Effective eddy diffusion coefficient and atmospheric composition in the lower thermosphere

Shimazaki, Tatsuo

doi:10.1016/0021-9169(71)90011-0

Cited by 87 publications

(34 citation statements)

References 23 publications

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“…Also, our results support the notion that two-dimensional turbulence is a characteristic of the MLT (Kelley et al, 2009). The eddy diffusion coefficient inferred by Lübken (1997) from measurements of the turbulent energy dissipation rate in the summer polar mesosphere can be approximated by formulas suggested by Shimazaki (1971): …”

Section: Discussionmentioning

confidence: 99%

Eddy diffusion coefficients and their upper limits based on application of the similarity theory

Vlasov

Kelley

2015

Ann. Geophys.

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Abstract. The equation for the diffusion velocity in the mesosphere and the lower thermosphere (MLT) includes the terms for molecular and eddy diffusion. These terms are very similar. For the first time, we show that, by using the similarity theory, the same formula can be obtained for the eddy diffusion coefficient as the commonly used formula derived by Weinstock (1981). The latter was obtained by taking, as a basis, the integral function for diffusion derived by Taylor (1921) and the three-dimensional Kolmogorov kinetic energy spectrum. The exact identity of both formulas means that the eddy diffusion and heat transport coefficients used in the equations, both for diffusion and thermal conductivity, must meet a criterion that restricts the outer eddy scale to being much less than the scale height of the atmosphere. This requirement is the same as the requirement that the free path of molecules must be much smaller than the scale height of the atmosphere. A further result of this criterion is that the eddy diffusion coefficients K ed , inferred from measurements of energy dissipation rates, cannot exceed the maximum value of 3.2 × 10 6 cm 2 s −1 for the maximum value of the energy dissipation rate of 2 W kg −1 measured in the mesosphere and the lower thermosphere (MLT). This means that eddy diffusion coefficients larger than the maximum value correspond to eddies with outer scales so large that it is impossible to use these coefficients in eddy diffusion and eddy heat transport equations. The application of this criterion to the different experimental data shows that some reported eddy diffusion coefficients do not meet this criterion. For example, the large values of these coefficients (1 × 10 7 cm 2 s −1 ) estimated in the Turbulent Oxygen Mixing Experiment (TOMEX) do not correspond to this criterion. The K ed values inferred at high latitudes by Lübken (1997) meet this criterion for summer and winter polar data, but the K ed values for summer at low latitudes are larger than the K ed maximum value corresponding to the criterion. Analysis of the experimental data on meteor train observations shows that energy dissipation with a small rate of about 0.2 W kg −1 sometimes can induce turbulence with eddy scales very close to the scale height of the atmosphere. Our results also explain the discrepancy between the large cooling rates calculated by Vlasov and Kelley (2014) and the temperatures given by the MSIS-E-90 model because, in these cases, the measured eddy diffusion coefficients used in calculating the cooling rates are larger than the maximum value presented above.

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Section: Discussionmentioning

confidence: 99%

Eddy diffusion coefficients and their upper limits based on application of the similarity theory

Vlasov

Kelley

2015

Ann. Geophys.

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“…Within the transport code the molecular diffusion coefficients are calculated according to Banks and Kockarts (1973). Eddy diffusion coefficient profile can be varied using the parameterisation given by Shimazaki (1971).…”

Section: Modelling the Spe Effects In The Magnetic Cutoff Transition mentioning

confidence: 99%

Latitudinal extent of the January 2005 solar proton event in the Northern Hemisphere from satellite observations of hydroxyl

et al. 2007

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Abstract. We utilise hydroxyl observations from the MLS/Aura satellite instrument to study the latitudinal extent of particle forcing in the northern polar region during the January 2005 solar proton event. MLS is the first satellite instrument to observe HO x changes during such an event. We also predict the hydroxyl changes with respect to the magnetic latitude by the Sodankylä Ion and Neutral Chemistry model, estimating the variable magnetic cutoff energies for protons using a parameterisation based on magnetosphere modelling and the planetary magnetic index K p . In the middle and lower mesosphere, HO x species are good indicators of the changes in the atmosphere during solar proton events, because they respond rapidly to both increases and decreases in proton forcing. Also, atmospheric transport has a negligible effect on HO x because of its short chemical lifetime.The observations indicate the boundary of the proton forcing and a transition region, from none to the "full" effect, which ranges from about 57 to 64 degrees of magnetic latitude. When saturating the rigidity cutoff K p at 6 in the model, as suggested by earlier studies using observations of cosmic radio noise absorption, the equatorward boundary of the transition region is offset by ≈2 degrees polewards compared with the data, thus the latitudinal extent of the proton forcing in the atmosphere is underestimated. However, the model predictions are in reasonable agreement with the MLS measurements when the K p index is allowed to vary within its nominal range, i.e., from 1 to 9 in the cutoff calculation.

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“…The eddy viscosity coefficient is related to the eddy diffusion coefficient and the Prandtl number. The eddy diffusion coefficient was taken from a formula by Shimazaki [1971]. The Prandtl number is approximately unity in the lower atmosphere around 100 km height.…”

Section: Data Analysis Methodsmentioning

confidence: 99%

Momentum balance of dayside E region neutral winds during geomagnetically quiet summer days

Maeda¹,

Fujiwara²,

Nozawa³

1999

J. Geophys. Res.

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Abstract. An intent of this paper is to study dayside quiet time E region neutral momentum balance in the auroral ionosphere. Neutral wind vectors were obtained by using the European Incoherent Scatter (EISCAT) Common Program 2 (CP-2) data between 98 and 119 km height from 1100 to 1300 UT (from 1200 to 1400 LT and from 1400 to 1600 MLT) on June 15 and 16, 1993. Individual forcing terms in the neutral momentum equation were determined from the derived neutral winds with the MSISE-90 model. In order to calculate the velocity change with time including advection, designated as the time-dependent term, and the viscous force in the neutral momentum equation, a polynomial fitting procedure was applied to perform the vertical and time differentiation of the derived neutral winds. Below 106 km height, the time-dependent term was greater than the pressure gradient force except for the meridional component at 98 km height on June 15. Between 110 and 116 km height, the pressure gradient force was in the same order of magnitude as that of the Coriolis force and the time-dependent term was smaller than these two. The neutral wind flow was nearly perpendicular to the pressure gradient force. At 119 km height, the viscous drag was in the same order of magnitude as those of the pressure gradient and Coriolis forces and greater than the Pedersen and Hall drags. The magnitude of ion drag was -7% of the Coriolis force at this height level.

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Effective eddy diffusion coefficient and atmospheric composition in the lower thermosphere

Cited by 87 publications

References 23 publications

Eddy diffusion coefficients and their upper limits based on application of the similarity theory

Eddy diffusion coefficients and their upper limits based on application of the similarity theory

Latitudinal extent of the January 2005 solar proton event in the Northern Hemisphere from satellite observations of hydroxyl

Momentum balance of dayside E region neutral winds during geomagnetically quiet summer days

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