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Trafton, L.

Publications and source records attributed to Trafton, L..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

The atmospheres of the outer planets and satellites

Recent research results concerning the atmospheres of the outer planets and satellites are presented, covering Pluto, Triton, Neptune, Uranus, Titan, Saturn, and Io. In addition to presenting analyses of physical properties and atmospheric chemical composition, attention is given to (1) the origin of Pluto; (2) the possible variability of Triton; (3) the rotation periods of Uranus and Neptune, as well as their effective temperatures and internal heating, haze distribution, thermal structure, and weather and seasonal changes; (4) the seasonal and long-term changes of Titan, in addition to its thermal structure; (5) the dust and haze distribution of Saturn; and (6) Io's gaseous plasma and neutral torio. The data include Voyager 1 and 2 results for Io, along with Pioneer 11 results for Saturn and Titan.

Trafton, L.↗
NASA NTRS1981

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 accommodated 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.

Trafton, L.↗
NASA NTRS1980

An explanation for the alternating north-south asymmetry of Io's sodium cloud

The hot Jovian plasma torus discovered by Voyager 1 is responsible for the periodic intensity variations of Io's sodium cloud, which are correlated with Io's magnetic latitude. The plasma torus must be a long-lived phenomenon in spite of its apparent absence at the time of the Pioneer flybys. The hot electrons (100,000 K) must be concentrated about one Jupiter radius from the magnetic equator in order to produce the observed variations. Electron impact ionization in the hot plasma torus is strong enough to form and to maintain Io's ionosphere; the hot plasma torus may be the dominant agent forming the ionosphere. Io's bound atmosphere is dense enough that the plasma torus electrons cannot cause a noticeable variation in its Na emission intensity.

Trafton, L.↗
NASA NTRS1980

The Jovian SII torus - Its longitudinal asymmetry

The variations with Jovian magnetic longitude observed in the intensity of the S II emission from the plasma torus surrounding Jupiter near the orbit of Io are investigated. Spectrographic observations of S II emission from 2.1 to 8.3 Jupiter radii from the planet obtained from 1976 to 1979 were examined to determine emission intensities in relation to position. The detected emission is found to be sharply confined to a magnetic latitude within 12 deg of the equator and a region inside 6.7 Jupiter radii, just outside of Io's orbit, with maximum emission at a magnetic longitude of 60 deg. The region of maximum brightness is observed to include the active centers for the currents expected in the flux tubes connected with Io, support of the magnetic anomaly models of Dressler and Hill (1979). Electron temperatures between 10 to the 3.92 and 10 to the 4.80, and densities of 10 to the 4.2/cu cm and a S II column abundance of 1.5 x 10 to the 13th/sq cm are estimated for the brightness region near the ansa of the emission torus. An order of magnitude difference between S II column abundances obtained in the present investigation and found by Brown (1978) is attributed to a change in sulfur content, possibly related to Ionian volcanic activity, while electron temperatures and densities are found to remain fairly constant.

Trafton, L.↗
NASA NTRS1980

The D/H ratio in the atmosphere of Uranus - Detection of the R sub 5 /1/ line of HD

Observations of Uranus during the 1975, 1976, and 1978 apparitions reveal a weak absorption at the wavelength of the R5(1) line of HD with equivalent width 1.0 + or - 0.4 mA. The D/H ratio in Uranus' atmosphere implied by this line and other published spectra is (0.000048 + or - 0.000015), and may not be significantly different from that in the atmospheres of Jupiter and Saturn. In addition, the spectra exhibit two weak absorptions at 6044.76 + or - 0.02 and 6045.54 + or 0.02 A which were not identifiable. No trace of absorption is visible near these wavelengths or near the HD wavelength in a laboratory spectrum of 4.92 km-am CH4 which was obtained in an attempt to identify these absorption features and to verify that the HD feature does not arise from CH4.

Trafton, L.↗
NASA NTRS1980

The distribution of sodium in Io's cloud - Implications

Models for the distribution of sodium in Io's vicinity and in a disk in Io's orbital plane, compared with observational data, support the arguments that (1) Io is the source of the sodium; (2) sodium is ejected from the inside hemisphere and most of the high velocity sodium which is observed is ejected from the leading inside quadrant; (3) most of the sodium leads Io in Io's vicinity but follows Io at distances of more than Jupiter radii from Jupiter; (4) a significant fraction of the sodium flux is ejected at large angles with respect to Io's orbital plane; (5) the source velocity distribution has a pronounced high-velocity tail; and (6) impact ionization by electrons is significant at large distances from Io.

Macy, W.↗
NASA NTRS1979

On seasonal phenomena in Saturn's atmosphere - New observations of Saturn's 3nu3 methane band

Saturn's 3nu3 CH4 band has been reobserved during April-June 1976, using the same telescope and spectrographic set-up used to study this band during the 1970 apparition. Direct comparison of the ratio spectra Saturn/moon reveals greater absorption in the manifold cores during 1976, but the increase is not as pronounced as that for the stronger CH4 bands. The rotational temperature and effective pressure of this band did not change significantly. These results are interpreted in terms of a possibly seasonal settling of the upper boundary of Saturn's atmospheric haze layer.

Trafton, L.↗
NASA NTRS1978

Saturn's atmosphere: Results of recent investigations

Saturn apparently has a high clear layer of H2 under which lies a comparable layer rich in dusty material. Beneath this is a thicker layer consisting mostly of H2 mixed with haze particles. An NH3 cloud deck probably lies below this layer. Evidence for seasonal variations is presented in the form of changes in the NH3, CH4 and H2 absorptions. Finally, the latest mixing ratios for the gaseous constituents are summarized.

Trafton, L.↗
NASA NTRS1978

Titan's atmosphere: Comments on haze content, methane abundance, band shapes, and hydrogen upper limit

The existence of scatterers in Titan's atmosphere was demonstrated in a paper published in the Astrophysical Journal three years ago. This conclusion was not affected by recent laboratory investigations showing that certain CH4 bands are independent of pressure because it was shown that the reflecting layer model failed to explain Titan's CH4 absorptions regardless on which portion of the curve of growth Titan's CH4 lines lie. Saturn's atmosphere was utilized along the central meridian for studies of CH4 absorption, and to show that the conclusion is insensitive to the moderate scattering there. The quite pronounced role of scattering in Titan's atmosphere strongly suggests that Titan's surface is obscured.

Trafton, L.↗
NASA NTRS1978

On the deuterium-to-hydrogen ratio in the atmosphere of Uranus

Photoelectric observations and recently published laboratory measurements of HD imply an upper limit on the deuterium-to-hydrogen ratio in Uranus's atmosphere of D/H less than 9.6 x 10 to the -5th power. This is much closer to values currently being proposed for Jupiter

Trafton, L.↗
NASA NTRS1978

On the distribution of sodium in the vicinity of Io

The contribution of scattering in a telescope to measurements of the size of Io's sodium cloud and to the distribution of emission intensity in the cloud is investigated. The brightest regions, within 30 arcsec of Io near opposition and along the equatorial plane, are relatively undistorted, but regions further than 45 arcsec away and not close to the equatorial plane are very likely to consist mainly of scattered light. Portions of the cloud in the vicinity of the magnetic equator are also mostly scattered light when Io is near extreme magnetic latitude. The equatorial torus, however, extends up to 20 arcmin from Jupiter. The large size of the cloud is thus confirmed. High-resolution line profile shapes indicate that sodium streams from Io preferentially in the forward direction with velocities distributed up to 18 km/sec. The observed wavelength shifts of the peak intensities from Io's rest frame are compatible with a cloud streaming through a bound atmospheric component, but they could also be caused by a velocity distribution peaked at very low velocities.

Trafton, L.↗
NASA NTRS1977

Uranus' rotational period

A modified spectroscopic technique was applied to determine the rotational period of Uranus and the orientation of the projected spin axis of the planet. The method consists in obtaining a series of spectra for both a nonrotated planet disk and for a disk rotated 180 degrees. Ignoring the effects of seeing in analyzing the spectra for no rotation of the disk leads to a lower limit on the period, and for a disk rotated 180 degrees, ignoring the seeing in the modeling of the spectra leads to an upper limit on the period. When blurring from seeing and guiding errors are added to the modeling for both image orientations and the model spectra are compared to the observations, both the period and the degree of blurring are obtained simultaneously. The results gave a period of rotation of Uranus 23 + 5 or - 2 hr.

Trafton, L.↗
NASA NTRS1977

The abundances of ammonia in the atmospheres of Jupiter, Saturn, and Titan

An investigation of low-resolution ratio spectra of Jupiter, Saturn, and Titan in the region 5400-6500 A has permitted new evaluations of ammonia absorption bands. The distribution of ammonia over the disk of Jupiter is very inhomogeneous. The carbon-to-nitrogen ratio is distinctly different from the solar value, but this is probably a result of uneven mixing of methane and ammonia, as suggested previously by Kuiper (1952), rather than a compositional anomaly. The abundancy of ammonia on Saturn also shows spatial variations, but appears constant in time over a 3-yr period. Two weak, unidentified absorptions were discovered in the red region of Titan's spectrum, in the absence of any detectable ammonia.

Woodman, J. H.↗
NASA NTRS1977

Venus - On the phase variation of CO2 line profiles

The shapes of Venus' CO2 profiles are found to vary with solar phase angle. High-resolution spectra of the P16 and P14 lines in the 8689- and 7820-A bands, respectively, are presented for phase angles ranging from 6 to 158 deg. The scattering mean free path at 80 mbar, approximately the effective pressure, is 1.7 km. Use of the van de Hulst (1974) similarity relations with simple parametric scattering models is inadequate to separate effects due to the scattering phase function from those due to inhomogeneities in depth when one attempts to determine the atmospheric structure by fitting a family of such models over a wide range of phase angles.

Macy, W., Jr.↗
NASA NTRS1977

Periodic variations in Io's sodium and potassium clouds

Spectra of Io's sodium cloud taken 7.5 to 45 sec north and south of Io at a variety of magnetic latitudes of Io obtained during 17 nights of the 1975 apparition of Jupiter confirm the weakening of the cloud in the neighborhood of Jupiter's magnetic equator. The time scale for these changes is 1.5 hours or less. For impact ionization to cause these changes, a minimum flux of 100 billion/sq cm/sec 15 eV electrons or 40 billion/sq cm/sec 8 keV protons is required. Sodium velocities near 10 km/sec are required to explain the replenishment of ionized regions of the cloud. We also obtained spectra of Io's potassium cloud on eight nights during the 1975 apparition. This cloud appears to behave like the sodium cloud as Io's magnetic latitude varies. The potassium, however, may become much weaker as Io passes through the magnetic equator. The brightest intensity measured for the 7665 A resonance line was about 1 kR at a point 7.5 sec east of Io.

Trafton, L.↗
NASA NTRS1977

Io's sodium emission profiles - Variations due to Io's phase and magnetic latitude

We present recent measurements of high-resolution sodium D2 emission line profiles of Io's atmosphere and cloud. The high-velocity skirts of these profiles are strongest when Io is on the magnetic equator where protons and heavy ions, which sputter atoms from Io's surface, are concentrated. The skirts are most prominent on the long-wavelength side of the line when Io is west of Jupiter, and they are most prominent on the short-wavelength side of the line when Io is east of Jupiter. Our observations also indicate that there is a shift in the emission peak with respect to Io which is correlated with Io's orbital phase angle.

Trafton, L.↗
NASA NTRS1977

Saturn - Long-term variation of H2 and CH4 absorptions

Results are presented for observations of various H2 quadrupole lines and CH4 absorption bands in spectra of Saturn obtained with a coude scanner at each apparition since 1969. The data are found to indicate a long-term variation in Saturn's H2 equivalent widths, a seasonal dependence of H2 line strength, and a fairly steady increase in CH4 absorption during the period from 1973 to 1976. A possible correlation between planetary shading and the strength of H2 absorption features is discussed along with seasonal variations in Saturn's NH3 cloud deck and atmospheric models that correspond to the observed H2 equivalent widths. It is suggested that: (1) significant shadowing by the rings may cause dynamical atmospheric activity due to the occurrence of a temperature gradient in the penumbral boundaries of the ring shadow in the planet's upper atmosphere; (2) cooling in the shadow may be a source of a high-altitude CH4 mist; and (3) spreading of this mist over the globe by advective winds would reduce the H2 and CH4 absorptions, as observed.

Trafton, L.↗