A tentative evaluation of kinematic viscosity for ionospheric regions

Yerg, Donald G.

doi:10.1029/jz057i002p00217

Cited by 7 publications

(2 citation statements)

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“…Because the thermosphere is convectively stable and has very high kinematic viscosity (Yerg, 1952), structures in the wind on small spatial scales (200 km or less) are not predicted to be significant (Killeen & Roble, 1988; Killeen et al., 1988; Smith et al., 1988). The net effect of convective stability and high kinematic viscosity is to suppress small‐scale vortices and convective overturning, thereby producing a wind field that is expected to be smooth, laminar, and not strongly dependent on altitude above 200 km.…”

Section: Introductionmentioning

confidence: 99%

Characterizing Unexpectedly Localized Slowing of the Thermospheric Cross‐Polar Jet of Neutral Wind Over Alaska in the Midnight Sector

Itani

Conde

2021

JGR Space Physics

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Earth's thermosphere is the region of atmosphere from E  90 km up to E  500-1,000 km altitude depending on solar-cycle conditions. Its lower edge is defined by the transition to a positive vertical temperature gradient above the mesopause, whereas the upper limit is generally taken to be the height at which the mean free path exceeds one scale height. The upper portion of the thermosphere corresponds to the altitude region occupied by low Earth-orbiting spacecraft. Understanding the details of the weather in the thermosphere is thus important for orbital prediction and for space debris collision avoidance. The dominant terms involved in orbital predictions are obtained from the direct application of well-known equations of Newtonian mechanics. However, operational responses to space debris hazards are driven by the uncertainty in these predictions, on the time scales of days to a week or so ahead. The largest contribution to this uncertainty comes from aerodynamic drag effects, due to imperfect knowledge of the (vector) wind and (scalar) mass density fields of the ambient atmosphere. Thus, in order to reduce these uncertainties, an accurate thermospheric model, including wind, is needed.

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Section: Introductionmentioning

confidence: 99%

Characterizing Unexpectedly Localized Slowing of the Thermospheric Cross‐Polar Jet of Neutral Wind Over Alaska in the Midnight Sector

Itani

Conde

2021

JGR Space Physics

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“…Large values of v are to be expected in the higher atmosphere, ' and equation (1) suggests that it may be necessary to treat the higher atmosphere as a viscous fluid.…”

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confidence: 99%

Viscosity in the high atmosphere

Yerg¹

1955

J. Geophys. Res.

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The kinematic viscosity η/ρ approaches infinity as the density ρ approaches zero, since the results of kinetic theory show that the molecular viscosity η is independent of density. The elementary viscosity derivations use a linear velocity profile which implies near infinite streaming velocities as the density becomes small. The streaming velocities must be finite, and the velocity profile must have an upper and a lower limit in the atmosphere. It is shown that the viscous stress must approach zero with decreasing density when the velocity profile is bounded. Either the velocity gradients or the corrected viscosity coefficients become small in the higher atmosphere. The viscous effect depends on a length scale representative of the wind shear and is a maximum in the lower F‐region for scales comparable to those representative of the air currents studied in synoptic meteorology.

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Winds in the ionospheric regions

Deb

1953

Journal of Atmospheric and Terrestrial Physics

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A tentative evaluation of kinematic viscosity for ionospheric regions

Cited by 7 publications

References 2 publications

Characterizing Unexpectedly Localized Slowing of the Thermospheric Cross‐Polar Jet of Neutral Wind Over Alaska in the Midnight Sector

Characterizing Unexpectedly Localized Slowing of the Thermospheric Cross‐Polar Jet of Neutral Wind Over Alaska in the Midnight Sector

Viscosity in the high atmosphere

Winds in the ionospheric regions

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