On the source region of flux transfer events

We have examined the region of occurrence of flux transfer events for three distinct orientations of the interplanetary magnetic field: nearly horizontal in the solar magnetospheric equator, diagonally southward at 45° to the magnetospheric equator and nearly due south. For horizontal IMF conditions the FTE's occur in a horizontal band about ± 6 R_E wide. For diagonally southward IMF conditions, the FTE's occur in a diagonal swath about ± 6 R_E wide passing through the subsolar point. For duskward but nearly due southward IMF conditions, our observations reveal FTE's throughout the northern morning quadrant. These observations are consistent with a near equatorial source for flux transfer events and hence with component merging and not anti-parallel merging. These observations also help understand the energetic ion anisotropies seen in these events.     

Interpretation of 6 and 21 cm observations of Jupiter

Observations of Jupiter's radio emission were made at a frequency of 1412 MHz (21cm) in 1977 and at 4885 MHz (6cm) in 1978 using the Westerbork Synthesis Radio telescope in the Netherlands. The thermal disk temperatures at these wavelengths yield values of 320±20 K at 21 cm and 220±8 K at 6 cm. The first value requires an overabundance of ammonia by a factor of three with respect to the solar value, the second one is in agreement with the value expected for a convective model atmosphere with solar abundances for all chemical elements. The data at this wavelength however show no or very little limb darkening on the planet, indicating that there is a layered rather than a uniformly mixed atmosphere. A sudden increase in the ammonia abundance by a factor of about three below the 210–220 K level is proposed to explain this fact and also both derived disk temperatures.     

Electrostatic discharges in Saturn's B-ring

The Voyager observations of electrical discharges in Saturn's rings strongly support earlier speculations on the role played by electrostatics, magnetic fields, and lightning phenomena in the primitive solar system. They also suggest conditions then by direct analogy rather than by extrapolating backwards through time from conditions now. The observed discharges show a pronounced 10^h periodicity, which suggests a source in Keplerian orbit at 1.80 ± 0.01 Saturn radii (1 R_S = 60,330 km). In that region, the B ring is thicker than optical depth 1.8 for about 5,000 km. At 1.805 ± 0.001 Saturn radii, however, the ring is virtually transparent for a gap of width 200 m. We conclude that a small satellite orbits Saturn at that radius and clears the gap. The gap edges must prevent diffusive filling of the gap by fine material which is especially abundant at this position in the rings and would otherwise destroy the gap in minutes. The discharges represent the satellite's interaction with the outer edge of the gap. Spoke formation may involve the interaction of ring material in the vicinity of the gap.     

Preliminary results of a meteorological payload being developed by IITM

A meteorological rocket payload developed at the Indian Institute of Tropical Meteorology (IITM) using thermistor as a temperature sensor was flight tested on RH-200 rocket at Thumba (08° 32'N, 76° 52'E), India, during February/April 1982 on four occasions. The corrected data obtained with this payload are compared with Russian rocket, M-100, data. The temperature profile obtained with IITM payload is warmer above 45-km, as compared with M-100 temperature profile, on all occasions. Meridional and zonal winds also agree up to 45-km level. Temperature records show a wave pattern varying in amplitude and frequency in the 20 to 45-km range.     

Voyager photopolarimeter observations of Saturn and Titan

The Voyager 2 photopolarimeter experiment observed the intensity and polarization of scattered sunlight from the atmospheres of Saturn and Titan in the near-UV at 2640 Å and in the near-IR at 7500 Å. Measurements of Saturn's limb brightening and polarization at several phase angles up to 70° indicate that a significant optical depth of UV absorbers are present in the top 100 mbar of Saturn's atmosphere in the Equatorial Zone and north polar region, and possibly at other latitudes as well. UV absorbers are prominent in polar regions, suggesting that charged particle precipitation from the magnetosphere may be important in their formation.The whole-body polarization of Titan is strongly positive in both the UV and near IR. If spherical particles are responsible for the polarization, no single size distribution or refractive index can account for the polarization at both wavelengths. The model atmosphere proposed by Tomasko and Smith [1], characterized by a gradient in particle size with altitude, seems capable of explaining the Voyager observations. If non-spherical particles predominate, the Voyager observations place important constraints on their scattering properties.     

Neutral temperatures from Thomson scatter measurements: Comparisons with the CIRA(1972)

Neutral exospheric and lower thermospheric (100–130 km) temperatures from Thomson scatter measurements at Millstone Hill (42°N) are compared with CIRA temperatures with a view towards identifying deficiencies in the CIRA and recommending revisions. CIRA models the observed diurnal mean temperatures (T₀) to within 10% over a wide range of solar conditions (75? F_10.7 ? 250), but consistently underestimates the diurnal temperatures with maximum deviations approaching 50% of observed amplitudes (180–240 K) at solar maximum (1200 K ? T₀ ? 1400 K). The observed semidiurnal amplitudes, which lie in the range of 20K–80K, are always underestimated and frequently by more than 50%. In the lower thermosphere, tidal oscillations of temperature of order 20K–40K occur which are not modelled by CIRA. In addition, an analysis of exospheric temperatures at Millstone Hill during a magnetic disturbance indicates a response within 1–2 hours from storm onset, whereas CIRA assumes a 6.7 hour delay. Although some of these deficiences are addressed by the more recent MSIS model, there exists a sufficient data base to recommend several additional revisions to the CIRA temperatures at this time.     

基于“嫦娥2号”CELMS数据的冯·卡门撞击坑微波辐射特性

冯·卡门（Von Kármán）撞击坑位于月球背面的SPA盆地西北部,切穿了浅层月壳,具有异常的矿物成分分布。基于微波辐射计数据的月壤微波辐射特性分析,对月球热演化和岩浆演化研究具有重要的参考价值。本研究基于“嫦娥2号”卫星微波辐射计数据,采用时角分析、双线性插值方法,生成了研究区域的亮温（T_B）图和亮温差（dT_B）图像;结合Arcgis软件,叠加地质图,并结合成分、地形图,研究了Von Kármán撞击坑微波辐射特性。研究结果表明：研究区北部出现高T_B异常,初步判定为下垫面温度较高;研究区南部出现与钛铁矿（FeO+TiO₂）含量分布相对应的亮温表现;结合研究区的微波辐射特性,重新进行了冯·卡门撞击坑地质解译;根据冯·卡门撞击坑的亮温表现,建议北部为着陆区重点选择区,其次为南部和西部。     

TIMED/SABER与AURA/MLS临近空间探测温度数据比较

利用AURA/MLS数据（V4.2）和TIMED/SABER数据（V2.0）对20~92km高度的大气温度进行比较分析,计算AURA/MLS数据与TIMED/SABER数据的温度绝对偏差,并分析平均温度偏差在不同季节中随经度、纬度和高度的变化特征.结果表明:20~80km高度的平均温度偏差在±6K以内,相对偏差在3%以内;80~90km高度平均温度偏差减小至-10K以下,相对偏差在9%以内.中低纬度地区平均温度偏差廓线的变化趋势一致,从20km高度的-3K左右的负偏差逐渐增加,在45~50km高度的平流层顶处有较明显的3K左右的正偏差峰值.平均温度偏差随纬度变化明显,随经度变化很小.研究结果可为卫星数据的应用提供参考依据.      

Saturn's equatorial haze

We have measured the amount of Raman scattering in Saturn's equatorial zone and polar regions near the central meridian at the wavelengths of the H and K Ca II solar lines, 3934 Å and 3969 Å. Approximately 2.1% of the sunlight in this wavelength range is Raman scattered out of this range in Saturn's equatorial zone. Modeling the aerosol particle distribution as a clear, Rayleigh- and Raman-scattering gas over a dense haze yields an H₂ column abundance of about 40 km-Amagats. Comparison with results obtained by Pioneer 11 suggests that either the equatorial haze was 2.5 times deeper at the time of these observations (May, 1981) than at the time of the Pioneer 11 flyby (Sept., 1979); or the haze particles are much more strongly polarizing in blue light than they are in red light.     

Far-infrared and submillimeter survey of the galactic center and nearby galactic plane

Maps are presented with 12′ resolution of the Galactic Center and adjacent galactic plane, from ?^II = 359° to ?^II = 5°. The data were obtained with the Steward Observatory cryogenically-cooled, balloon-borne telescope. The data are from channels filtered for a bandpass of 70 μm < γ < 110 μm and for a longpass of γ > 80 μm. For the typical effective temperature of 25 K of a galactic HII region at this spatial resolution, the effective wavelength of the channels are 93 μ and 145 μm. Continuous emission is mapped along the galactic plane in both wavelengths. There are two contrasts between the immediate vicinity of SgrA (?^π < 1°) and the galactic plane in general. Firstly, for ?^π > 1° the galactic plane narrows dramatically at 93 μm, while retaining its width at 145 μm. Secondly, the individual sources at ?^π > 1° (which we associate with HII regions) have greater peak brightness in the 145 μm channel than the 93 μm channel, while SgrA hasapproximately equal peak brightness in each. The maps demonstrate the importance of submillimeter wavelengths to galactic surveys.     

Comparison of cloud top heights measured by airborne Lidar and TIROS-N image data

The determination of the cloud top height by means of satelliteborne IR-radiometers requires the conversion of the measured radiance to an equivalent blackbody temperature and the assignment of this temperature to a geometrical height. The latter is associated with errors which add up easily to several kilometers. DFVLR did a case study to compare satellite derived cloud top heights with those from airborne Lidar measurements. The difference of the radiosonde temperature from the standard temperature profile results in a 1.8 km difference in cloud top height. The achievable accuracy using actual radiosonde temperatures is ± 0.4 km for optical thick clouds and much less for optical thin clouds.     

Pluto's atmospheric bulk near perihelion

The detection of CH₄ frost on Pluto's surface implies a significant atmosphere for Pluto. Although Pluto's mass is small, about 7% of Triton's mass, the rapid escape (“blowoff”) of gaseous CH₄ can be prevented by the presence of a heavy gas mixed with the CH₄. The resulting slow escape (“Jeans escape”) of CH₄ can be accomodated by sublimation of the surface CH₄ frost so that an atmosphere exists in the steady state. A heavier gas must exist, otherwise the CH₄ frost would have sublimated away long ago because of solar heat and rapid blowoff of gaseous CH₄. Pluto is currently near perihelion where the CH₄ component of the atmosphere may be 500 times denser than at apehelion. Significant seasonal changes in the atmospheric bulk are therefore possible. Currently, the CH₄ column abundance on Pluto's sunlit hemisphere is on the order of 1 m-Amagat. The abundance of the heavier gas should be at least an order of magnitude greater but is uncertain.     

Effect of gravity on coupled convective and interfacial instabilities during directional solidification

We investigate the role of gravity in a linear stability analysis of the onset of coupled convective and morphological instabilities during directional solidification at constant velocity of a dilute alloy of tin in lead. For solidification vertically upwards, the temperature gradient alone would cause a negative density gradient and the solute gradient alone would cause a positive density gradient. Two types of instability are found, a convective type that occurs for long wavelengths and a morphological type that occurs for short wavelengths. In general, these are coupled but the morphological instabilities are practically independent of gravity and thus correspond to the predictions of previous morphological stability theory in which density changes and convection are neglected. The convective instabilities depend strongly on gravity; for a growth velocity of V = 1 μm/s and a temperature gradient in the liquid of G_L = 200 K/cm, the critical concentrations for convective instabilities are 3.1 × 10^?4, 3.1 × 10^?2 and 2.39 wt. % for g_e = 980 cm/s², 10^?4 g_e and 10^?6 g_e, respectively. For low velocities, the convective instabilities occur at much lower solute concentrations than the morphological instabilities whereas at high velocities, the reverse is true. At intermediate velocities where the changeover takes place, there are oscillitory instabilities of mixed character whose periods range from 60 s at g_e to 6 × 10⁴ s at 10^?6 g_e.     

Some aspects of temperature sounding of the atmosphere

Based on measurements with the interferometer spectrometer SI-1 on board of Meteor satellites the following problems are investigated: the systematic effect of the spectral response function in deriving effective radiation temperatures; the selection of ‘optimal’ spectral channels within the 15 μm region, and effects of additional molecular absorbers on the determination of the temperature profile. It can be shown that using broad-band window channels (half width ?20cm^?1) the derived surface temperature is significantly different from the surface temperature derived from narrow spectral band channels (e.g. for the HIRS window channel 8 this difference is about 1° C). Simulations of some combinations of spectral channels including one proposed as an optimal approach show no significant difference in the derived temperature profile. Neglecting the ozone absorption of the 14.1 μm band leads to a change in radiance of about 1.5 mW/m²sr cm^?1 and to a systematic error of the derived temperature of about ?2° C in the troposphere.     

镱原子二级冷却的实验研究

介绍了镱原子光钟中的二级冷却实验过程。在一级冷却的基础上,将冷镱原子成功转移至555.8nm磁光阱中。用时间飞行法测量174Yb超冷原子的温度约为100μK,171Yb超冷原子的温度约为30μK。     

瑞利激光雷达反演中层大气温度算法

瑞利激光雷达是探测中层大气温度的重要设备,具有高时空分辨率且不存在探测盲区的优点.为充分利用激光雷达探测到的原始数据,改进了传统的Chanin-Haunchecorne方法,采用由均匀搜索生成温度初值的方式反演大气温度.位于北京延庆（40.3°N,116.2°E）的瑞利激光雷达具有589nm和532nm两个通道,将589nm通道用于计算,532nm通道作为参考.在150~250K区间等间隔选取多个温度初值,利用589nm通道反演60~70km高度范围内的大气温度廓线和大气密度廓线,利用参考密度廓线选取准确的温度初值,反演得到准确的大气温度廓线.将589nm通道和532nm通道反演的温度廓线相比较,发现二者具有较高的一致性.改进后的方法有效利用了信噪比较差的光信号,使589nm通道的温度探测上限从60km提高到70km.      

The problem of indirect sounding of high clouds

Remote sounding of high cloud top temperatures by passive methods is a difficult venture due to the semitransparency of the clouds. Window channel measurements often overestimate the cloud top temperature. In this study it is experimentally shown and supported by theoretical considerations that water vapor channels, which are originally intended to sense the high tropospheric water vapor content, are more suitable than window channels. In addition, it is shown that measurements in the H₂O rotational band are superior to 6.3 μm channels due to higher intensity of the outgoing radiation and less contribution by scattering by cloud particles.     

Global MGS TES data and Mars-GRAM validation

Mars Global Reference Atmospheric Model (Mars-GRAM 2001) is an engineering-level Mars atmosphere model widely used for many Mars mission applications. From 0 to 80 km, it is based on NASA Ames Mars General Circulation Model (MGCM), while above 80 km it is based on University of Michigan Mars Thermospheric General Circulation Model. Mars-GRAM 2001 and MGCM use surface topography from Mars Global Surveyor Mars Orbiter Laser Altimeter (MOLA). Validation studies are described comparing Mars-GRAM with a global summary data set of Mars Global Surveyor Thermal Emission Spectrometer (TES) data. TES averages and standard deviations were assembled from binned TES data which covered surface to ∼40 km, over more than a full Mars year (February 1999–June 2001, just before start of a Mars global dust storm). TES data were binned in 10° × 10° latitude–longitude bins (36 longitude bins, centered at 5°–355°, by 18 latitude bins, centered at −85° to +85°), and 12 seasonal bins (based on 30° increments of L_s angle). Bin averages and standard deviations were assembled at 23 data levels (temperature at 21 pressure levels, plus surface temperature and surface pressure). Two time-of-day bins were used: local time near 2 or 14 h. Two dust optical depth bins were used: infrared optical depth, either less than or greater than 0.25 (which corresponds to visible optical depth less than or greater than about 0.5). For interests in aerocapture and precision entry and landing, comparisons focused on atmospheric density. TES densities versus height were computed from TES temperature versus pressure, using assumptions of perfect gas law and hydrostatics. Mars-GRAM validation studies used density ratio (TES/Mars-GRAM) evaluated at data bin center points in space and time. Observed average TES/Mars-GRAM density ratios were generally 1 ± 0.05, except at high altitudes (15–30 km, depending on season) and high latitudes (>45°N), or at most altitudes in the southern hemisphere at L_s ∼ 90° and 180°. Compared to TES averages for a given latitude and season, TES data had average density standard deviation about the mean of ∼2.5% for all data, or ∼1–4%, depending on time of day and dust optical depth. Average standard deviation of TES/Mars-GRAM density ratio was 8.9% for local time 2 h and 7.1% for local time 14 h. Thus standard deviation of observed TES/Mars-GRAM density ratio, evaluated at matching positions and times, is about three times the standard deviation of TES data about the TES mean value at a given position and season.     

Planetary rings: 2–23 centuries of nearly total ignorance, 4 years of information explosion

Saturn lies at nearly twice Jupiter's distance from the Sun and nearly all parts of its system are characterized by much smaller scales than those which are important in the case of Jupiter. This appears in the structures of the planet's atmosphere, in the sizes of classical satellites other than Titan vis-à-vis those of the Galilean satellites, in the plethora of small Saturnian satellites, especially Lagrangian co-orbiters, in the structure of Saturn's F-Ring as contrasted with that of Jupiter's Ring and finally in the highly structured detail in Saturn's Rings, much finer than seriously considered in past theoretical discussions. Uranus' Rings were unknown until five years ago. The discovery and observation of these rings have revived contributions to theory originally intended for application to Saturn's Rings. Models have also been generated for eccentric rings for application to Uranus' Rings which also apply to those of Saturn. These two classes of model are reviewed in the present paper along with the first tentative steps made down the road to unravelling the complexity of Saturn's Rings.     

Mapping the earth's magnetic and gravity fields from space: Current status and future prospects

Orbital potential field measurements are sensitive to regional variations in earth density and magnetization that occur over scales of a few hundred kilometers or greater. Global field models currently available are able to distinguish gravity variations of ±5 milligal over distances of ～1,000 km and magnetic variations of ±6 gamma over distances of ～300 km at the earth's surface. Regional variations in field strength have been detected in orbital measurements that are not apparent in higher resolution, low altitude surveys. NASA is presently studying a spacecraft mission known as GRAVSAT/MAGSAT, which would be the first satellite mission to perform a simultaneous survey of the earth's gravity and magnetic fields at low orbital altitudes. GRAVSAT/MAGSAT has been proposed for launch during the latter nineteen-eighties, and it would measure gravity field strength to an accuracy of 1 milligal and magnetic field strength to an accuracy of 2 gamma (scalar)/5 gamma (vector components) over a distance of roughly 100 km. Even greater improvements in the accuracy and spatial resolution of orbital surveys are anticipated during the nineteen-nineties with the development of potential field gradiometers and a tethered satellite system that can be deployed from the Space Shuttle to altitudes of 120 km above the earth's surface.