Computer simulations of the seasonal variations of the ionospheric equatorial anomaly in East Asia under solar minimum conditions

The previous dynamical, computer simulation model of the ionosphere at low latitudes of Chan H. F. and Walker G. O. (1984a, J. atmos. terr. Phys. 46, 1103; 1984b, J. atmos. terr. Phys. 46, 1113) has been modified to (1) include photoionization of molecular species NO⁺, N₂⁺ and O₂⁺ below 300km, (2) decouple the ionization and wind calculations below 180 km and (3) expand the geographical coverage to 46°N-30°S latitude. The first two modifications improved the model stability and the latter reduced the effect of the lateral boundaries on the equatorial anomaly. Results are presented for the representative seasonal months of January, April and July for East Asia, during solar minimum, comprising latitudinal-local standard time (120°E) contour plots of (1) the atmospheric pressure, (2) the computed meridional wind at 300 km, (3) the foF2 and (4) hmF2, together with latitudinal profiles of foF2 and N_T (electron content) showing the daytime development and nighttime decay of the equatorial anomaly.Comparisons have been made between the computer simulations and various experimental measurements of foF2, M(3000) F2 and N_T obtained in East Asia during periods of low solar activity. Most of the gross features of the development and decay of the equatorial anomaly at the various seasons were reproducible by the model simulations, the best agreement occurring for the equinoctial month of April.     

Positive and negative ion composition measurements in the D- and E-regions during the 26 February 1979 solar eclipse

Two rockets bearing quadrupole mass spectrometers capable of measuring both positive and negative ion composition were launched from Red Lake, Canada, during the solar eclipse. Both instruments had liquid helium cryopumps and shock-attaching conical samplers. The payloads also contained two Gerdien condensers to measure total positive and negative ion concentrations and ion mobilities. Attitude control systems aligned the payloads with the velocity vector throughout ascent and descent. The first rocket was launched so that the D-region was in darkness 35 ± 8 s on the upleg and about 150 ± 15 s on the downleg for the study of ionospheric decay processes. The second rocket was fired after totality into 75% solar illumination for the study of ionospheric recovery. The positive ion composition above 105 km exhibited a strongly increasing NO⁺/O₂⁺ ratio with time after second contact due to O₂⁺ charge transfer with NO and a sharply diminished ionization rate. However, in both nights, the ionization below 105 km was created mainly by energetic particle deposition as exemplified by the increased ion concentrations and the composition signatures of a particle event: asignificant enhancement of O₂⁺ below 105 km and large amounts of H₅O₂⁺ ions in the D-region which result from the O₂⁺ clustering scheme. H₅O₂ was the major ion in the upper D-region while H₇O⁺₃, H₉O₄⁺ and H₅O₂⁺ were dominant ions at lower altitudes. Numerous minor species were also detected. The negative ion distributions in both flights exhibited a distinct shelf at 83 ± 2 km, decreasing by more than an order of magnitude by 90 km and with minima near 75 km. In the 75–90 km range, a significant percentage of the negative ions had masses exceeding 160 a.m.u. Comparisons are made with prior negative ion measurements during similar daytime auroral zone absorption (AZA) events. Two striking characteristics of the precipitating particles were apparent from these and past observations in daytime AZA events: there is a near absence of low energy electrons capable of ionizing above about 105 km and there is'a significant spatial and/or temporal variability in the electron flux. This paper is devoted principally to a presentation of the ion composition measurements and associated uncertainties.     

The relationship between electron temperature and electron density under quiet conditions in the auroral zone

A theoretical model is described which predicts electron temperature in the day-time F-region above EISCAT on geomagnetically quiet days, given the observed values of electron concentration, ion temperature and heat conduction, the daily average of solar radiation at 10.7cm and the MSIS-86 model of the neutral atmosphere. The values predicted by the model agree very closely with the observed temperatures, both for average conditions and for individual days. On two occasions the onset of a geomagnetic disturbance after a period of quiet conditions was accompanied by a growing divergence between the predicted and observed values, which corresponds to an additional source of electron heating such as would be provided by low energy particle precipitation.     

论金融危机背景下房地产和谐发展的市场导向和相关条件

由美国金融危机引发的全球金融危机和经济衰退对我国房地产业发展带来了较大的冲击和影响,我国房地产业的政策环境和市场环境由此也发生了相应的变化。根据新形势,我国政府进一步明确了房地产业发展的政策导向,并结合市场的复苏提供了相应的对策措施,通过投资信贷市场和土地增量适时投放,来确保房地产业的“可持续发展”。     

Computed femur and tibia volumes and cranial capacity under near-optimal conditions of skeletal growth: Relation to geomagnetic dipole field intensity and other latitude-dependent climatic variables in archaeological North America and North Africa

Using computed femur (F) and tibia (T) volumes and cranial capacity (CC), the Pleistocene geomagnetic acromegalosis (PGMA) model of human evolution is tested in eight series of male skeleton sets (n = 123) from aboriginal North America and North Africa, the majority dated to the Holocene. The material was selected from the extensive multiracial osteometric data base previously assembled in the course of adult residual rickets (RR) skeletal plasticity research in archaeological populations of the Northern Hemisphere, controlling for optimal bone eutrophism, that is, for the absence of sunshine and calcium deficits and demographic stress. Six of the eight series are of hunter-gatherers, including a terminal Pleistocene mesolithic sample from the Maghreb. As predicted by PGMA, a clear osteotrophic response is observed between the F, T, and CC of these populations and their geomagnetic dipole field intensity (GMFI) backgrounds, here expressed in microteslas (μT); along with evidence that the GMFI-dependent osteotrophism is stronger near the sagittal plane. Slightly higher bioenvironmental correlations, also compatible with PGMA, are obtained with a composite environmental osteotrophism parameter (CEOT.J), which incorporates the reciprocal of the archaeological site's reconstructed mean July temperature as a synergizer of GMFI. In a final demonstration of the utility of the new computed osteovolumetrics, it is shown that Skhul IV, to judge from its size and proportions, is a hyperrobust pre-neanderthal male skeleton of early Late Pleistocene interglacial age, and belongs to the North African geographical race.