Engineering topics
Publications and source records attributed to Luthey, J. L..
The Ulysses mission ESA spacecraft with ESA and NASA experiments explores the polar regions of the sun by sending a spacecraft on a trajectory out of the ecliptic after a Jupiter flyby. After correcting for launch errors and refining the aimpoint, orbit determination results show the change and general improvement in the Jupiter arrival point. Orbit determination results are further discussed, and future plans are mentioned.
X rays in the energy band 0.2-3.0 keV have been detected coming from both polar regions of Jupiter. The observations were made in 1979 and 1981 by using the imaging proportional counter and high resolution imaging detectors on the Einstein X-ray astronomy satellite. The measured flux density of approximately 0.0006/sq cm-sec at earth corresponds to an X ray luminosity of approximately 4 x 10 to the 9th W in the 0.2- to 3.0-keV energy band. The energy spectrum of the X rays is extremely soft and can be characterized by a power law with an exponent of approximately 2.3. Detector energy resolution is insufficient to distinguish a soft line spectrum from a continuum. However, the shape of the response and the observed X ray power indicate that the source of this auroral emission is not electron bremsstrahlung as on the earth, but is most probably line emission from O and S ions with energies between 0.03 and 4.0 MeV/nucleon precipitating from the outer boundary of the Io plasma torus at L approximately 8.
Several synchrotron spectra are computed for a hypothetical Saturnian radiation belt. A monoenergetic distribution of relativistic electrons is assumed to exist in a toroidal volume in a dipole magnetic field aligned with the rotation axis. When synchrotron emission is added to the thermal component implied by observations at wavelengths shorter than 50 cm, the upturn in the total emission spectrum can become gradual to quite sharp depending on the critical wavelength and the number density of radiating electrons. As an example, the ranges of magnetic field intensity, and electron energy and density are tabulated for an estimate of the nonthermal component at the longest decimetric wavelength observation. The present observations are insufficient to determine the critical wavelength; but, for several estimates of the magnetic field loading factor, the minimum surface magnetic field intensity and minimum electron number density are computed.
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A synchrotron model with a Maxwellian energy distribution of the form e to the (-E/E sub 0) power is used in a comparison with spatially resolved radio interferometric measurements of the Jovian emission. The observations of the decimeter radiation as a function of equatorial distance at 10.4 and 21 cm wavelength were reduced to source emission/cc of source electrons in each of 16 concentric rings. The peak energies for isotropically distributed electrons exceeded the maximum energy for flat orbiting electrons, and the peaks were generally located from 2.25 to 3 Jupiter radii. Beyond 3 radii, the order of magnitude on number density became a sensitive function of pitch angle distribution. The total equatorial intensities at 75 cm wavelength were computed for (E sub 0)(r) and n(r) at different values of B sub 0. The radiative half life for electrons of initial energy E sub 0 in a dipole field was calculated and found to be nearly constant at one year or less for altitudes at and below the position in peak energy.
Synchrotron spectra were computed for a hypothetical Saturn radiation belt. A monoenergetic distribution of relativistic electrons was assumed to exist in a toroidal volume in a dipole magnetic field aligned with the rotation axis. When synchrotron emission is added to the thermal component implied by observations at wavelengths shorter than 50 cm, the upturn in the total emission spectrum may be gradual to sharp, depending on the critical wavelength and the number density of radiating electrons. With the constraint of the pressure balance equation, the ranges of magnetic field intensity, and electron energy, and density were tabulated and nomographically illustrated. For several estimates of the magnetic field loading factor, the minimum surface magnetic field intensity and minimum electron number density were computed.