Diurnal variation of the dayside, ionospheric, mid-latitude trough in the southern hemisphere at 800 km: Model and measurement comparison

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.     

Effect of diffusion-thermal processes on the high-latitude topside ionosphere

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.     

ESRO-1 AND ESRO-4: A model of the U.T. effect in electron density at middle latitudes of the southern hemisphere

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.     

Heating of electrons in turbulence around the space shuttle

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.     

再论花岗岩按照Sr-Yb的分类:标志

2006年作者曾经按照Sr=400×10~(-6)和Yb=2×10~(-6)作为标志将花岗岩分为埃达克岩、喜马拉雅型花岗岩、浙闽型花岗岩和广西型花岗岩,在浙闽型中又分出南岭型(Sr100×10~(-6)和Yb2×10~(-6)),于是花岗岩被分为5类。Sr=400×10~(-6)和Yb=2×10~(-6)是根据阿留申群岛中的Adak岛的资料得出来的。本文统计了全球花岗岩6000多个数据(其中,埃达克型花岗岩为2810个,喜马拉雅型花岗岩636个,浙闽型花岗岩1183个,南岭型花岗岩1518个,广西型花岗岩142个,总共6289个),统计的结果,各类花岗岩的地球化学特征大致如下:(1)埃达克型花岗岩富Al_2O_3和Sr,贫Y和Yb,具较高和变化的铕异常,绝大多数样品的Sr300×10~(-6),Yb2.5×10~(-6)(当Sr=400×10~(-6)～600×10~(-6)时Yb值最大,Sr超过600×10~(-6),Yb降低至2×10~(-6)),Al_2O_3在14%～18%之间,Eu/Eu~*大多在0.6～1.2范围;(2)喜马拉雅型花岗岩贫Sr和Yb,具中等的Al_2O_3和变化的Eu/Eu~*,Sr300×10~(-6)和Yb2×10~(-6)(少数Sr300×10~(-6)),Al_2O_3为13%～17%,Eu/Eu~*为0.2～1.0;(3)浙闽型花岗岩贫Sr富Yb,Sr在40×10~(-6)～400×10~(-6)之间,Yb1.5×10~(-6),Al_2O_3和Eu/Eu~*的变化类似喜马拉雅型花岗岩,Al_2O_3为12%～17%,Eu/Eu~*为0.4～1.0;(4)南岭型花岗岩以很低的Sr、Al_2O_3和Eu/Eu~*以及很高的Yb而不同于上述各类花岗岩,通常Yb1.5×10~(-6),Sr100×10~(-6)(Yb变化大,绝大多数2×10~(-6);当Yb在2×10~(-6)～8×10~(-6)时,部分样品Sr可100×10~(-6),但很少200×10~(-6));Al_2O_314%,集中在11%～13%之间,Eu/Eu~*0.7,大多0.4;Yb越大,Sr越低,负铕异常越明显。文中讨论了花岗岩Sr-Yb分类的意义,指出本分类适用于产于大陆和海洋的绝大多数中酸性岩浆岩(可能不适用于一部分特别富铁和钾的花岗岩,如具有高Sr和Yb特征的广西型花岗岩)。不同类型的花岗岩主要反映了源区压力的不同,而源区成分、温度、部分熔融程度、水和挥发分的加入以及岩浆混合等的影响可能是次要的。文中指出,该分类的依据、其实质,是熔体与残留相平衡的理论。与浙闽型花岗岩平衡的残留相是斜长石,与喜马拉雅型花岗岩平衡的是斜长石+石榴石,与埃达克型花岗岩平衡的是石榴石,与南岭型花岗岩平衡的是富钙的斜长石。文中指出,加强实验岩石学研究,将年代学和地球化学研究密切结合起来是深化花岗岩研究的关键。     

内蒙古西拉沐伦成矿带碾子沟钼矿床成矿流体地球化学特征

碾子沟钼矿床是内蒙古西拉沐伦钼多金属成矿带中石英脉型钼矿床的典型代表,矿体以石英大脉形式产于燕山期中粗粒黑云母二长花岗岩内,受断裂构造控制。流体包裹体研究发现包裹体均为气液两相,按照相比不同,可进一步分为WL型(5%～20%)和WV型(20%～50%)。Ⅰ阶段流体为低温(89.3～245.2℃)、中低盐度(2.07%～17.96%NaCleqv)流体;Ⅱ阶段流体具有中低温(134.4～458.8℃,峰值170℃～240℃)、中低盐度(0.53%～19.92%NaCleqv)特征;Ⅲ阶段流体为低温(134.9～202.4℃)、中低盐度(4.96%～14.97%NaCleqv)流体。流体成分均以H2O为主(96.1mol%),含少量挥发份CO2、N2、CH4、C2H6、Ar、H2S,阳离子以Na+为主,阴离子以SO42-、Cl-为主,属NaCl-H2O体系。各阶段成矿热液氢、氧同位素特征为:δ18OH2O介于-5.75‰～-1.90‰、δD介于-128.821‰～-109.234‰,说明成矿流体是岩浆热液与古大气降水混合而成。开放的断裂体系为流体混合创造了条件,流体的混合作用是造成碾子沟辉钼矿沉淀成矿的主要原因。这与斑岩型钼矿床的高盐度流体以及以沸腾为主的矿石沉淀机制具有显著区别。     

Variations in crustal structure on the East Pacific Rise crest: A travel time inversion approach

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.     

The influence of convection electric fields on thermal proton outflow from the ionosphere

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.     

Ionospheric measurements from the ESRO-4 satellite

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.