Abstract
Measurements of nitric oxide mixing ratios have been made by the Halogen Occultation Experiment on the Upper Atmosphere Research Satellite over an altitude range extending from 15 to 130 km on every spacecraft sunrise and sunset event with the exception of about 8% downtime. Selected NO profiles from the first few months of observations were examined with emphasis on the relation between geomagnetic disturbances and enhanced NO in the lower thermosphere. During a large geomagnetic storm on November 8–9, 1991, HALOE obtained 15 NO sunrise profiles along the ∼50°N latitude circle. A factor of 3 increase in NO mixing ratio above ∼115 km at this latitude and a one to two day decay time were observed. The measured NO longitude/altitude cross section on this day shows a longitudinal asymmetry in the NO distribution with a maximum near the geomagnetic pole. From approximately one month's data, a latitude/altitude cross section of zonal mean NO mixing ratio was calculated. An example of such cross sections demonstrates a strong positive correlation between geomagnetic activity and thermospheric NO globally. This auroral forcing has a larger effect on increasing NO at high latitude than at low latitude.
Highlights
NO mixingratiowascalculatedA. n exampleof suchcross Prior to HALOE on UARS, satellite measurementsof sectionsdemonstrateasstrongpositivecorrelationbetween thermosphericnitric oxide had been made by the AtmosgeomagnetiacctivityandthermospherNicO globally.This phericExplorersatellites(AE - C and-D) during1974and auroralforcinghasa largereffectonincreasinNgO athigh 1975 [Barth et al, 1973; Cravenset al., 1985] and the Solar latitude than at low latitude
Detaileddescriptionof the HALOE experimenits given in a paperbyRusselelta!. (1993)
I. Stewart,Globalmorphologyof nitric oxide in the lower E region, J
Summary
Abstract.Measuremenotfsnitricoxidemixingratios The responseof thermospherincitric oxideto solarand havebeenmadebytheHalogenOccultatioEnxperimeonnt geomagneticactivityhas beenstudiedby usingtheoretical the Upper AtmosphereResearchSatelliteover an altitude models [Solomonet al., 1982; Cravensand Killeen, 1988, rangeextendinfgrom15to 130kmoneveryspacecrasfutn- Siskindeta!., 1989;Robie, 1992]. N exampleof suchcross Prior to HALOE on UARS, satellite measurementsof sectionsdemonstrateasstrongpositivecorrelationbetween thermosphericnitric oxide had been made by the AtmosgeomagnetiacctivityandthermospherNicO globally.This phericExplorersatellites(AE - C and-D) during1974and auroralforcinghasa largereffectonincreasinNgO athigh 1975 [Barth et al, 1973; Cravenset al., 1985] and the Solar latitude than at low latitude. MesospherEexplorer(SME) satellitebetweenJanuary1982 and August!986 [Barth et al, 1988; Siskindet al., 1989; Introduction. The distributionsof nitric oxidein differ- betweenlow latitudeNO andsolarcycle[Barthet al., 1988; ent latitudinalregionsreflectthe combinedeffectof solar Barth, !992]. The model simulationby Robie (1992) brief,theoccultatioenxperimenmt easurethseabsorptioonf showedthat the low latitudeenhancementosf NO during solarenergyby atmosphergicasesduringsatellitesunrise geomagnetisctormsaremorelikelycausedby enhancement andsunseet vents.TheNO channeilsoneof thefourgasfil- in solarsoftX-raysasproposedby Barth[Barthet al., 1988; ter radiometer channelsin the HALOE instrument.
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