeM paнee пpeдпoлaгaeMыч.

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