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NASA NTRS1979

Mariner 9 ultraviolet spectrometer experiment - Vertical distribution of ozone on Mars

The vertical distribution of ozone in the atmosphere of Mars is computed from ultraviolet spectra obtained by the Mariner 9 spacecraft. In the Northern Hemisphere the ozone scale height is much smaller than the atmospheric scale height in midlatitudes and increases rapidly to a maximum farther north. At high latitudes (above 60 deg) there is no significant difference between the scale heights of ozone in the Northern (winter) Hemisphere and the Southern (summer) Hemisphere. Comparison of the ozone distribution with atmospheric temperature structure indicates that at some locations in the North, the density of water vapor increases with altitude, and the time for vertical mixing is about 3 days or more.

Wehrbein, W. M.↗

NASA NTRS1984

Detection of the J-10 Manifold of the Pure Rotational Band of Phosphine on Saturn

The detection of the J = 10 manifold of the pure rotational band of PH3 on Saturn is reported. The observations were made from the far-infrared cooled grating spectrometer. The wavelengths and observed brightness temperatures for the full disk plus rings are 89 + or - 3 K at 97.04 micrometer, 77 + or - 3 K at 102.72 micrometer, 77 + or - 3 K at 102.94 micrometer, and 83 + or - 3 K at 105.12 micrometers. The points of 97.04 and 105.12 micrometers establish the continuum level and the two points near 103 micrometers measure the depth of the PH3 manifold. After the flux due to the rings is subtracted, the depth of the feature is 16 + or - 6 K relative to the nearby 102 K continuum. These results are compared to theoretical models which parameterize the PH3 mixing ratio as x = x sub zero (P/P sub zero)(alpha) for P P sub zero and as x = x sub zero for P or = P, where P is the total pressure and alpha = H/h is the ratio of the dynamical scale height (H) and the scale height for decreasing the PH3 mixing ratio (h). The parameters x sub zero, P sub zero, and h were varied, as well as the H/He mixing ratio and the pressure-temperature profile. The data are well fitted using pressure-temperature profiles. The preferred values of h, P sub zero, and x sub zero imply that there is little or no PH3 above the thermal inversion and that the mixing ratio below the inversion is consistent with PH3 being 1 to 4 times overabundant relative to the solar P/H ratio.

Haas, M. R.↗

NASA NTRS1993

The influence of orography on the transport of atmospheric constituents

Given the fact that martian orography varies over a range of two scale heights (cf., about one scale height on Earth), it is thought that on Mars some aspects of the circulation should be affected to a large degree by the presence of orography. Initial results from two numerical models are presented that illustrate the effect of orography on cross-equatorial transport on Mars. On Earth, western boundary currents are found not only in the oceans as one would expect, but also in the troposphere, the most notable example being the East African Jet, which has an important effect on the monsoon circulation of the Eastern Indian Ocean. Two models were used for this investigation: a simple GCM (hereafter referred to as the SGCM); and a simple one-level barotropic model (BM). The SGCM solves the hydrostatic primitive equations on a sphere by representing model variables by spherical harmonics in the horizontal, with nonlinear terms being calculated in grid-point space. In the vertical, the model uses the sigma coordinate system in finite-difference form. The model represents the radiative processes in the atmosphere by a Newtonian relaxation to a specified zonal mean temperature state and surface drag by Rayleigh friction in the lowest model level.

Joshi, Manoj M.↗

NASA NTRS1994

Highly ionized gas in the Galactic halo

We reexamine the values of electron density n(sub e) and gas pressure P/k in the interstellar medium (ISM) of the Galactic halo, as inferred from C IV emission and absorption lines and using current C IV atomic data. In a homogeneous model with 4.7 less than or equal to log T less than or equal to 5.3, the data are consistent with 0.01 less than or equal to n(sub e) less than or equal to 0.02/cu cm and 2200 less than or equal to P/k less than or equal to 3700/cu cm K, a factor of 2-3 higher than advocated by Martin & Bowyer (1990) and comparable to the thermal pressure in the disk. If some of the C IV absorption arises from nonemitting, photoionized gas, then the inferred density and pressure will increase accordingly. The volume filling factor for homogeneous models ranges from 0.5% to 5%. Because of the constraints arising from filling factor and radiated power, most of the C IV must arise from gas near the peak of the cooling curve, at log t less than or equal to 5.6. We relate both emission-line and absorption-line observations to recent models in which turbulent mixing layers and isobarically cooling supernova remnants (SNRs) provide significant amounts of halo gas at approximately 10(exp 5.3) K and process 20-40 solar mass/yr with a power of approximately 10(exp 41) ergs/sec. Since the observed C IV and N V absorption scale heights have been reported to differ, at 4.9 kpc and 1.6 kpc, respectively, we examine inhomogeneous models with different exponential scale heights of T, P, and SN energy input. The ISM may change its character with distance above the Galactic plane, as superbubbles and mixing layers dominate over isolated SNRs as the source of the C IV. For appropiate scale heights, the midplane pressure is twice the homogeneous values quoted above. The O IV lambda 1034 diffuse emission line, which can be used as a temperature diagnostic of the hot gas, is predicted to be comparable in strength to that of C IV lambda 1549 (approximately 6000 photons/cu cm/s/sr. The ions C IV, N V, and O VI are predicted to show a decreasing trend in vertical extent, with the O IV scale height perhaps as low as approximately 1 kpc.

Shull, J. Michael↗

NASA NTRS2003

Characteristics of Mini-Magnetospheres Formed by Paleo-Magnetic Fields of Mars

The intensely and non-uniformly magnetized crustal sources generate an effective large-scale magnetic field. In the Southern hemisphere the strongest crustal fields lead to the formation of large-scale mini-magnetospheres. In the Northern hemisphere, the crustal fields are rather weak and there are only isolated mini-magnetospheres. Re-connection with the interplanetary magnetic field (IMF) occurs in many localized regions. This may occur not only in cusp-like structures above nearly vertical field anomalies but also in halos extending several hundreds of kilometers from these sources. Re-connection will permit solar wind (SW) and more energetic particles to precipitate into and heat the neutral atmosphere. Electron density profiles of the ionosphere of Mars derived from radio occultation data obtained by the Radio Science Mars Global Surveyor (MGS) experiment are concentrated in the near polar regions. The effective scale-height of the neutral atmosphere density in the vicinity of the ionization peak has been derived for each of the profiles studied. The effective scale-heights have been compared with the crustal magnetic fields measured by the MGS Magnetometer/Electron Reflectometer (MAG/ER) experiment. A significant difference between the large-scale mini-magnetospheres and regions outside of them has been found. The neutral atmosphere is cooler inside the large-scale mini-magnetospheres. It appears that outside of the cusps the strong crustal magnetic fields prevent additional heating of the neutral atmosphere by direct interaction of the SW. The scale-height of the neutral atmosphere density derived from the experiment with the MGS Accelerometer has been compared with MAG/ER data. The scale-height was found to be usually larger than mean value near the boundaries of potential mini-magnetospheres and around cusps . It may indicate that the paleo-magnetic/IMF field re-connection is characteristic of the mini-magnetospheres at Mars.

N F Ness↗

NASA NTRS1995

Probing the galactic disk and halo. 2: Hot interstellar gas toward the inner galaxy star HD 156359

We present Goddard High Resolution Spectrograph intermediate-resolution measurements of the 1233-1256 A spectral region of HD 156396, a halo star at l = 328.7 deg, b = -14.5 deg in the inner Galaxy with a line-of sight distance of 11.1 kpc and a z-distance of -2.8 kpc. The data have a resolution of 18 km/s Full Width at Half Maximum (FWHM) and a signal-to-noise ratio of approximately 50:1. We detect interstellar lines of Mg II, S II, S II, Ge II, and N V and determine log N/(Mg II) = 15.78 +0.25, -0.27, log N(Si II) greater than 13.70, log N(S II) greater than 15.76, log N(Ge II) = 12.20 +0.09,-0.11, and log N(N v) = 14.06 +/- 0.02. Assuming solar reference abundances, the diffuse clouds containing Mg, S, and Ge along the sight line have average logarithmic depletions D(Mg) = -0.6 +/- 0.3 dex, D(S) greater than -0.2 dex, and D(Ge) = -0.2 +/- 0.2 dex. The Mg and Ge depletions are approximately 2 times smaller than is typical of diffuse clouds in the solar vicinity. Galactic rotational modeling of the N v profiles indicates that the highly ionized gas traced by this ion has a scale height of approximately 1 kpc if gas at large z-distances corotates with the underlying disk gas. Rotational modeling of the Si iv and C iv profiles measured by the IUE satellite yields similar scale height estimates. The scale height results contrast with previous studies of highly ionized gas in the outer Milky Way that reveal a more extended gas distribtion with h approximately equals 3-4 kpc. We detect a high-velocity feature in N v and Si II v(sub LSR) approximately equals + 125 km/s) that is probably created in an interface between warm and hot gas.

Sembach, Kenneth R.↗

NASA NTRS1992

Local distribution of old neutron stars

The local distribution of old disk neutron stars is approximated with a 1D model, in which the steady state distribution in the direction perpendicular to the Galactic plane is calculated, assuming a variety of the initial radio pulsar positions and velocities, and various Galactic potentials. It is found that the local distribution of old neutron stars is dominated by those that were born with very low velocities. The high-velocity neutron stars spend most of their lifetime far in the Galactic halo and do not contribute much to the local density. Therefore, the rms velocity at birth is not a good indicator of the scale height of the old population. The most likely half-density scale height for the old disk neutron stars is approximately 350 pc, the same as for the old disk G, K, and M stars. If gamma-ray bursts originate on old disk neutron stars, then 350 pc should also be the scale height for the bursters.

Frei, Szolt↗

NASA NTRS1973

Venus - Composition and structure of the visible clouds

It is proposed that the visible cloud deck on Venus is composed of droplets of sulfuric acid. These are formed by the very rapid photooxidation of carbonyl sulfide in the upper atmosphere. The clouds are best described as an extensive haze since the predicted particulate scale height probably exceeds the gas scale height within the layer. The predicted mixing ratio for water is .000001 (lower limit), and for both carbonyl sulfide and sulfur dioxide it is .0000001 (upper limit); these are in good agreement with observations. Gaps in the layer are not possible unless the planetary scale dynamics produce cloud turnover times of less than a few days. Under these conditions, the water mixing ratio could approach .0001, and the formation of a thin hydrochloric acid haze at high altitude above the main cloud is possible.

Prinn, R. G.↗

NASA NTRS1985

The extent of the local hi halo

Forty-five high-latitude, OB stars have been observed in the Ly alpha and 21 cm lines of HI in an effort to map out the vertical distribution and extent of the local HI halo. The 25 stars for which a reliable HI colum density can be obtained from Ly alpha lie between 60 and 3100 pc from the plane. The principal result is that the total column density of HI at z 1 kpc is, on the average, 5 + or - 3 x 10 the 19th power/sq cm, or 15% of the total sub HI. At relatively low z the data toward some stars suggest a low effective scale height and fairly high average foreground density, while toward others the effective scale height is large and the average density is low. This can be understood as the result of irregularities in the interstellar medium. A model with half of the HI mass in clouds having radii of a few pc and a Gaussian vertical distribution with sigma sub 2 = 135 pc, and half of the mass in an exponential component with a scale height of 500 pc, gives a satisfactory fit to the data. The technique of comparing Ly alpha and 21 cm column densities is also used to discuss the problem of estimating the distance to several possibly subluminous stars.

Lockman, F. J.↗

NASA NTRS1986

The extent of the local H I halo

Forty-five high-latitude, OB stars have been observed in the Ly alpha and 21 cm lines of HI in an effort to map out the vertical distribution and extent of the local HI halo. The 25 stars for which a reliable HI column density can be obtained from Ly alpha lie between 60 and 3100 pc from the plane. The principal result is that the total column density of HI at an absolute value of z greater than 1 kpc is, on the average, 5 + or - 3 x 10 to the 19th power/sq cm, or 15 percent of the total sub HI. At relatively low z the data toward some stars suggest a low effective scale height and fairly high average foreground density, while toward others the effective scale height is large and the average density is low. This can be understood as the result of irregularities in the interstellar medium. A model with half of the HI mass in clouds having radii of a few pc and a Gaussian vertical distribution with sigma sub 2 = 135 pc, and half of the mass in an exponential component with a scale height of 500 pc, gives a satisfactory fit to the data. The technique of comparing Ly alpha and 21 cm column densities is also used to discuss the problem of estimating the distance to several possibly subluminous stars.

Lockman, F. J.↗

NASA NTRS1994

Comparison of theories for gravity wave induced fluctuations in airglow emissions

A comparison is undertaken of theories for the gravity wave induced fluctuations in the intensity of airglow emissions and the associated temperature of the source region. The comparison is made in terms of Krassovsky's ratio eta(sub E) for a vertically extended emission region (eta(sub E) is the ratio of the vertically integrated normalized intensity perturbation to the vertically integrated intensity-weighted temperature perturbation). It is shown that the formulas for eta(sub E) in the works by Tarasick and Hines (1990) and Schubert et al. (1991) are in agreement for the case of an inviscid atmosphere. The calculation of eta(sub E) using the theory of Tarasick and Hines (1990) requires determination of their function chi; we show that chi is simply related to the 'single-level' Krassovsky's ratio eta of Schubert et al. (1991). The general relationship between chi and eta is applied to a simple chemical-dynamical model of the O2 atmospheric airglow and the altitude dependence of these quantities is evaluated for nonsteady state chemistry. Though the Tarasick and Hines (1990) formula for eta(sub E) does not explicitly depend on the scale heights of the minor constituents involved in airglow chemistry, eta(sub E) implicitly depends upon these scale heights through its dependences on chemical production and loss contained in chi. We demonstrate this dependence of eta(sub E) for the OH nightglow on atomic oxygen scale height by direct numerical evaluation of eta(sub E) in this case the dependence originates in the chemical production of perturbed ozone.

Walterscheid, R. L.↗

NASA NTRS1990

The distribution of interstellar Al III away from the Galactic plane

IUE spectra are analyzed to study the density distribution of interstellar Al III away from the Galactic plane. In most cases, the measured values of the relative line strengths are consistent with only modest levels of line saturation. Al III is found to have an exponential scale height and 1 sigma errors of 1.02(+0.36, -0.24) kpc. For the same set of 70 stars, the scale height and 1 sigma errors for H I are 0.67(+0.21, -0.16) kpc. The Al III scale height is similar to the value obtained for free electrons from pulsar dispersion measures. The ionized gas traced by Al III is somewhat more extended than the neutral gas traced by H I but less extended than the very highly ionized gas traced by Si IV, C IV, and N V.

Savage, Blair D.↗

NASA NTRS1976

The relationship between the galactic matter distribution, cosmic ray dynamics, and gamma ray production

Theoretical considerations and analysis of the results of gamma ray astronomy suggest that the galactic cosmic rays are dynamically coupled to the interstellar matter through the magnetic fields, and hence the cosmic ray density should be enhanced where the matter density is greatest on the scale of galactic arms. This concept has been explored in a galactic model using recent 21 cm radio observations of the neutral hydrogen and 2.6 mm observations of carbon monoxide, which is considered to be a tracer of molecular hydrogen. The model assumes: (1) cosmic rays are galactic and not universal; (2) on the scale of galactic arms, the cosmic ray column (surface) density is proportional to the total interstellar gas column density; (3) the cosmic ray scale height is significantly larger than the scale height of the matter; and (4) ours is a spiral galaxy characterized by an arm to interarm density ratio of about 3:1.

Kniffen, D. A.↗

NASA NTRS1977

SAS-2 gamma-ray results from the galactic plane and their implications for galactic structure and galactic cosmic-ray dynamics

The final SAS-2 results related to high energy galactic gamma-ray emission show a strong correlation with galactic structural features seen at other wavelenghts, when the known gamma-ray sources are subtracted. Theoretical considerations and analysis of the gamma-ray data suggest that the galactic cosmic rays are dynamically coupled to the interstellar matter through the magnetic fields, and hence the cosmic ray density is enhanced where the matter density is greatest on the scale of the galactic arms. This concept has been explored in a galactic model that assumes: (1) cosmic rays are galactic and not universal; (2)on the scale of the galactic arms, the cosmic ray column (surface) density is proportional to the total interstellar gas column density; (3)the cosmic ray scale height is significantly larger than the scale height to the matter; and (4) ours is a spiral galaxy characterized by an arm to interarm density ratio of over 2:1.

Fichtel, C. E.↗

NASA NTRS2022

Persistent Layers of Enhanced Gravity Wave Dissipation in the Upper Mesosphere Revealed From SABER Observations

Dissipation of gravity waves (GWs) and resultant momentum flux deposition and eddy diffusion significantly influence the atmospheric structure and circulation. Using the temperature profiles measured by the SABER instrument (2002–2021), we derive the global GW action and its scale height (HAm). Comparing to the background scale height (H), we identify a persistent layer of enhanced GW dissipation (HAm/H > 2) in the upper mesosphere. The enhanced dissipation is primarily centered at 80–85 km with a vertical range of ∼8–20 km. At middle and high latitudes, the enhanced dissipation extends down to ∼60 km and is located above the eastward (westward) wind peak in winter (summer). At low latitudes, enhanced dissipation occurs around the wind reversals. The possible mechanisms of enhanced dissipation include wave refraction, wind filtering, and reduced static stability. The persistent layer of enhanced dissipation identified here provide observational evidence for GW dissipation constrains in models.

gravity waves↗

NASA NTRS2020

Coronagraphic Observations of the Lunar Sodium Exosphere 2018-2019

Remote observations of the lunar sodium corona have been obtained with the Goddard Lunar Coronagraph located at the Winer Observatory in Sonoita, Arizona. We previously reported the results of observations in the spring, 2017, observing season (Killen et al., 2019). We report herein the results of the 2018–2019 observing campaign. We show definitive effects on the corona - the extended lunar sodium exosphere above 150 km from the surface - of enhanced ion flux onto the Moon as measured by the ARTEMIS ElectroStatic Analyzer. The three observations in this dataset with the largest column abundances are associated with entrance of the Moon into the magnetosheath. The enhancement in the exosphere due to ion flux is not long-lived after the enhanced ion influx decreases, confirming the findings of Killen et al., 2012. The column abundance is greatest at both the dawn and dusk terminators as predicted and simulated by Smyth and Marconi, 1995. The cause of the increased scale height at the terminators is consistent with radiation pressure acceleration anti-sunward. We report a shallow decline of column abundance with increasing latitude which is also consistent with radiation pressure acceleration. Most of our measured scale heights are on the order of 800–1800 km, increasing at high latitudes, consistent with the data set published in Killen et al., 2019. Although the intensity extrapolated to the surface decreases with latitude, the scale height increases with latitude, so that the exospheric column decreases more slowly with increasing latitude than does a cosine function.

moon↗

NASA NTRS1983

High altitude Venus haze from Pioneer Venus limb scans

High-resolution limb scans of Venus made with the Orbiter Cloud Photopolarimeter aboard Pioneer Venus have been used to observe the high altitude Venus haze and its variation over almost one half a Venusian year. A model for a spherical atmosphere with tangential viewing geometry was used to analyze the observations and derive the haze properties. Values are found for the particle size and refractive index, particle number density and scale height, and eddy diffusion coefficient. Single scattering computations show good agreement with observed intensities for particles smaller than 0.3 micron radius and refractive index less than 1.7, consistent with, but not limited to, concentrated sulfuric acid. Particle scale height in the 0.5 to 2 mbar pressure regions varies between 1 and 3 km over the season, latitude, and local time ranges of the observations. Detached layers of haze are sometimes present. An average particle scale height of 2.2 km at 84 km altitude yields an eddy diffusion coefficient of 130,000 sq cm/sec.

Lane, W. A.↗

NASA NTRS1972

The occultation of beta Scorpii by Jupiter and Io. I - Jupiter.

Use of computer-controlled one-dimensional area-scanning photometers to observe the occultation of the Beta Scorpii system by Jupiter on May 13, 1971. Six high-quality light curves were obtained; three of the occultations of the brighter component Beta Sco A and three of Beta Sco C. The mean scale height of the Jovian upper atmosphere is 32 plus or minus 6 km near -10 deg zenographic latitude, 31 plus or minus 2 km at -47 deg zenographic latitude, and 24 plus or minus 2 km at -57 deg zenographic latitude. The determination of the atmospheric scale height is highly sensitive to the background level subtracted, providing a possible explanation of an earlier result by Baum and Code (1953) placing the scale height at about 8 km. Correlated departures of the light curve from a theoretical isothermal curve are reproduced in the three bright-star curves, and are thus not due to random density fluctuations in the Jovian atmosphere, but are rather due to global stratification. Details of the stratification, which includes at least a number of warm layers, are examined by deconvolution of the light curves. There is evidence for a high-temperature (T greater than 300 K) thermosphere on two of the bright-star light curves.

Hubbard, W. B.↗