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Mayr, H. G.

Publications and source records attributed to Mayr, H. G..

At least 181 records · Page 10
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NASA NTRS1972

Empirical model of global thermospheric temperature and composition based on data from the OGO-6 quadrupole mass spectrometer

An empirical global model for magnetically quiet conditions has been derived from longitudinally averaged N2, O, and He densities by means of an expansion in spherical harmonics. The data were obtained by the OGO-6 neutral mass spectrometer and cover the altitude range 400 to 600 km for the period 27 June 1969 to 13 May 1971. The accuracy of the analytical description is of the order of the experimental error for He and O and about three times experimental error for N2, thus providing a reasonable overall representation of the satellite observations. Two model schemes are used: one representing densities extrapolated to 450 km and one representing densities extrapolated to 120 km with exospheric temperatures inferred from N2 densities. Using the best fit model parameters the global thermospheric structure is presented in the form of a number of contour plots.

Hedin, A. E.↗
NASA NTRS1972

Note on the semi-annual effect in the thermosphere

The semi-annual variation in the thermospheric density is discussed in terms of the spatial and temporal variations in the solar heat input. Two heat sources are considered: the solar heat input associated with the semi-annual migration of the sun, and the auroral heat associated with the semi-annual component in magnetic storms. It is shown that the relatively large global component in the semi-annual effect of the total mass density can be explained by the lack of advective loss which otherwise damps the latitude dependent components in the annual and semi-annual variations, and the significant latitude dependence in the semi-annual variations of composition and temperature can be tied to the diffusion process which is induced by the thermospheric circulation.

Volland, H.↗
NASA NTRS1972

The problem of the boundary conditions in thermosphere dynamics.

A simple analytic solution for the generation and propagation of tidal waves at thermospheric heights is presented. It is used to show that a unique solution of tidal wave propagation within the thermosphere depends on the boundary conditions of the model, and that radiation conditions lead to such a unique solution.

Volland, H.↗
NASA NTRS1972

Magnetic storm characteristics of the thermosphere

Energy and diffusive mass transport associated with the thermospheric circulation are considered in a self-consistent, though mathematically relatively simple form to describe in a three-dimensional two-constituent model magnetic storm characteristics in composition (N2, O, and He), temperature and mass-density. It is shown that during disturbed conditions the latitudinal variations of composition and gas temperature T sub g reflect the local nature of the magnetic storm heat input assumed to be primarily confined to the auroral zones. Thereby T sub g and N2 increase, He decreases and O remains constant through the auroral zones at exospheric heights (due to the superposition of temperature and diffusion effects) in agreement with OGO-6 mass spectrometer measurements. In contrast, the magnetic storm response in the total mass density is characterized by a strong world-wide component and a relatively insignificant increase toward the poles with the density peak occurring between two (poles) and eight (equator) hours after the maximum energy input, in substantial agreement with satellite drag data.

Mayr, H. G.↗
NASA NTRS1972

A modified Monte Carlo model for the ionospheric heating rates

A Monte Carlo method is adopted as a basis for the derivation of the photoelectron heat input into the ionospheric plasma. This approach is modified in an attempt to minimize the computation time. The heat input distributions are computed for arbitrarily small source elements that are spaced at distances apart corresponding to the photoelectron dissipation range. By means of a nonlinear interpolation procedure their individual heating rate distributions are utilized to produce synthetic ones that fill the gaps between the Monte Carlo generated distributions. By varying these gaps and the corresponding number of Monte Carlo runs the accuracy of the results is tested to verify the validity of this procedure. It is concluded that this model can reduce the computation time by more than a factor of three, thus improving the feasibility of including Monte Carlo calculations in self-consistent ionosphere models.

Mayr, H. G.↗
NASA NTRS1972

A numerical study of a three dimensional spherical thermospheric density and wind model

Numerical calculations of the generation and propagation of the two important fundamental symmetric tidal wave modes - the diurnal mode (1, 1, 1,) and the semidiurnal mode (2, 2, 2) - were performed applying a realistic model thermosphere and taking into account heat conduction and the temporally and spatially varying ion-neutral collision number. Both wave modes are predominantly generated by the solar EUV heat input. It is shown that the latitude structure of the (1, 1, 1)-mode which is identical with the Hough function(1, -1) within the lower non-dissipative atmosphere degenerates into the spherical function P sub 1, 1 at thermospheric heights. The pressure field of this mode constitutes the observed pressure bulge of the thermosphere, the diurnal component of which peaks at 15 h L. T. The electric polarization field of the geomagnetic Sq current generates a significant fraction of this wave mode at F layer heights. This wave component shifts the total horizontal wind system to earlier times by about 1 hour in agreement with ionospheric observations. The latitude structure of the (2, 2, 2) mode is identical with the Hough function (2, 2) within the lower non-dissipative atmosphere. It degenerates to the spherical function P sub 2, 2 at thermospheric heights.

Volland, H.↗
NASA NTRS1972

A two component model of the diurnal variations in the thermospheric composition

A self-consistent, two-dimensional, two-component diffusion model is presented to describe the diurnal component of thermosphere dynamics. In the regions where oxygen and helium are the minor constituents, diffusion is shown to increase the amplitudes of these constituents and to advance the times of their diurnal maxima by several hours with respect to the gas temperature and the major species. Both effects are in basic agreement with satellite observations. The diffusion process is relatively insignificant for temperature, total mass density, and wind fields. The magnitude of the temperature-density phase delay is discussed with respect to its dependence on the electron density distribution.

Mayr, H. G.↗
NASA NTRS1972

Diffusion model for the phase delay between thermospheric density and temperature.

Consideration of a two-dimensional time-dependent model in which the thermosphere dynamics is excited by the UV heat input within the thermosphere, showing 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 the diurnal variations in the forbidden O/forbidden N2 and forbidden O/forbidden O2 ratios are damped by about 20%, thus contributing to the maintenance of the nighttime F2 region, and 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.

Mayr, H. G.↗
NASA NTRS1972

A global empirical model of thermospheric composition based on OGO-6 mass spectrometer measurements.

A global empirical model for magnetically quiet conditions has been developed to describe longitudinally averaged OGO-6 N2, O, and He densities (in the altitude range 400 to 600 km) by means of an expansion into spherical harmonics. The annual asymmetric component in N2 density corresponds to an increase of about 400 K between winter and summer poles, which is about a factor of three greater than in the Jacchia model. However, the corresponding oxygen component at satellite altitudes reflects an increase between winter and summer comparable to that in the Jacchia model; this implies that at 120 km atomic oxygen increases by more than a factor of two between summer and winter poles. The amplitude of the symmetric semiannual component in N2 is larger at the poles than the equator. At the poles, the N2 variation corresponds to a temperature decrease of about 70 K from mid-April to mid-July. At low latitudes, the daily temperature maximum occurs close to 16 hours local time, nearly in agreement with radar backscatter observations.

Hedin, A. E.↗
NASA NTRS1972

Effect of Modified Thermal Conductivity on the Temperature Distribution in the Protonosphere

At typical protonospheric electron densities, the electron mean free path is long enough that the coefficient of thermal conductivity is no longer given by Spitzer's expression. The effect on the temperature profile of using the corrected expression for conductivity is investigated. The corrected thermal conduction coefficient is density-dependent and has a more complicated temperature dependence than the coefficient applicable to higher density plasmas. The results indicate that the effect is not negligible even under quiet conditions and at low latitudes.

Mayr, H. G.↗