Diurnal and seasonal effects in <i>E</i> region low‐latitude nitric oxide

Stewart, A. I. F.; Cravens, T. E.

doi:10.1029/ja083ia06p02453

Cited by 45 publications

(17 citation statements)

References 15 publications

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“…Current results suggest an increase by a factor of about 2 from winter to summer, at latitudes of 25°-40°near solar minimum (e.g. Stewart and Cravens, 1978;Ge´rard and Noe¨l, 1986). This is sufficient to make appreciable changes to the E-region ionisation.…”

Section: The Production and Loss Of Nomentioning

confidence: 95%

Model results for the ionospheric E region: solar and seasonal changes

Titheridge

1997

Ann Geophysicae

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Abstract.A new, empirical model for NO densities is developed, to include physically reasonable variations with local time, season, latitude and solar cycle. Model calculations making full allowance for secondary production, and ionising radiations at wavelengths down to 25 A s , then give values for the peak density N K E that are only 6% below the empirical IRI values for summer conditions at solar minimum. At solar maximum the difference increases to 16%. Solar-cycle changes in the EUVAC radiation model seem insufficient to explain the observed changes in N K E, with any reasonable modifications to current atmospheric constants. Hinteregger radiations give the correct change, with results that are just 2% below the IRI values throughout the solar cycle, but give too little ionisation in the E-F valley region. To match the observed solar increase in N K E, the high-flux reference spectrum in the EUVAC model needs an overall increase of about 20% (or 33% if the change is confined to the less well defined radiations at (150 A s ). Observed values of N K E show a seasonal anomaly, at mid-latitudes, with densities about 10% higher in winter than in summer (for a constant solar zenith angle). Composition changes in the MSIS86 atmospheric model produce a summer-to-winter change in N K E of about !2% in the northern hemisphere, and #3% in the southern hemisphere. Seasonal changes in NO produce an additional increase of about 5% in winter, near solar minimum, to give an overall seasonal anomaly of 8% in the southern hemisphere. Near solar maximum, reported NO densities suggest a much smaller seasonal change that is insufficient to produce any winter increase in N K E. Other mechanisms, such as the effects of winds or electric fields, seem inadequate to explain the observed change in N K E. It therefore seems possible that current satellite data may underestimate the mean seasonal variation in NO near solar maximum. A not unreasonable change in the data, to give the same 2:1 variation as at solar minimum, can produce a seasonal

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Section: The Production and Loss Of Nomentioning

confidence: 95%

Model results for the ionospheric E region: solar and seasonal changes

Titheridge

1997

Ann Geophysicae

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“…Both individual NO profiles and zonally and time-averaged latitude/altitude distributions were presented. Future experimental studies should combine the latitude (or magnetic latitude) and longitude coverage of the 105-km AE-C studies Stewart and Cravens, 1978] with the altitude coverage of this AE-D study. That is, threedimensional data sets should be constructed and analyzed.…”

Section: Discussionmentioning

confidence: 99%

“…This relation was convolved with the instrumental sensitivity function in order to give a curve of growth function between the instrumental counts recorded during an integration period and the slant column density of NO. Stewart and Cravens [1978] presented this function for the UVNO spectrometer on the AE-C satellite. The function for the AE-D instrument is virtually identical to the AE-C one if the AE-C function is multiplied by a factor of 1.83.…”

Section: Measurements and Data Analysismentioning

confidence: 99%

The latitudinal gradient of nitric oxide in the thermosphere

Cravens¹,

Gérard²,

Stewart³

et al. 1979

J. Geophys. Res.

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The ultraviolet nitric oxide spectrometer (UVNO) experiment on the Atmosphere Explorer D (AE-D) satellite measured thermospheric nitric oxide during the winter of 1974-1975 using resonant fluorescence from the 1-0 gamma band of the molecule. Almost complete latitude coverage was obtained, but the observations were confined to morning local times close to 0900. The 1-0 gamma band intensity profiles measured by the instrument were inverted to provide vertical profiles of the NO number density between about 90 and 200 km. Typically, the measured NO concentrations reached a maximum between altitudes of 100 and 110 km, and more NO was observed at higher latitudes than at low latitudes, in agreement with previous observational studies. The shape of the NO profile was also found to be a function of latitude, with a plateau appearing in the profile near 130 km for low latitudes and mid-latitudes in the winter hemisphere.

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“…The spectrometer data were acquired during the daylight hours. Stewart & Cravens (1978) have found that [NO] tends to decrease, by a factor of up to 2, between sunset and sunrise. Sternberg and Ingham (1982) carried out a seminal programme of observations on the night sky continuum over the 4100-8200 A range from the Haute-Provence Observatory for a period of several years near sunspot maximum.…”

Section: Rocket Investigationsmentioning

confidence: 99%

Cause of terrestrial nightglow continuum

Bates

1993

Proc. R. Soc. Lond. A

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Since the nightglow’s green continuum was discovered over 40 years ago the theory that it arises from the NO 2 air afterglow has been generally accepted so that its intensity is regarded as a useful measure of the abundance of nitric oxide in the lower thermosphere. This theory is shown to be untenable. Observational evidence points unambiguously to a novel source: metastable oxygen molecules colliding with ambient gas molecules and thereby forming complexes that dissociate by allowed radiative transitions.

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Diurnal and seasonal effects in E region low‐latitude nitric oxide

Cited by 45 publications

References 15 publications

Model results for the ionospheric E region: solar and seasonal changes

Model results for the ionospheric E region: solar and seasonal changes

The latitudinal gradient of nitric oxide in the thermosphere

Cause of terrestrial nightglow continuum

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