Temporal variations of thermospheric hydrogen derived from in situ measurements

Brinton, H. C.; Mayr, H. G.

doi:10.1029/ja076i025p06198

Cited by 50 publications

(10 citation statements)

References 9 publications

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“…Exospherie t•ansport and planetary escape further complicate the dynamics and contribute to upset the diffusive equilibrium conditions for,these constituents. So it_has been observed [Brinton and Mayr; .l•ha• the hydrogen concentration at 350 km pea'ks during night (thus exhibiting a density-temperature phase difference of the order of 12 hours), consistent with the theoretical predictions Kockarts and Nicolet [1962], McA#ee [1967], and Patterson [1966]. Temperature-density phase differences would therefore be quite understandable and should be expected, especially in the thermosphere at higher altitudes.…”

Section: •Discussionsupporting

confidence: 80%

Diffusion model for the phase delay between thermospheric density and temperature

Mayr¹,

Volland²

1972

J. Geophys. Res.

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Considering a two‐dimensional time‐dependent model in which the thermosphere dynamics is excited by the UV heat input within the thermosphere, it is shown that the wind‐induced variations in the diurnal component of atomic oxygen dominate over its temperature‐induced variations up to 200 km. The assumption of diffusive equilibrium is therefore in general not valid for O within the lower thermosphere. The effect of the diurnal wind circulation is to redistribute O so that (a) the diurnal variations in the [O]/[N2] and [O]/[O2] ratios are damped by about 20%, thus contributing to the maintenance of the nighttime F2 region, and (b) the maximum in the diurnal variation of O is shifted by one to two hours away from the temperature maximum toward noon, thus contributing significantly to the temperature‐density time lag at thermospheric heights above 200 km, where O becomes the major constituent.

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Section: •Discussionsupporting

confidence: 80%

Diffusion model for the phase delay between thermospheric density and temperature

Mayr¹,

Volland²

1972

J. Geophys. Res.

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“…This concentration is approximately a factor of two higher than that given by the Kockarts and Nicolet [1963] theoretical model, a result in substantial agreement with earlier in situ [8rinton and Mayr, 1971Mayr, , 1972 and airglow [Meier and Mange, 1973;Vidal-Madja.r et al, 19731 observations.…”

supporting

confidence: 80%

Winter bulge and diurnal variations in hydrogen inferred from AE‐C composition measurements

Brinton¹,

Mayr²,

Potter³

1975

Geophysical Research Letters

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The atomic hydrogen distribution at 250 km during December 1974 solstice has been inferred, considering charge exchange equilibrium, from Atmosphere Explorer‐C measurements of n(H+), n(O+), and n(O). An empirical model, derived from the observations by least square analysis in terms of spherical harmonics, has the following characteristics: (a) n(H) increases by as much as a factor of two between the summer and winter hemispheres, (b) the n(H) diurnal variation is largest at the equator where nmax/nmin = 3.2, the maximum occurring at 03h LT, and (c) the diurnal variation is larger in the winter hemisphere ( nmax/nmin = 2.6 at +40°) than in the summer (nmax/nmin = 2.3 at −40°). Similar analysis of the gas temperature derived from n(N2) measurements reveals that all n(H) and Tg spherical harmonic coefficients are anticorrelated. Both the diurnal and latitudinal (annual) n(H) and Tg amplitudes are in substantial agreement with the “zero flux condition,” in which exospheric flow dominates the hydrogen distribution. The observed diurnal phase lag of n(H) with respect to Tg is about one hour, agreeing with theory. During the period of measurement the observed mean global values of Tg and n(H) were 800K and 3.6 × 105 cm−3, respectively, the latter exceeding the Kockarts‐Nicolet model concentration by a factor of two.

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“…In a recent paper, Jacchia (1971) completely abandoned the temperature derivation from the semiannual effect in his model, stating that all difficulties in the description of the semiannual density variations could be removed if they were not related to temperature variations. Furthermore, Brinton and Mayr (1971) concluded from the small semiannual component in atomic hydrogen at mid latitudes that the semiannual variations in the exospheric temperature should be negligible there.…”

mentioning

confidence: 99%

Theoretical model for the latitude dependence of the thermospheric annual and semiannual variations

Mayr¹,

Volland²

1972

J. Geophys. Res.

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A three‐dimensional model for the annual and semiannual variations of the thermosphere is presented in which the energy and diffusive mass transport associated with global circulation are considered in a self‐consistent form. It is shown that these processes play a major role in thermosphere dynamics and thus account for a number of temperature and composition phenomena such as (1) the helium and oxygen bulges in the winter hemispheres at lower altitudes, (2) the relatively large temperature variations (∼26%) in the annual component, which exceed by a factor of 3 those temperatures inferred from the satellite drag data and would be much too large for a thermosphere in diffusive equilibrium, (3) the 7% variation of the exospheric temperature at the poles in the latitude dependent semiannual component associated there with a significant depletion of oxygen and helium during the equinox, and (4) the nearly height independent and relatively small amplitudes in the total mass density of the latitude dependent components that are responsible for the fact that the latitude variations of the semiannual effect have so far eluded observations from satellite drag data and that the globally uniform component of the semiannual effect appears to be relatively strong in comparison with the annual variations.

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Temporal variations of thermospheric hydrogen derived from in situ measurements

Cited by 50 publications

References 9 publications

Diffusion model for the phase delay between thermospheric density and temperature

Diffusion model for the phase delay between thermospheric density and temperature

Winter bulge and diurnal variations in hydrogen inferred from AE‐C composition measurements

Theoretical model for the latitude dependence of the thermospheric annual and semiannual variations

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