共查询到20条相似文献，搜索用时 578 毫秒
1.
Gladstone GR Stern SA Slater DC Versteeg M Davis MW Retherford KD Young LA Steffl AJ Throop H Parker JW Weaver HA Cheng AF Orton GS Clarke JT Nichols JD 《Science (New York, N.Y.)》2007,318(5848):229-231
Observations of Jupiter's nightside airglow (nightglow) and aurora obtained during the flyby of the New Horizons spacecraft show an unexpected lack of ultraviolet nightglow emissions, in contrast to the case during the Voyager flybys in 1979. The flux and average energy of precipitating electrons generally decrease with increasing local time across the nightside, consistent with a possible source region along the dusk flank of Jupiter's magnetosphere. Visible emissions associated with the interaction of Jupiter and its satellite Io extend to a surprisingly high altitude, indicating localized low-energy electron precipitation. These results indicate that the interaction between Jupiter's upper atmosphere and near-space environment is variable and poorly understood; extensive observations of the day side are no guide to what goes on at night. 相似文献
2.
Simpson JA Anglin JD Balogh A Burrows JR Cowley SW Ferrando P Heber B Hynds RJ Kunow H Marsden RG McKibben RB Müller-Mellin R Page DE Raviart A Sanderson TR Staines K Wenzel KP Wilson MD Zhang M 《Science (New York, N.Y.)》1992,257(5076):1543-1550
The Ulysses spacecraft made the first exploration of the region of Jupiter's magnetosphere at high Jovigraphic latitudes ( approximately 37 degrees south) on the dusk side and reached higher magnetic latitudes ( approximately 49 degrees north) on the day side than any previous mission to Jupiter. The cosmic and solar particle investigations (COSPIN) instrumentation achieved a remarkably well integrated set of observations of energetic charged particles in the energy ranges of approximately 1 to 170 megaelectron volts for electrons and 0.3 to 20 megaelectron volts for protons and heavier nuclei. The new findings include (i) an apparent polar cap region in the northern hemisphere in which energetic charged particles following Jovian magnetic field lines may have direct access to the interplanetary medium, (ii) high-energy electron bursts (rise times approximately 17 megaelectron volts) on the dusk side that are apparently associated with field-aligned currents and radio burst emissions, (iii) persistence of the global 10-hour relativistic electron "clock" phenomenon throughout Jupiter's magnetosphere, (iv) on the basis of charged-particle measurements, apparent dragging of magnetic field lines at large radii in the dusk sector toward the tail, and (v) consistent outflow of megaelectron volt electrons and large-scale departures from corotation for nucleons. 相似文献
3.
Pioneer 11 has made the first exploration of the magnetosphere and trapped radiation belts of Saturn. Saturn's magnetosphere is intermediate in size between Earth's and Jupiter's, with trapped particle intensities comparable to Earth's. The outer region of Saturn's magnetosphere contains lower energy radiation and is variable with time; the inner region contains higher energy particles. The pitch angle distributions show a remarkable variety of field-aligned and locally mirroring configurations. The moons and especially the rings of Saturn are effective absorbers of trapped particles; underneath the rings, the trapped radiation is completely absorbed. We confirm the discovery of a new ring, called the F ring, a new division, the Pioneer division, and a moon, called 1979 S 2. The latter has probably been seen from Earth. There may be evidence for more bodies like 1979 S 2, but at this stage the interpretation of the data is ambiguous. Using particle diffusion rates, we estimate that the cross-sectional area of the F ring is > 7 x 10(13) square centimeters and that the opacity is > 10(-5). Cosmic-ray albedo neutron decay should be looked into as a source of energetic particles in the inner magnetosphere of Saturn. 相似文献
4.
Waite JH Gladstone GR Franke K Lewis WS Fabian AC Brandt WN Na C Haberl F Clarke JT Hurley KC Sommer M Bolton S 《Science (New York, N.Y.)》1995,268(5217):1598-1601
R?ntgensatellit (ROSAT) observations made shortly before and during the collision of comet Shoemaker-Levy 9 with Jupiter show enhanced x-ray emissions from the planet's northern high latitudes. These emissions, which occur at System III longitudes where intensity enhancements have previously been observed in Jupiter's ultraviolet aurora, appear to be associated with the comet fragment impacts in Jupiter's southern hemisphere and may represent brightenings of the jovian x-ray aurora caused either by the fragment impacts themselves or by the passage of the fragments and associated dust clouds through Jupiter's inner magnetosphere. 相似文献
5.
HM Fischer E Pehlke G Wibberenz LJ Lanzerotti JD Mihalov 《Science (New York, N.Y.)》1996,272(5263):856-858
The energetic particles investigation carried by the Galileo probe measured the energy and angular distributions of the high-energy particles from near the orbit of Io to probe entry into the jovian atmosphere. Jupiter's inner radiation region had extremely large fluxes of energetic electrons and protons; intensities peaked at approximately2.2RJ (where RJ is the radius of Jupiter). Absorption of the measured particles was found near the outer edge of the bright dust ring. The instrument measured intense fluxes of high-energy helium ions (approximately62 megaelectron volts per nucleon) that peaked at approximately1.5RJ inside the bright dust ring. The abundances of all particle species decreased sharply at approximately1.35RJ; this decrease defines the innermost edge of the equatorial jovian radiation. 相似文献
6.
Teleconvection: remotely driven thermal convection in rotating stratified spherical layers 总被引：1，自引：0，他引：1
We report the discovery of a convective phenomenon found to occur in a rotating spherical system in which an inner convectively unstable fluid layer is bounded by a corotating outer convectively stable fluid layer. Although convection is thermally driven in the unstable interior, the resulting convective motions concentrate primarily in the stable outer region. This phenomenon, which we term teleconvection, suggests that fluid motions observed at the "surface" of a planet (such as Jupiter's alternating zonal winds) may be driven by an energy source located deep inside the planet. 相似文献
7.
McNutt RL Haggerty DK Hill ME Krimigis SM Livi S Ho GC Gurnee RS Mauk BH Mitchell DG Roelof EC McComas DJ Bagenal F Elliott HA Brown LE Kusterer M Vandegriff J Stern SA Weaver HA Spencer JR Moore JM 《Science (New York, N.Y.)》2007,318(5848):220-222
When the solar wind hits Jupiter's magnetic field, it creates a long magnetotail trailing behind the planet that channels material out of the Jupiter system. The New Horizons spacecraft traversed the length of the jovian magnetotail to >2500 jovian radii (RJ; 1 RJ identical with 71,400 kilometers), observing a high-temperature, multispecies population of energetic particles. Velocity dispersions, anisotropies, and compositional variation seen in the deep-tail (greater, similar 500 RJ) with a approximately 3-day periodicity are similar to variations seen closer to Jupiter in Galileo data. The signatures suggest plasma streaming away from the planet and injection sites in the near-tail region (approximately 200 to 400 RJ) that could be related to magnetic reconnection events. The tail structure remains coherent at least until it reaches the magnetosheath at 1655 RJ. 相似文献
8.
A Seiff DB Kirk TCD Knight LA Young FS Milos E Venkatapathy JD Mihalov RC Blanchard RE Young G Schubert 《Science (New York, N.Y.)》1997,276(5309):102-104
Temperatures in Jupiter's atmosphere derived from Galileo Probe deceleration data increase from 109 kelvin at the 175-millibar level to 900 ± 40 kelvin at 1 nanobar, consistent with Voyager remote sensing data. Wavelike oscillations are present at all levels. Vertical wavelengths are 10 to 25 kilometers in the deep isothermal layer, which extends from 12 to 0.003 millibars. Above the 0.003-millibar level, only 90- to 270- kilometer vertical wavelengths survive, suggesting dissipation of wave energy as the probable source of upper atmosphere heating. 相似文献
9.
Thorne RM 《Science (New York, N.Y.)》1977,195(4275):287-289
During geomagnetically disturbed periods the precipitational loss of energetic electrons from the outer radiation belt of the earth can readily provide the major ionization source for the mesosphere and upper stratosphere. One particularly intense manifestation of this interaction between the radiation belts and the lower atmosphere is the relativistic electron precipitation (REP) event which occurs at subauroral latitudes during magnetospheric substorm activity. At relativistic energies the precipitating electrons produce copious fluxes of energetic bremsstrahlung x-rays, the major portion of which penetrate deep into the stratosphere before undergoing excitation and ionization collisions with the neutral atmosphere. If such REP events occur more than a few percent of the time, they can, on an annual basis, provide a local source of upper stratospheric nitric oxide molecules (via the dissociation of molecular nitrogen) comparable to that from either galactic cosmic rays or energetic solar proton events. Since nitric oxide plays a major role in the removal of stratospheric ozone, it appears that the influence of REP events must also be considered in future photochemical modeling of the terrestrial ozone layer. 相似文献
10.
Records of now-extinct short-lived nuclides in meteorites provide information about the formation and evolution of the solar system. We have found excess 10B that we attribute to the decay of short-lived 10Be (half-life 1.5 million years) in hibonite grains from the Murchison meteorite. The grains show no evidence of decay of two other short-lived nuclides-26Al (half-life 700,000 years) and 41Ca (half-life 100,000 years)-that may be present in early solar system solids. One plausible source of the observed 10Be is energetic particle irradiation of material in the solar nebula. An effective irradiation dose of approximately 2 x 10(18) protons per square centimeter with a kinetic energy of >/=10 megaelectronvolts per atomic mass unit can explain our measurements. The presence of 10Be, coupled with the absence of 41Ca and 26Al, may rule out energetic particle irradiation as the primary source of 41Ca and 26Al present in some early solar system solids and strengthens the case of a stellar source for 41Ca and 26Al. 相似文献
11.
Power is supplied to a planet's magnetosphere from the kinetic energy of planetary spin and the energy flux of the impinging solar wind. A fraction of this power is available to drive numerous observable phenomena, such as polar auroras and planetary radio emissions. In this report our present understanding of these power transfer mechanisms is applied to Uranus to make specific predictions of the detectability of radio and auroral emissions by the planetary radio astronomy (PRA) and ultraviolet spectrometer (UVS) instruments aboard the Voyager spacecraft before its encounter with Uranus at the end of January 1986. The power available for these two phenomena is (among other factors) a function of the magnetic moment of Uranus. The date of earliest detectability also depends on whether the predominant power source for the magnetosphere is planetary spin or solar wind. The magnetic moment of Uranus is derived for each power source as a function of the date of first detection of radio emissions by the PRA instrument or auroral emissions by the UVS instrument. If we accept the interpretation of ultraviolet observations now available from the Earth-orbiting International Ultraviolet Explorer satellite, Uranus has a surface magnetic field of at least 0.6 gauss, and more probably several gauss, making it the largest or second-largest planetary magnetic field in the solar system. 相似文献
12.
Sandel BR Shemansky DE Broadfoot AL Holberg JB Smith GR McConnell JC Strobel DF Atreya SK Donahue TM Moos HW Hunten DM Pomphrey RB Linick S 《Science (New York, N.Y.)》1982,215(4532):548-553
Combined analysis of helium (584 angstroms) airglow and the atmospheric occultations of the star delta Scorpii imply a vertical mixing parameter in Saturn's upper atmosphere of K (eddy diffusion coefficient) approximately 8 x 10(7) square centimeters per second, an order of magnitude more vigorous than mixing in Jupiter's upper atmosphere. Atmospheric H(2) band absorption of starlight yields a preliminary temperature of 400 K in the exosphere and a temperature near the homopause of approximately 200 K. The energy source for the mid-latitude H(2) band emission still remains a puzzle. Certain auroral emissions can be fully explained in terms of electron impact on H(2), and auroral morphology suggests a link between the aurora and the Saturn kilometric radiation. Absolute optical depths have been determined for the entire C ring andparts of the A and B rings. A new eccentric ringlet has been detected in the C ring. The extreme ultraviolet reflectance of the rings is fairly uniform at 3.5 to 5 percent. Collisions may control the distribution of H in Titan's H torus, which has a total vertical extent of approximately 14 Saturn radii normal to the orbit plane. 相似文献
13.
Vogt RE Cook WR Cummings AC Garrard TL Gehrels N Stone EC Trainor JH Schardt AW Conlon T Lal N McDonald FB 《Science (New York, N.Y.)》1979,204(4396):1003-1007
The observations of the cosmic-ray subsystem have added significantly to our knowledge of Jupiter's magnetosphere. The most surprising result is the existence of energetic sulfur, sodium, and oxygen nuclei with energies above 7 megaelectron volts per nucleon which were found inside of Io's orbit. Also, significant fluxes of similarly energetic ions reflecting solar cosmic-ray composition were observed throughout the magnetosphere beyond 11 times the radius of Jupiter. It was also found that energetic protons are enhanced by 30 to 70 percent in the active hemisphere. Finally, the first observations were made of the magnetospheric tail in the dawn direction out to 160 Jupiter radii. 相似文献
14.
为了找出内蒙古兴安盟乌兰浩特农业种植区的酸雨时空变化与分布特征,并采取有效的防治措施以减少酸雨的影响。本研究利用内蒙古兴安盟乌兰浩特市农业种植区2006—2015年446个降水样本的pH值、电导率、酸雨频率等,运用统计分析,结果得出：年降水平均pH值呈波动递减趋势,平均电导率呈下降趋势,酸雨频率为1.9%~3.6%,酸雨级别为较弱酸雨并属酸雨偶发区。按降水量级划分,暴雨pH值最小,小雨pH值最大;小雨电导率最大,暴雨电导率最小。按四季划分,夏季pH值最小,春季pH值最大;夏季电导率最小,春季电导率最大。按风向划分,ESE风向的pH值最小,SSE风向的pH值最大;E风向电导率最大,SW风向电导率最小。由于pH值呈波动递减趋势,建议相关部门开发新能源,如太阳能、水能、风能等;工业生产排放的气体处理达标后再排放,在城市周边地区种植对二氧化硫有吸收能力的植物,如云杉、侧柏等。 相似文献
15.
Broadfoot AL Herbert F Holberg JB Hunten DM Kumar S Sandel BR Shemansky DE Smith GR Yelle RV Strobel DF Moos HW Donahue TM Atreya SK Bertaux JL Blamont JE McConnell JC Dessler AJ Linick S Springer R 《Science (New York, N.Y.)》1986,233(4759):74-79
Data from solar and stellar occultations of Uranus indicate a temperature of about 750 kelvins in the upper levels of the atmosphere (composed mostly of atomic and molecular hydrogen) and define the distributions of methane and acetylene in the lower levels. The ultraviolet spectrum of the sunlit hemisphere is dominated by emissions from atomic and molecular hydrogen, which are kmown as electroglow emissions. The energy source for these emissions is unknown, but the spectrum implies excitation by low-energy electrons (modeled with a 3-electron-volt Maxwellian energy distribution). The major energy sink for the electrons is dissociation of molecular hydrogen, producing hydrogen atoms at a rate of 10(29) per second. Approximately half the atoms have energies higher than the escape energy. The high temperature of the atmosphere, the small size of Uranus, and the number density of hydrogen atoms in the thermosphere imply an extensive thermal hydrogen corona that reduces the orbital lifetime of ring particles and biases the size distribution toward larger particles. This corona is augmented by the nonthermal hydrogen atoms associated with the electroglow. An aurora near the magnetic pole in the dark hemisphere arises from excitation of molecular hydrogen at the level where its vertical column abundance is about 10(20) per square centimeter with input power comparable to that of the sunlit electroglow (approximately 2x10(11) watts). An initial estimate of the acetylene volume mixing ratio, as judged from measurements of the far ultraviolet albedo, is about 2 x 10(-7) at a vertical column abundance of molecular hydrogen of 10(23) per square centimeter (pressure, approximately 0.3 millibar). Carbon emissions from the Uranian atmosphere were also detected. 相似文献
16.
Modern global climate change 总被引：5，自引：0，他引：5
Modern climate change is dominated by human influences, which are now large enough to exceed the bounds of natural variability. The main source of global climate change is human-induced changes in atmospheric composition. These perturbations primarily result from emissions associated with energy use, but on local and regional scales, urbanization and land use changes are also important. Although there has been progress in monitoring and understanding climate change, there remain many scientific, technical, and institutional impediments to precisely planning for, adapting to, and mitigating the effects of climate change. There is still considerable uncertainty about the rates of change that can be expected, but it is clear that these changes will be increasingly manifested in important and tangible ways, such as changes in extremes of temperature and precipitation, decreases in seasonal and perennial snow and ice extent, and sea level rise. Anthropogenic climate change is now likely to continue for many centuries. We are venturing into the unknown with climate, and its associated impacts could be quite disruptive. 相似文献
17.
我国土地利用与碳排放的关系研究 总被引：1，自引：0，他引：1
采用碳排放系数法对全国林地、草地、农作物用地及建设用地的碳排放量进行了计算,并分析了2003～2009年碳排放总量、碳源、碳汇、建设用地碳排放、碳源碳汇比、人均碳排放量、每平方公里碳排放量等7项碳排放指标的变化趋势及区域性差异。结果表明,7年间碳排放量不断增加,但增加速度有所减缓;碳排放量较大的地区集中在环渤海地区、长江三角洲和珠江三角洲的周围省份。并提出建立生态碳汇补偿机制、将碳排放量纳入政绩考核体系、优化土地管理,促进减少碳排放量的相关对策与建议。 相似文献
18.
Porco CC West RA McEwen A Del Genio AD Ingersoll AP Thomas P Squyres S Dones L Murray CD Johnson TV Burns JA Brahic A Neukum G Veverka J Barbara JM Denk T Evans M Ferrier JJ Geissler P Helfenstein P Roatsch T Throop H Tiscareno M Vasavada AR 《Science (New York, N.Y.)》2003,299(5612):1541-1547
The Cassini Imaging Science Subsystem acquired about 26,000 images of the Jupiter system as the spacecraft encountered the giant planet en route to Saturn. We report findings on Jupiter's zonal winds, convective storms, low-latitude upper troposphere, polar stratosphere, and northern aurora. We also describe previously unseen emissions arising from Io and Europa in eclipse, a giant volcanic plume over Io's north pole, disk-resolved images of the satellite Himalia, circumstantial evidence for a causal relation between the satellites Metis and Adrastea and the main jovian ring, and information on the nature of the ring particles. 相似文献
19.
利用Daniel的趋势检验、因子相关分析等方法,分析1986～2010年长沙市主要空气污染物浓度、中国SO2排放量的年际变化特征,以及两者与长沙年降水酸性的相关性,同时讨论了致酸物质的传播路径,还对可能有影响的气象要素进行相关性分析,以期探索酸雨预报提供预报因子。结果表明,长沙市年降水酸性呈现一次明显的"脉动"变化,酸雨性质已转为硫酸、硝酸混合型;降水酸度并没有随当地SO2的浓度下降而下降,尚不能说明当地近地层致酸污染物的排放是形成该地酸雨的主要原因;中国大范围SO2的排放量与年降水酸性关系密切;影响长沙年降水酸性的主要致酸物质来自全球的排放,其中西南地区、华南地区的排放起重要作用;所选气象因子的相关性不理想,但霾日与年降水酸性呈分段性显著正相关,浮尘污染增加降水酸性。 相似文献
20.
McComas DJ Allegrini F Bagenal F Crary F Ebert RW Elliott H Stern A Valek P 《Science (New York, N.Y.)》2007,318(5848):217-220
Jupiter's magnetotail is the largest cohesive structure in the solar system and marks the loss of vast numbers of heavy ions from the Jupiter system. The New Horizons spacecraft traversed the magnetotail to distances exceeding 2500 jovian radii (R(J)) and revealed a remarkable diversity of plasma populations and structures throughout its length. Ions evolve from a hot plasma disk distribution at approximately 100 R(J) to slower, persistent flows down the tail that become increasingly variable in flux and mean energy. The plasma is highly structured-exhibiting sharp breaks, smooth variations, and apparent plasmoids-and contains ions from both Io and Jupiter's ionosphere with intense bursts of H(+) and H(+)(3). Quasi-periodic changes were seen in flux at approximately 450 and approximately 1500 R(J) with a 10-hour period. Other variations in flow speed at approximately 600 to 1000 R(J) with a 3- to 4-day period may be attributable to plasmoids moving down the tail. 相似文献