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1.
Diurnal variation of the dayside, ionospheric, mid-latitude trough in the southern hemisphere at 800 km: Model and measurement comparison 总被引：1，自引：0，他引：1
J.J. Sojka W.J. Raitt R.W. Schunk J.L. Parish F.J. Rich 《Planetary and Space Science》1985,33(12):1375-1382
Our high latitude ionospheric model predicts the existence of a pronounced “dayside” trough in plasma concentration equatorward of the auroral oval in both the Northern and Southern Hemispheres for solar maximum, winter, and low geomagnetic activity conditions. The trough in the Southern Hemisphere is much deeper than that in the Northern Hemisphere, with the minimum trough density at 800 km being 2 × 103 cm−3 in the Southern Hemisphere and 104 cm−3 in the Northern Hemisphere. The dayside trough has a strong longitudinal (diurnal) dependence and appears between 11:00 and 19:00 U.T. in the Southern Hemisphere and between 02:00 and 08:00 U.T. in the Northern Hemisphere. This dayside trough is a result of the auroral oval moving to larger solar zenith angles at those universal times when the magnetic pole is on the antisunward side of the geographic pole. As the auroral ionization source moves to higher geographic latitudes, it leaves a region of declining photoionization on the dayside. For low convection speeds, the ionosphere decays and a dayside trough forms. The trough is deeper in the Southern Hemisphere than in the Northern Hemisphere because of the greater offset between the geomagnetic and geographic poles. Satellite data taken in both the Northern and Southern Hemispheres confirm the gross features of the dayside trough, including its strong longitudinal dependence, its depth, and the asymmetry between the Northern and Southern Hemisphere troughs. 相似文献
2.
We have studied the extent to which diffusion-thermal heat flow affects H+ temperatures in the high-latitude topside ionosphere. Such a heat flow occurs whenever there are H+?O+ relative drifts. From our study we have found that at high-latitudes, where H+ flows up and out of the topside ionosphere, diffusion-thermal heat flow acts to reduce H+ temperatures by 500–600 K at altitudes above about 900 km. 相似文献
3.
The electron density observations made using ESRO-1 and ESRO-4 near solar maximum and solar minimum, respectively, show a strong longitudinal variation at middle latitudes in the southern hemisphere. The peak of this sinusoidal variation occurs at around 7 hr U.T. and decreases exponentially in size from about 300 km (depending on local time, season, solar flux) with increasing or decreasing altitude. During local summer conditions the amplitude is larger than during local winter conditions and particularly high values occur near the solar maximum. Selecting data from magnetically quiet periods, a quantitative model is constructed of the UT-eflect in the topside electron densities. 相似文献
4.
We propose that a strong, hydrodynamic shock forms around the space shuttle and at times detaches. In our model this shock generates hydrodynamic, strong turbulence downstream, and we find the level of this turbulence to be sufficient to account for the observed heating of electrons. 相似文献
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B.L.N. Kennett A.W.H. Bunch J.A. Orcutt R.W. Raitt 《Earth and Planetary Science Letters》1977,34(3):439-444
Systematic travel time inversion techniques have been applied to first arrival travel times from a number of seismic refraction profiles on the crest and flanks of the East Pacific Rise to generate bounds on the possible velocity-depth distributions. The greatest variability in structure occurs within 5 Myr of the rise crest. The generally similar character of the bounds on the velocity distributions for ages greater than 5 Myr indicates that the most rapid aging occurs within 5 Myr of the crest, though the mantle velocity increases systematically with age. The nature of the bounds on the velocity distribution for the range of velocities associated with layer 3 requires that the velocity distribution within layer 3 increase with depth. 相似文献
7.
The continuity, momentum and energy hydrodynamic equations for an O+-H+ ionosphere have been solved self-consistently for steady state conditions when a perpendicular (convection) electric field is present. Comparison of the H+ temperature profiles obtained with and without the electric field show that the effect of the electric field is to enhance the H+ temperature at high altitudes from about 3600 to 6400 K. Due to ion heating by the electric field, there is a net reduction of O+ in the F2-region as compared with the case of a non-convecting ionosphere. When the reduction of O+ is neglected, the electric field acts to increase the H+ outward flux from 8.3 × 107 to 2.7 × 108 cm?2 sec?1 for average ionospheric conditions. However, when the reduction of O+ is included, there is a net reduction in the outward H+ flux. Nevertheless, the convection electric field still results in an increase in the rate of depletion of the F-re m?1 electric field. 相似文献
8.
Three ionospheric probes were carried on the ESRO-4 satellite, a spherical gridded probe with swept potential collecting positive ions, a Langmuir probe measuring electron temperature and vehicle potential, and a fixed potential gridded probe measuring fluctuations in total ion density. ESRO-4 was placed in a polar orbit of apogee 1177 km, perigee 245 km on 22 November 1972 and ionospheric data of excellent quality were obtained until the spacecraft's re-entry on 15 April 1974. The instrumentation is described and early results are presented. 相似文献
9.
The total ion-density probe on the satellite ESRO-4 has been used to monitor the position of the boundary of the high-latitude ionospheric irregularity zone. The diurnal behaviour of this boundary suggests the appearance of a distinct night-time sub-auroral irregularity zone. Possible irregularity production mechanisms are discussed. 相似文献
10.
The scientific constraints on the measurement of suprathermal electron fluxes in the 1–500 eV energy range in the auroral zone are discussed. These constraints are used to define the characteristics of an electrostatic analyser to measure such fluxes. The design and calibration of such an instrument are described.The application of the instrument to measure details of atmospheric absorption of low energy electrons by utilizing its high energy resolution, and the application to measure detailed variations of spectrum and pitch angle distribution by utilizing its high sensitivity are discussed with reference to a number of rocket flights made from the northern auroral zone. 相似文献