Voyager radio science observations of neptune and triton

The Voyager 2 encounter with the Neptune system included radio science investigations of the masses and densities of Neptune and Triton, the low-order gravitational harmonics of Neptune, the vertical structures of the atmospheres and ionospheres of Neptune and Triton, the composition of the atmosphere of Neptune, and characteristics of ring material. Demanding experimental requirements were met successfully, and study of the large store of collected data has begun. The initial search of the data revealed no detectable effects of ring material with optical depth tau [unknown] 0.01. Preliminary representative results include the following: 1.0243 x 10(26) and 2.141 x 10(22) kilograms for the masses of Neptune and Triton; 1640 and 2054 kilograms per cubic meter for their respective densities; 1355 +/- 7 kilometers, provisionally, for the radius of Triton; and J(2) = 3411 +/- 10(x 10(-6)) and J(4) = -26(+12)(-20)(x10(-6)) for Neptune's gravity field (J>(2) and J(4) are harmonic coefficients of the gravity field). The equatorial and polar radii of Neptune are 24,764 +/- 20 and 24,340 +/- 30 kllometers, respectively, at the 10(5)-pascal (1 bar) pressure level. Neptune's atmosphere was probed to a pressure level of about 5 x 10(5) pascals, and effects of a methane cloud region and probable ammonia absorption below the cloud are evident in the data. Results for the mixing ratios of helium and ammonia are still being investigated; the methane abundance below the clouds is at least 1 percent by volume. Derived temperature-pressure profiles to 1.2 x 10(5) pascals and 78 kelvins (K) show a lapse rate corresponding to "frozen" equilibrium of the para- and ortho-hydrogen states. Neptune's ionosphere exhibits an extended topside at a temperature of 950 +/- 160 K if H(+) is the dominant ion, and narrow ionization layers of the type previously seen at the other three giant planets. Triton has a dense ionosphere with a peak electron concentration of 46 x 10(9) per cubic meter at an altitude of 340 kilometers measured during occultation egress. Its topside plasma temperature is about 80 +/- 16 K if N(2)(+) is the principal ion. The tenuous neutral atmosphere of Triton produced distinct signatures in the occultation data; however, the accuracy of the measurements is limited by uncertainties in the frequency of the spacecraft reference oscillator. Preliminary values for the surface pressure of 1.6 +/- 0.3 pascals and an equivalent isothermal temperature of 48 +/- 5 K are suggested, on the assumption that molecular nitrogen dominates the atmosphere. The radio data may be showing the effects of a thermal inversion near the surface; this and other evidence imply that the Triton atmosphere is controlled by vapor-pressure equilibrium with surface ices, at a temperature of 38 K and a methane mixing ratio of about 10(-4).     

Ultraviolet spectrometer observations of neptune and triton

Results from the occultation of the sun by Neptune imply a temperature of 750 +/- 150 kelvins in the upper levels of the atmosphere (composed mostly of atomic and molecular hydrogen) and define the distributions of methane, acetylene, and ethane at lower levels. The ultraviolet spectrum of the sunlit atmosphere of Neptune resembles the spectra of the Jupiter, Saturn, and Uranus atmospheres in that it is dominated by the emissions of H Lyman alpha (340 +/- 20 rayleighs) and molecular hydrogen. The extreme ultraviolet emissions in the range from 800 to 1100 angstroms at the four planets visited by Voyager scale approximately as the inverse square of their heliocentric distances. Weak auroral emissions have been tentatively identified on the night side of Neptune. Airglow and occultation observations of Triton's atmosphere show that it is composed mainly of molecular nitrogen, with a trace of methane near the surface. The temperature of Triton's upper atmosphere is 95 +/- 5 kelvins, and the surface pressure is roughly 14 microbars.     

Energetic charged particles in the magnetosphere of neptune

The Voyager 2 cosmic ray system (CRS) measured significant fluxes of energetic [>/=1 megaelectron volt (MeV)] trapped electrons and protons in the magnetosphere of Neptune. The intensities are maximum near a magnetic L shell of 7, decreasing closer to the planet because of absorption by satellites and rings. In the region of the inner satellites of Neptune, the radiation belts have a complicated structure, which provides some constraints on the magnetic field geometry of the inner magnetosphere. Electron phase-space densities have a positive radial gradient, indicating that they diffuse inward from a source in the outer magnetosphere. Electron spectra from 1 to 5 MeV are generally well represented by power laws with indices near 6, which harden in the region of peak flux to power law indices of 4 to 5. Protons have significantly lower fluxes than electrons throughout the magnetosphere, with large anisotropies due to radial intensity gradients. The radiation belts resemble those of Uranus to the extent allowed by the different locations of the satellites, which limit the flux at each planet.     

元江干热河谷太阳辐射各分量及反照率变化特征

为了探讨干热河谷太阳辐射的特征,本文利用元江干热河谷稀树灌草丛通量塔上连续2年(2013年5月至2015年4月)辐射数据,对元江干热河谷稀树灌草丛植被林冠上太阳辐射(总辐射(Q)、反射辐射(Qα)、有效辐射(I)、净辐射(Rn))的日变化、季节和年变化特征进行分析,探讨了反照率(α)和I变化特征及其原因。结果表明: 该区域Q、Qα、I、Rn的年均辐射值分别为6 210.2、807.9、1 822.9、3 578.7 MJ/(m2·a)。雨季各辐射总量占年总量比例分别为52.9%、56.3%、39.1%、59.2%,除雨季I占全年的比例小于干季外,其他3个辐射分量占全年的比例均是干季雨季。α由于受雨季叶面积指数(LAI)增大和林冠郁闭度增加的影响,其季节变化特征表现为干季雨季,这是生态系统为缓解该区域尖锐的水热矛盾而长期进化的结果。Qα、I和Rn年分配率分别为13.0%、29.8%、56.9%,其中Qα和Rn分配率的季节变化均表现为干季雨季,而I的分配率特征与Qα和Rn的相反。干季I分配率的增加降低了地面和林冠温度,减少了生态系统水分流失,削弱了研究区域干季时水分的胁迫效应,避免了森林植被因水力结构破坏而引发的碳饥饿所导致的死亡,有利于元江干热河谷稀树灌草丛植被在干季生存和维持该生态系统平衡。由于元江干热河谷Q和Rn都较大且该地区降雨少,故人类活动及气候变化更容易影响该地区的生态系统平衡。      

Dynamic variations at the base of the solar convection zone

We have detected changes in the rotation of the sun near the base of its convective envelope, including a prominent variation with a period of 1.3 years at low latitudes. Such helioseismic probing of the deep solar interior has been enabled by nearly continuous observation of its oscillation modes with two complementary experiments. Inversion of the global-mode frequency splittings reveals that the largest temporal changes in the angular velocity Omega are of the order of 6 nanohertz and occur above and below the tachocline that separates the sun's differentially rotating convection zone (outer 30% by radius) from the nearly uniformly rotating deeper radiative interior beneath. Such changes are most pronounced near the equator and at high latitudes and are a substantial fraction of the average 30-nanohertz difference in Omega with radius across the tachocline at the equator. The results indicate variations of rotation close to the presumed site of the solar dynamo, which may generate the 22-year cycles of magnetic activity.     

早期营养对免疫系统的长期调节作用

出生前后的早期营养对动物免疫系统的发育和功能较成年期更为关键，而且早期营养与随后疾病的发生有一定关系。当营养不良时，胎儿或初生动物代谢功能的可塑性使得它们能够适应营养不良而存活，这种适应反应通常表现为生长或淋巴器官发育迟缓和免疫能力降低，而这些表现既使在随后营养条件改善的情况下仍然可以继续保持，早期营养因而可以“预设”动物的免疫系统。为数不多的试验研究表明，断奶后短期蛋白质补饲可以增强绵羊对消化道寄生线虫的长期抵抗力，证明了早期营养对家畜免疫力的“预设”效应，但在早期营养可满足动物维持需要的情况下，这种效应可能不复存在。     

Long-term modulation of electrical synapses in the mammalian thalamus

Electrical synapses are common between inhibitory neurons in the mammalian thalamus and neocortex. Synaptic modulation, which allows flexibility of communication between neurons, has been studied extensively at chemical synapses, but modulation of electrical synapses in the mammalian brain has barely been examined. We found that the activation of metabotropic glutamate receptors, via endogenous neurotransmitter or by agonist, causes long-term reduction of electrical synapse strength between the inhibitory neurons of the rat thalamic reticular nucleus.     

Latitudinal and longitudinal oscillations of cloud features on neptune

Voyager observations suggest that three of Neptune's major cloud features oscillate in latitude by 2 degrees to 4 degrees and that two of them simultaneously oscillate in longitude by 7.8 degrees and 98 degrees about their mean drift longitudes. The observations define most convincingly the two orthogonal oscillations of the second dark spot (near 53 degrees south). These oscillations have similar periods near 800 hours and approximately satisfy a simple advective model in which a latitudinal oscillation produces a phase-shifted longitudinal oscillation proportional to the local wind shear. The latitudinal motion of the Great Dark Spot can be fit with an oscillation period of about 2550 hours, whereas its dominant longitudinal motion, if oscillatory at all, has such a long period that it is not well constrained by the Voyager data.     

Long-term change in the nitrogen cycle of tropical forests

Deposition of reactive nitrogen (N) from human activities has large effects on temperate forests where low natural N availability limits productivity but is not known to affect tropical forests where natural N availability is often much greater. Leaf N and the ratio of N isotopes (δ(15)N) increased substantially in a moist forest in Panama between ~1968 and 2007, as did tree-ring δ(15)N in a dry forest in Thailand over the past century. A decade of fertilization of a nearby Panamanian forest with N caused similar increases in leaf N and δ(15)N. Therefore, our results indicate regional increases in N availability due to anthropogenic N deposition. Atmospheric nitrogen dioxide measurements and increased emissions of anthropogenic reactive N over tropical land areas suggest that these changes are widespread in tropical forests.     

Length of the solar cycle: an indicator of solar activity closely associated with climate

It has recently been suggested that the solar irradiance has varied in phase with the 80- to 90-year period represented by the envelope of the 11-year sunspot cycle and that this variation is causing a significant part of the changes in the global temperature. This interpretation has been criticized for statistical reasons and because there are no observations that indicate significant changes in the solar irradiance. A set of data that supports the suggestion of a direct influence of solar activity on global climate is the variation of the solar cycle length. This record closely matches the long-term variations of the Northern Hemisphere land air temperature during the past 130 years.     

Ozone and temperature trends associated with the 11-year solar cycle

Evidence is presented which suggests that trends in the ozone concentration and stratospheric temperature, reported between the early 1960's and 1976, are to a large extent due to solar ultraviolet flux variability associated with the 11-year solar cycle. Radiative-convective-photochemical simulations of ozone and temperature variations have been made with a solar ultraviolet flux variability model. Results for temperatures and ozone concentrations, when compared with published data, show good agreement.     

Isotopic evidence for variations in the marine calcium cycle over the Cenozoic

Significant variations in the isotopic composition of marine calcium have occurred over the last 80 million years. These variations reflect deviations in the balance between inputs of calcium to the ocean from weathering and outputs due to carbonate sedimentation, processes that are important in controlling the concentration of carbon dioxide in the atmosphere and, hence, global climate. The calcium isotopic ratio of paleo-seawater is an indicator of past changes in atmospheric carbon dioxide when coupled with determinations of paleo-pH.     

Constraints on the diameter and albedo of 2060 chiron

Asteroid 2060 Chiron is the largest known object exhibiting cometary activity. Radiometric observations made in 1983 from a ground-based telescope and the Infrared Astronomical Satellite are used to examine the limits on Chiron's diameter and albedo. It is argued that Chiron's surface temperature distribution at that time is best described by an "isothermal latitude" or "rapid-rotator" model. Consequently, Chiron has a maximum diameter of 372 kilometers and a minimum geometric albedo of 2.7%. This is much bigger and darker than previous estimates, and suggests that gravity may play a significant role in the evolution of gas and dust emissions. It is also found that for large obliquities, surface temperatures can vary dramatically on time scales of a decade, and that such geometry may play a critical role in explaining Chiron's observed photometric behavior since its discovery in 1977.     

A model of solar luminosity modulation by magnetic activity between 1954 and 1984

A simple model based on the changes in excess radiation from bright magnetic faculae and on changes in reduced radiation from dark spots is remarkably successful in matching the slow variations of total solar irradiance measured simultaneously by the ERB and ACRIM satellite radiometers between 1981 and 1984. This model was extended back to 1954 to reconstruct the modulation of irradiance by magnetic activity during the past three 11-year solar cycles. The model predicts that the sun is consistently brighter at activity maximum than at minimum. The 0.07 percent brightening at the peak of the last cycle in 1980 was more pronounced than the brightenings found for either of the two previous cycles, even though cycle 19, which peaked around 1957, had the largest sunspot number amplitude in the history of reliable sunspot records.     

Oxygen isotope variations at the margin of a CAI records circulation within the solar nebula

Micrometer-scale analyses of a calcium-, aluminum-rich inclusion (CAI) and the characteristic mineral bands mantling the CAI reveal that the outer parts of this primitive object have a large range of oxygen isotope compositions. The variations are systematic; the relative abundance of (16)O first decreases toward the CAI margin, approaching a planetary-like isotopic composition, then shifts to extremely (16)O-rich compositions through the surrounding rim. The variability implies that CAIs probably formed from several oxygen reservoirs. The observations support early and short-lived fluctuations of the environment in which CAIs formed, either because of transport of the CAIs themselves to distinct regions of the solar nebula or because of varying gas composition near the proto-Sun.     

Long-term spatial and temporal variations of soil organic carbon in the Handan region in Northern China

We carried out a long-term study and a systematic analysis on the spatial and temporal variations of the soil organic carbon contents in the counties of Handan Prefecture in Hebei Province, on the North China Plains. The analysis was based on the data collected in soil surveys conducted in 1980, 1993 and 2003, as well as the data from specific investigations using GIS and GPS receivers. The soil organic carbon content was higher in the western mountainous region than in the eastern plain region in 1980, and the difference in the average values was 17.745 t·hm⁻². The soil organic carbon content was influenced by natural factors, such as climate and rainfall. In 1993, the soil organic carbon content showed an upward trend in the eastern plain region and a downward trend in the western mountainous region. The difference in the average values was 16.641 t·hm⁻². The changing trend reflected the changes in farming practices where traditional farming was changed into modern farming gradually by increasing farming investment and output of grains. In 2003, the soil organic carbon content was high on the whole, and the difference in the average values was 16.984 t·hm⁻², where the influence of human factors played an important role. In Cixian, Linzhang, Wuan and Handan counties, the increased value of soil organic carbon in the cultivated land exceeded 3.915 t·hm⁻² due to the advocated application of straw and farmyard manure in these counties, but in Weixian, Jize and Quzhou counties, the soil organic carbon content was maintained or showed a slight decrease (−0.008-−1.727 t·hm⁻²). To increase carbon sequestration in soil, adoption of conservation tillage to increase soil organic carbon storage in the soil is recommended.     

Permanent lunar surface magnetism and its deflection of the solar wind

Magnetic compressions intermittently observed outside the lunar wake in the solar wind may be limb shocks caused by the presence of local regions of permanent magnetism on the lunar limb. Observable compression would be due to regions of length scale (radius) at least as great as several tens of kilometers and field strength greater, similar 10 gammas. Thousands of such regions might exist on the lunar surface. The steady magnetic field measured at the Apollo 12 site probably has length scale less, similar 10 kilometers and probably does not produce an observable limb shock.     

Magnetic field of jupiter and its interaction with the solar wind

Jupiter's magnetic field and its interaction with the magnetized solar wind were observed with the Pioneer 10 vector helium magnetometer. The magnetic dipole is directed opposite to that of the earth with a moment of 4.0 gauss R(J)(3) (R(J), Jupiter radius), and an inclination of 15 degrees lying in a system III meridian of 230 degrees . The dipole is offset about 0.1 R(J) north of the equatorial plane and about 0.2 R(J) toward longitude 170 degrees . There is severe stretching of the planetary field parallel to the equator throughout the outer magnetosphere, accompanied by a systematic departure from meridian planes. The field configuration implies substantial plasma effects inside the magnetosphere, such as thermal pressure, centrifugal forces, and differential rotation. As at the earth, the outer boundary is thin, nor diffuse, and there is a detached bow shock.