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Results are given of a study of the intensities, energy spectra, and angular distribution of energetic particles in the magnetosphere of Jupiter; the heliocentric radial gradient of the intensity of galactic cosmic rays; and the occurrence, intensity, and angular distribution of solar flare particles and their propagation through the interplanetary medium at large heliocentric distances.
A statistical study of the initial phases of a large number of solar particle events provides an approach for an investigation of the variability in the production process and coronal diffusion. A description is given of the procedures which are suitable for identifying the parent flare of an event, taking into account the heliocentric distribution of the flare-associated events. The determination of the proton energy spectrum at the sun is discussed along with the variation of the spectral index with the associated flare heliocentric longitude, questions concerning the source spectra and the acceleration process, and the size distribution of flare associated particle events.
The heliocentric radial distribution of the flux of hyperbolic cosmic dust particles, as measured by the Pioneer 8 and 9 spacecraft, is closely related to the radial variation of the spatial density of source or parent meteoroids. Within the limits of the experimental and theoretical uncertainties the spatial density of parent meteoroids, as deduced from the hyperbolic cosmic dust data, is found to be increasing with increasing heliocentric distance in the neighborhood of one AU. Other recent experimental evidence confirms this result. The new results also suggest that the ratio of the areal density of submicron-sized craters to the areal density of millimeter-sized craters will be less on the north-south faces of lunar rocks than on the east-west faces of the same rocks. The change in ratio is not as large as previously thought. It is noted that the solar system is not presently contributing significant amounts of dust to the interstellar medium though it may once have done so.
Direction-finding measurements with the plasma wave experiments on the HAWKEYE 1 and IMP 8 satellites are used to find the source locations of type 3 solar radio bursts in heliocentric latitude and longitude in a frequency range from 31.1 kHz to 500 kHz. Using an empirical model for the emission frequency as a function of radial distance from the sun the three-dimensional trajectory of the type 3 radio source can be determined from direction-finding measurements at different frequencies. Since the electrons which produce these radio emissions follow the magnetic field lines from the sun these measurements provide information on the three-dimensional structure of the magnetic field in the solar wind. The source locations projected into the ecliptic plane follow an Archimedian spiral. Perpendicular to the ecliptic plane the source locations usually follow a constant heliocentric latitude. With direction-finding measurements of this type it is also possible to determine the source size from the modulation factor of the received signals.
Spectrum scans have been obtained of Comet Kohoutek with a Fourier spectrometer at heliocentric distances from 0.55 to 1.05 AU. The useful spectral range is roughly 3800-8400 A and the resolution is about 10-15 A at 5000 A. Large variations occurred in the gas-to-dust ratio (pre- versus postperihelion) and in the relative strength of the NH2 bands (with heliocentric distance). There is a smaller change in the ratio of CN to C2 emission. The Swan bands of C2 show the customary anomaly in strengths implying highly non-Boltzmann distributions among vibrational levels. The red and violet CN system fluxes are in slightly better agreement with laboratory data on oscillator strengths than results on previous comets. Other species measured include Na, (O I), CH, and C3.
Direct observations of the solar wind between 1965 and 1972 indicate the existence of significant large scale (L is greater than 10 to the 6th km) turbulence in the solar system at heliocentric distances from 1 to 3 AU. These results are based on power spectra of the solar wind proton data obtained by plasma spectrometers on Pioneer 6 and Pioneer 10. The power spectra indicate that there is a power-law frequency dependence between 10 to the -4 Hz and 10 to the -3 Hz of the power spectra of the solar wind proton number density and streaming speed between 1 and 3 AU. The slopes and the amplitudes of the power spectra provide qualitative information concerning the cosmic ray diffusion tensor between 1965 and 1972 and at heliocentric distances between 1 AU and 3 AU.
A survey has been made to identify presently operating as well as planned spacecraft which may contribute measurements of the magnetosphere or interplanetary medium during the IMS. The total set consists of 25 scientific earth-orbiting, 9 heliocentric, and 17 communication, navigation or meteorological spacecraft, which carry environmental monitoring experiments. The orbital elements of each are displayed. In addition, techniques for the display of positions in various orbits are presented to illustrate how interesting configurations can be determined during the IMS. The positions of presently orbiting heliocentric spacecraft are shown at various intervals with respect to the nominal interplanetary magnetic field spiral and the earth. Plots of the latest ISEE-A orbit in solar magnetospheric co-ordinates are presented to determine neutral-sheet crossing.
Intensities of Fe XIV and Fe XIII EUV emission lines obtained at coronal locations beyond the limb by the Goddard spectroheliograph on the OSO 7 satellite have been corrected for the wavelength dependence of the instrument's sensitivity and have been Abel-inverted to provide a valid comparison with theoretical predictions for each ion. Details of the Abel-inversion procedure are given, including explicit formulas for application of Bracewell's (1956) method. The intensity ratios of pairs of lines originating from a common level are compared with expected theoretical transition probability ratios over a range of heliocentric distance; deviations in some cases yield information about adjacent unclassified lines. Comparison of the observations with predictions for Fe XIV and Fe XIII shows generally good agreement, with a few interesting discrepancies that may imply a corresponding need for more accurate collisional excitation cross sections. The same comparison yields the variation of electron density with heliocentric radius for each ion separately; the two density functions are found to agree within a factor of three.
The three-dimensional geometries of two classes of interplanetary shock waves are analyzed: (1) the more or less spherical shock wave originating from some short-lived solar event, such as a solar flare, and (2) the corotating shock pair formed by the interaction of long-lived solar wind streams. The systematic distortion of a spherical wave due to persistent latitudinal solar wind structure should amount to 25 deg for an equator-to-pole solar wind speed differential of 200 km/sec. A geometrical argument is given for determining the heliocentric distance of the onset of corotating shocks formed by contiguous long-lived solar streams. Estimates are obtained for the heliocentric distance to the inner edges of shock waves as a function of speed difference between the streams and as a function of heliographic latitude. Means by which the three-dimensional structures studied can be observed by out-of-the-ecliptic space missions are discussed.
Potential future manned space flight missions for the time after the development of the space transportation system with the space shuttle are considered, taking into account a sequence of activities concerning a gradually increasing penetration of space by man. The activities are related to the permanent occupancy of near-earth space, the permanent occupancy of near-moon space, the full self-sufficiency of man in earth-moon space, and the permanent occupancy of heliocentric space. Attention is given to Mars orbiting stations, the exploration of the asteroids, comet exploration, planet engineering programs, heliocentric orbit installation, the evolution of the earth orbit space community, space industrialization technology, lunar base development, and evolutionary paths to far-future space endeavors.
The plasma instrument on Mariner 10 carried out measurements of electron density and temperature in the interplanetary medium between heliocentric distances of 0.85 and 0.45 AU. Due to the stable coronal configuration and low solar activity during the period of observation, the radial variations of these quantities could be obtained. The power-law exponent of the core temperature was measured to be -0.3 + or - 0.04, and the halo temperature was found to be almost independent of heliocentric distance. The exponent of the power law for the density variation was 2.5 + or - 0.2 and the extrapolated value at 1 AU was consistent with measured values during the same period. Calculations of the core electron self-collision time, and the core-halo equipartition time were made as a function of radial distance. These measurements indicate a macroscale picture of a Coulomb-collisional core and a collisionless isothermal halo. Extrapolating back to the sun, core and halo temperatures become equal at a radial distance of approx. 2-15 radii.
A class of comets, of which Comet Kohoutek (1973f) is typical, show total as well as monochromatic brightness asymmetries about perihelion. They are fainter after perihelion than before at the same heliocentric distance. A model of the cometary nucleus consisting of a growing nonvolatile dust mantle surrounding a volatile icy core is used to discuss this phenomenon. Numerical results are obtained for Comet Kohoutek (1973f). It is found that dust mantles of thickness in the range of 10-75 cm can be grown by perihelion passage for various values of the thermal conductivity of the dust if there is no substantial dust blow-off by the sublimating volatiles. The thermal conductivity of the dust mantle is quite small and is dominated by 'radiative conductivity' for heliocentric distances less than about 2 AU. Since the radiative conductivity is larger for larger grain size, the thickest mantle corresponds to coarsest matrix. The production rate of the 'parent-molecules' as well as the monochromatic brightness of their 'daughter' products increases less steeply than in the mantleless case, as the comet approaches perihelion.
The nonsteady development of the multispecies atmosphere of a long-period comet approaching the sun is modeled, and the associated monochromatic brightness variations are discussed in terms of the varying abundances of the atmospheric species. A simple homogeneous clathrate structure, 85% of which is H2O, provides the representation for the cometary nucleus. Monochromatic brightness variations of the emission bands due to OH, CN and C2 are found to follow the law proposed by Levin (1943) for small heliocentric distance where a quasi-steady approximation is valid. However, the large time-scales of residence for emitting species leads to a breakdown of Levin's law at large heliocentric distances.
The plasma electron detector on Mariner 10 is used to obtain measurements of electron density and temperature in the interplanetary medium between heliocentric distances of 0.85 and 0.45 AU. The observations show quantitatively that the core of the electron distribution function can be described as collisional at least for radial distances within 1 AU, since with a very few well-marked exceptions associated with high-speed streams, the Coulomb collisional momentum relaxation length is less than the density scale height at all times and all radial distances at which data were obtained. It is found that the Coulomb energy exchange collisions between the core and the (test) halo population are negligible. The power law exponent of the core temperature is about -0.3, whereas the halo temperature is almost independent of heliocentric distance.
Interference filter photometry was taken of Comet Encke on June 14, 1974 (1.07 AU heliocentric distance, postperihelion) at the CTIO (Cerro Tololo Interamerican Observatory) 150-cm reflector. Production rates were calculated as 4.1 x 10 to the 23nd power mol/sec for CN, 5.3 x 10 to 23nd power mol/sec for C3, and 4.3 x 10 to the 24th power mol/sec for C2. These are about three times smaller than at comparable heliocentric distance preperihelion, assuming a value of 100 for the ratio H2O/(C2 + C3 + CN). An upper limit was placed on the production of nonvolatiles at about one-third that of volatiles in mass by assuming a bulk density of 1 g/cu cm, a particle geometric albedo of 0.1, and a phase function of 0.2.
Simultaneous solar-wind proton data obtained at several heliocentric distances during radial alignments are compared. The radial variations associated with two high-speed streams in the solar wind are studied as examples of the radial evolution of the solar-wind speed distribution and of high-speed streams in the solar wind as observed in the ecliptic plane in 1973. Pioneer 11 data on high-speed streams in the solar wind observed at about 1.5 and 3.7 AU are compared with the corresponding high-speed-stream data obtained at earth. These analyses indicate that as these high-speed streams propagated to these extended heliocentric distances, there was an erosion of the highest speeds and a general narrowing of the speed distribution. These observations are consistent with the exchange of momentum in the solar wind between high-speed streams and low-speed streams as they propagate outward from the sun.
With the advent of mission planning for spacecraft encounters with comets in the 1980s, the lack of basic data on cometary nuclei has become quite apparent and a real problem. More effort is needed on all comets, with special attention given to probable space flight targets such as Tempel 2. The paper presents medium-spectral-resolution spectrophotometry of P/Tempel 2, made at heliocentric distances of 2.66 and 3.02 AU on two dates in 1978. It is shown that optical spectrophotometry of comet Tempel 2 near 3 AU heliocentric distance places strict limits on its activity, the modeled CN production rate having an upper limit of 6 times 10 to the 21st molecules per sec. The observations of P/Tempel 2 are compatible with a bare nucleus of 1.6 km radius (geometric albedo = 0.15) and somewhat redder than the sun.
Solar wind electron density power spectra in the solar equatorial region are inferred from observations of phase scintillations and spectral broadening made with the Viking, Helios, and Pioneer spacecraft. The heliocentric distance range covered is 2-215 solar radii and for some observations close to the sun the spectra extend to fluctuation frequencies as high as 100 Hz. For heliocentric distances of about 20 solar radii the equivalent spacecraft-measured one-dimensional density spectrum is well modeled by a single power law in the frequency range 0.0001-0.05 Hz. The flattening of the density spectrum within 20 solar radii is presumably associated with energy deposition in the near-sun region and acceleration of the solar wind.