The hot plasma environment at jupiter: ulysses results

Measurements of the hot plasma environment during the Ulysses flyby of Jupiter have revealed several new discoveries related to this large rotating astrophysical system. The Jovian magnetosphere was found by Ulysses to be very extended, with the day-side magnetopause located at approximately 105 Jupiter radii. The heavy ion (sulfur, oxygen, and sodium) population in the day-side magnetosphere increased sharply at approximately 86 Jupiter radii. This is somewhat more extended than the "inner" magnetosphere boundary region identified by the Voyager hot plasma measurements. In the day-side magnetosphere, the ion fluxes have the anisotropy direction expected for corotation with the planet, with the magnitude of the anisotropy increasing when the spacecraft becomes more immersed in the hot plasma sheet. The relative abundances of sulfur, oxygen, and sodium to helium decreased somewhat with decreasing radial distance from the planet on the day-side, which suggests that the abundances of the Jupiter-derived species are dependent on latitude. In the dusk-side, high-latitude region, intense fluxes of counter-streaming ions and electrons were discovered from the edge of the plasma sheet to the dusk-side magnetopause. These beams of electrons and ions were found to be very tightly aligned with the magnetic field and to be superimposed on a time- and space-variable isotropic hot plasma background. The currents carried by the measured hot plasma particles are typically approximately 1.6 x 10(-4) microamperes per square meter or approximately 8 x 10(5) amperes per squared Jupiter radius throughout the high-latitude magnetosphere volume. It is likely that the intense particle beams discovered at high Jovian latitudes produce auroras in the polar caps of the planet.     

The magnetosphere of uranus: hot plasma and radiation environment

The low-energy charged-particle (LECP) instrument on Voyager 2 measured lowenergy electrons and ions near and within the magnetosphere of Uranus. Initial analysis of the LECP measurements has revealed the following. (i) The magnetospheric particle population consists principally of protons and electrons having energies to at least 4 and 1.2 megaelectron volts, respectively, with electron intensities substantially excceding proton intensities at a given energy. (ii) The intensity profile for both particle species shows evidence that the particles were swept by planetry satellites out to at least the orbit of Titania. (iii) The ion and electron spectra may be described by a Maxwellian core at low energies (less than about 200 kiloelectron volts) and a power law at high energies (greater than about 590 kiloelectron volts; exponentmicro, 3 to 10) except inside the orbit of Miranda, where power-law spectra (micro approximately 1.1 and 3.1 for electrons and protons, respectively) are observed. (iv) At ion energies between 0.6 and 1 megaelectron volt per nucleon, the composition is dominated by protons with a minor fraction (about 10(-3)) of molecular hydrogen; the lower limit for the ratio of hydrogen to helium is greater than 10(4). (v) The proton population is sufficiently intense that fluences greater than 10(16) per square centimeter can accumulate in 10(4) to 10(') years; such fluences are sufficient to polymerize carbon monoxide and methane ice surfaces. The overall morphology of Uranus' magnetosphere resembles that of Jupiter, as evidenced by the fact that the spacecraft crossed the plasma sheet through the dawn magnetosheath twice per planetary rotation period (17.3 hours). Uranus' magnetosphere differs from that of Jupiter and of Saturn in that the plasma 1 is at most 0.1 rather than 1. Therefore, little distortion ofthe field is expected from particle loading at distances less than about 15 Uranus radii.     

Plasma observations near jupiter: initial results from voyager 1

Extensive measurements of low-energy positive ions and electrons were made throughout the Jupiter encounter of Voyager 1. The bow shock and magneto-pause were crossed several times at distances consistent with variations in the upstream solar wind pressure measured on Voyager 2. During the inbound pass, the number density increased by six orders of magnitude between the innermost magnetopause crossing at approximately 47 Jupiter radii and near closest approach at approximately 5 Jupiter radii; the plasma flow during this period was predominately in the direction of corotation. Marked increases in number density were observed twice per planetary rotation, near the magnetic equator. Jupiterward of the Io plasma torus, a cold, corotating plasma was observed and the energylcharge spectra show well-resolved, heavy-ion peaks at mass-to-charge ratios A/Z* = 8, 16, 32, and 64.     

Preliminary results on the atmospheres of io and jupiter from the pioneer 10 s-band occultation experiment

The preliminary analysis of data from the Pioneer 10 S-band radio occultation experinment has revealed the presence of an ionosphere on the Jovian satellite Io (JI) having an electron density peak of about 6 x 10(4) electrons per cubic centimeter at an altitude of approximately 60 to 140 kilometers. This suggests the presence of an atmosphere having a surface number density of about 10(10) to 10(12) per cubic centimeter, corresponding to an atmospheric surface pressure of between 10(-8) and 10(-10) bar, at or below the detection threshold of the Beta Scorpii stellar occultation. A measurement of the atmosphere of Jupiter was obtained down to the level of about 80 millibars, indicating a large temperature increase at about the 20 millibar level, which cannot be explained by the absorption of solar radiation by methane alone and can possibly be due to absorption by particulate matter.     

Energetic electrons in the magnetosphere of jupiter

Observations of energetic electrons ( greater, similar 0.07 million electron volts) show that the outer magnetosphere of Jupiter consists of a thin disklike, quasitrapping region extending from about 20 to 100 planetary radii (R(J)). This magnetodisk is confined to the vicinity of the magnetic equatorial plane and appears to be an approximate figure of revolution about the magnetic axis of the planet. Hard trapping is observed within a radial distance of about 20 R(J). The omnidirectional intensity J(0) of electrons with energy greater, similar 21 million electron volts within the region 3 r 20 R(J) is given by the following provisional expression in terms of radial distance r and magnetic latitude theta: J(0) = 2.1 x 10(8) exp[-(r/a) - (theta/b)(2)]. In this expression J(0) is particles per square centimeter per second; a = 1.52 R(J) for 3 相似文献   

Pioneer 10 jovian encounter: radiation dose and implications for biological lethality

In its recent Jupiter flyby Pioneer 10 passed through a belt of intense particulate radiation. The radiation dose on the outer surface of the spacecraft was at least 4.9 x 10(5) rads from electrons plus 2.9 x 10(6) rads from protons, sufficient to cause significant microbial decontamination. The radiation dose inside Pioneer 10, approximately 2.8 x 10(5) rads, was less likely to cause microbial decontamination but would be lethal to man and to most multicellular biological organisms.     

Sea level variation as an indicator of Florida current volume transport: comparisons with direct measurements

Sea level measurements from tide gauges at Miami, Florida, and Cat Cay, Bahamas, and bottom pressure measurements from a water depth of 50 meters off Jupiter, Florida, and a water depth of 10 meters off Memory Rock, Bahamas, were correlated with 81 concurrent direct volume transport observations in the Straits of Florida. Daily-averaged sea level from either gauge on the Bahamian side of the Straits was poorly correlated with transport. Bottom pressure off Jupiter had a linear coefficient of determination ofr(2) = 0.93, and Miami sea level, when adjusted for weather effects, had r(2) = 0.74; the standard errors of estimating transports were +/- 1.2 x 10(6) and +/- 1.9 x 10(6) cubic meters per second, respectively. A linear multivariate regression, which combined bottom pressure, weather, and the submarine cable observations between Jupiter and the Bahamas, had r(2) = 0.94 with a standard error of estimating transport of +/- 1.1 x 10(6) cubic meters per second. These results suggest that a combination of easily obtained observations is sufficient to adequatelv monitor the daily volume transport fluctuations of the Florida Current.     

Gravitational parameters of the jupiter system from the Doppler tracking of pioneer 10

Preliminary analyses of Doppler data from Pioneer 10 during its encounter with Jupiter indicate that the mass of Io is about 20 percent greater than previously thought and that Io's mean density is about 3.5 grams per cubic centimeter. A determination of the dynamical flattening of Jupiter (a - b)/a (where a is the semimajor axis and b is the semiminor axis) is found to lie in the neighborhood of 0.065, which agrees with the value determined from satellite perturbations.     

Voyager 2: energetic ions and electrons in the jovian magnetosphere

The Voyager 2 encounter has enhanced our understanding of earlier results and provided measurements beyond 160 Jupiter radii (R(J)) in the magnetotail. Significant fluxes of energetic sulfur and oxygen nuclei (4 to 15 million electron volts per nucleon) of Jovian origin were observed inside 25 R(J), and the gradient in phase space density at 12 R(J) indicates that the ions are diffusing inward. A substantially longer time delay versus distance was found for proton flux maxima in the active hemisphere in the magnetotail at Jovicentric longitudes lambda(III), = 260 degrees to 320 degrees than in the inactive hemisphere at lambda(III), = 85 degrees to l10 degrees . These delays can be related to the radial motion of plasma expanding into the magnetotail, and differences in the expansion speeds between the active and inactive hemispheres can produce rarefaction regions in trapped particles. It is suggested that the 10-hour modulation of interplanetary Jovian electrons may be associated with the arrival at the dawn magnetopause of a rarefaction region each planetary rotation.     

Radio science with voyager 1 at jupiter: preliminary profiles of the atmosphere and ionosphere

A preliminarv profile of the atmosphere of Jupiter in the South Equatorial Belt shows (i) the tropopause occurring at a pressure level of 100 millibars and temperature of about 113K, (ii) a higher warm inversion layer at about the 35-millibar level, and (iii) a lower-altitude constant lapse rate matching the adiabatic value of about 2 K per kilometer, with the temperatutre reaching 150 K at the 600-millibar level. Preliminary afternoon and predawn ionospheric profiles at 12 degrees south latitude and near the equator, respectively, have topside plasma scale heights of 590 kilometers changing to 960 kilometers above an altitucde of 3500 kilometers for the dayside, and about 960 kilomneters at all measured heights above the peak for the nightside. The higher value of scale height corresponds to a plasma temperature of 1100 K under the assumption of a plasma of protons and electrons in ambipolar diffusive equilibrium. The peak electron concentration in the upper ionosphere is approximately 2 x 10(5) per cubic centimeter for the dayside and about a factor of 10 less for the nightside. These peaks occur at altitudes of 1600 and 2300 kilometers, respectively. Continuing analyses are expected to extend and refine these results, and to be used to investigate other regions and phenomena.     

High-Energy Charged Particles in the Innermost Jovian Magnetosphere

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.     

Jupiter: its captured satellites

Because of the small size and irregular orbits of the seven outer satellites of Jupiter, it is often assumed that they were derived by capture. The conditions whereby Jupiter can capture satellites have therefore been examined. Relationships derived on the basis of the three-body problem for planets in elliptical orbits enable the dimensions of the capture orbits around Jupiter to be calculated. It is found that Jupiter may capture satellites through the inner Lagrangian point when at perihelion or at aphelion. Captures at perihelion should give rise to satellites in direct orbits of 11.48 x 10(6) kilometers and capture at aphelion to retrograde orbits of 21.7 x 10(6) kilometers. The correspondence with the seven outer satellites suggests that Jupiter VI, VIl, and X in direct orbits at 11.47, 11.74, and 11.85 x 10(6) kilometers were captured at Jupiter perihelion, whereas Jupiter VIII, IX, XI, and XII in retrograde orbits of 23.5, 23.7, 22.5, and 21.2 x 10(6) kilometers were captured when Jupiter was at aphelion. Examination of the precapture orbits indicates that the seven outer satellites were derived from the asteroid belt.     

Jovian Atmosphere: Structure and Composition between the Turbopause and the Mesopause

The occultation of the star Beta Scorpii by Jupiter was observed at high time resolution in three wavelength channels. The results imply a temperature of 220 degrees K at an altitude in the Jovian atmosphere corresponding to 10(14) molecules per cubic centimeter, and temperature fluctuations of 2 degrees to 10 degrees K over vertical scales of 2 to 10 kilometers. They suggest that the vertical eddy diffusion coefficient near the turbopause has a lower limit of 7 x 10(5)K square centimeters per second, and that the turbopause lies above the altitude where the density is 5 x 10(13) molecules per cubic centimeter. Below the turbopause, the ratio of hydrogen to helium is consistent with cosmic abundances.     

Jupiter's Magnetosphere: Plasma Description from the Ulysses Flyby

Plasma observations at Jupiter show that the outer regions of the Jovian magnetosphere are remarkably similar to those of Earth. Bow-shock precursor electrons and ions were detected in the upstream solar wind, as at Earth. Plasma changes across the bow shock and properties of the magnetosheath electrons were much like those at Earth, indicating that similar processes are operating. A boundary layer populated by a varying mixture of solar wind and magnetospheric plasmas was found inside the magnetopause, again as at Earth. In the middle magnetosphere, large electron density excursions were detected with a 10-hour periodicity as planetary rotation carried the tilted plasma sheet past Ulysses. Deep in the magnetosphere, Ulysses crossed a region, tentatively described as magnetically connected to the Jovian polar cap on one end and to the interplanetary magnetic field on the other. In the inner magnetosphere and lo torus, where corotation plays a dominant role, measurements could not be made because of extreme background rates from penetrating radiation belt particles.     

Radio science with voyager at jupiter: initial voyager 2 results and a voyager 1 measure of the io torus

Voyager 2 radio signals were observed essentially continuously during a grazing occultation of the spacecraft by the southern limb of Jupiter. Intensity data show a classic atmospheric occultation profile and the effects of turbulence and ionospheric focusing and defocusing. No reliable profile of the neutral atmosphere has yet been obtained, primarily because of a combination of large trajectory uncertainties and error multiplication effects associated with the grazing geometry of the Voyager 2 occultation. Analysis of the dispersive ionospheric refraction data yields preliminary profiles for the topside ionosphere at 66.7 degrees S (entry in the evening) and 50.1 degrees S (exit in the morning) that are reversed with respect to corresponding Voyager 1 profiles in terms of plasma concentration at a fixed altitude. Plasma scale heights and temperatures of 880 kilometers, 1200 K and 1040 kilometers, 1600 K were obtained for morning and evening conditions, respectively. Preliminary reduction of the pre-encounter occultation of Voyager 1 by the Io torus yields an average plasma density of about 1000 electrons per cubic centimeter.     

Plasma wave observations near jupiter: initial results from voyager 2

This report provides an initial survey of results from the plasma wave instrument on the Voyager 2 spacecraft, which flew by Jupiter on 9 July 1979. Measurements made during the approach to the planet show that low-frequency radio emissions from Jupiter have a strong latitudinal dependence, with a sharply defined shadow zone near the equatorial plane. At the magnetopause a new type of broadband electric field turbulence was detected, and strong electrostatic emissions near the upper hybrid resonance frequency were discovered near the low-frequency cutoff of the continuum radiation. Strong whistler-mode turbulence was again detected in the inner magnetosphere, although in this case extending out to substantially larger radial distances than for Voyager 1. In the predawn tail region, continuum radiation was observed extending down to extremely low frequencies, approximately 30 hertz, an indication that the spacecraft was entering a region of very low density, approximately 1.0 x 10(-5) per cubic centimeter, possibly similar to the lobes of Earth's magnetotail.     

Protons and Electrons in Jupiter's Magnetic Field: Results from the University of Chicago Experiment on Pioneer 10

Fluxes of high energy electrons and protons are found to be highly concentrated near the magnetic equatorial plane from distances of ~ 30 to ~ 100 Jovian radii (R(J)). The 10-hour period of planetary rotation is observed as an intensity variation, which indicates that the equatorial zone of high particle fluxes is inclined with respect to the rotation axis of the planet. At radial distances [unknown] 20 R(J) the synchrotron-radiation-producing electrons with energies greater, similar 3 million electron volts rise steeply to a maximum intensity of ~ 5 x 10(8) electrons per square centimeter per second near the periapsis at 2.8 R(J). The flux of protons with energies greater, similar 30 million electron volts reaches a maximum intensity of ~ 4 x 10(6) protons per square centimeter per second at ~ 3.5 R(J) with the intensity decreasing inside this radial distance. Only for radial distances [unknown] 20 R(J) does the radiation behave in a manner which is similar to that at the earth. Burst of electrons with energies up to 30 million electron volts, each lasting about 2 days, were observed in interplanetary space beginning approximately 1 month before encounter. This radiation appears to have escaped from the Jovian bow shock or magnetosphere.     

Discovery of gaseous S2 in Io's Pele plume

Spectroscopy of Io's Pele plume against Jupiter by the Hubble Space Telescope in October 1999 revealed absorption due to S2 gas, with a column density of 1.0 +/- 0.2 x 10(16) per square centimeter, and probably also SO(2) gas with a column density of 7 +/- 3 x 10(16) per square centimeter. This SO2/S2 ratio (3 to 12) is expected from equilibration with silicate magmas near the quartz-fayalite-magnetite or wüstite-magnetite buffers. Condensed S3 and S4, probable coloring agents in Pele's red plume deposits, may form by polymerization of the S2, which is unstable to ultraviolet photolysis. Diffuse red deposits near other Io volcanoes suggest that venting and polymerization of S2 gas is a widespread feature of Io volcanism.     

Hot plasma environment at jupiter: voyager 2 results

Measurements of the hot (electron and ion energies >/=20 and >/= 28 kiloelectron volts, respectively) plasma environment at Jupiter by the low-energy charged particle (LECP) instrument on Voyager 2 have revealed several new and unusual aspects of the Jovian magnetosphere. The magnetosphere is populated from its outer edge into a distance of at least approximately 30 Jupiter radii (R(J)) by a hot (3 x 10(8) to 5 x 10(8) K) multicomponent plasma consisting primarily of hydrogen, oxygen, and sulfur ions. Outside approximately 30 R(J) the hot plasma exhibits ion densities from approximately 10(-1) to approximately 10(-6) per cubic centimeter and energy densities from approximately 10(-8) to 10(-13) erg per cubic centimeter, suggesting a high beta plasma throughout the region. The plasma is flowing in the corotation direction to the edge of the magnetosphere on the dayside, where it is confined by solar wind pressure, and to a distance of approximately 140 to 160 R(J) on the nightside at approximately 0300 local time. Beyond approximately 150 R(J) the hot plasma flow changes into a "magnetospheric wind" blowing away from Jupiter at an angle of approximately 20 degrees west of the sun-Jupiter line, characterized by a temperature of approximately 3 x 10(8) K (26 kiloelectron volts), velocities ranging from approximately 300 to > 1000 kilometers per second, and composition similar to that observed in the inner magnetosphere. The radial profiles of the ratios of oxygen to helium and sulfur to helium (相似文献