Comparison of the Nimbus-4 BUV ozone data with the Ames two-dimensional model

A comparison is made of the first two years of Nimbus 4 backscattered ultraviolet (BUV) ozone measurements with the predictions of the Ames two dimensional model. The ozone observations used consist of the mixing ratio on the 1, 2, 5, and 10 mb pressure surfaces. The data are zone and time averaged to obtain seasonal means for 1970 and 1971 and are found to show strong and repeatable meridional and seasonal dependencies. The model used for comparison with the observations extends from 80 N to 80 S latitude and from altitudes of 0 to 60 km with 5 deg horizontal grid spacing and 2.5 km vertical grid spacing. Chemical reaction and photolysis rates are diurnally averaged and the photodissociation rates are corrected for the effects of scattering. The large altitude, latitude, and seasonal changes in the ozone data agree with the model predictions. Model predictions of the sensitivity of the comparisons to changes in the assumed mixing ratios of water vapor, odd nitrogen, and odd chlorine, as well as to changes in the ambient temperature and transport parameters are also shown

Planetary Transits Toward the Galactic Bulge

The primary difficulty with using transits to discover extrasolar planets is the low probability a planet has of transiting its parent star. One way of overcoming this difficulty is to search for transits in dense stellar fields, such as the Galactic bulge. Here I estimate the number of planets that might be detected from a monitoring campaign toward the bulge. A campaign lasting 10 nights on a 10 meter telescope (assuming 8 hours of observations per night and a 5'x5' field of view) would detect about 100 planets with radius \rp=1.5 \rjup, or about 30 planets with \rp=1.0 \rjup, if the frequency and distribution of planets in the bulge is similar to that in the solar neighborhood. Most of these planets will be discovered around stars just below the turn-off, i.e. slightly evolved G-dwarfs. Campaigns involving 1- or 4-m class telescopes are unlikely to discover any planets, unless there exists a substantial population of companions with \rp > 1.5 \rjup.Comment: 4 pages, 4 figures. Submitted to ApJ Letter

Method of identifying clusters representing statistical dependencies in multivariate data

Approach is first to cluster and then to compute spatial boundaries for resulting clusters. Next step is to compute, from set of Monte Carlo samples obtained from scrambled data, estimates of probabilities of obtaining at least as many points within boundaries as were actually observed in original data

Proceedings of the Workshop on Improvements to Photometry

The purposes of the workshop were to determine what astronomical problems would benefit by increased photometric precision, determine the current level of precision, identify the processes limiting the precision, and recommend approaches to improving photometric precision. Twenty representatives of the university, industry, and government communities participated. Results and recommendations are discussed

Tests of a multichannel photometer based on silicon diode detectors

A breadboard photometer was constructed that demonstrates a precision of 2 times 10 to the 4th power in the laboratory and scintillation-limited performance when used with an 0.5 m aperture telescope. Because the detectors and preamps are not cooled, only stars with m sub v approx. less than 4 are bright enough to allow the photometer to attain a precision of 1 times 10 to the 3rd power for three minute observations with an 0.5 m aperature telescope. Cooling the telescope should allow much fainter stars to be observed. Increasing the aperture of the telescope will allow higher precision and the observation of fainter stars

Predictions of the electrical conductivity and charging of the cloud particles in Jupiter's atmosphere

The electrical conductivity and electrical charge on cloud particles ( composed of ammonia, ammonium hydrosulfide, and water) in the atmosphere of Jupiter are computed for pressures between 5.5 and 0.1 bars. The source of ionization is galactic cosmic rays (GCR). The distribution of charge among the various reservoirs is a function of altitude and the total area of the aerosol particles. For pressures below 4 bars, the electrons are scavenged efficiently by the cloud particles, decreasing the electron- ion recombination rate and resulting in increased positive ion abundance over that in the absence of the particles. For the upper regions of each cloud layer, the area of the aerosols and the large diffusion rate of the electrons cause most aerosol particles to be negatively charged. Near the bases of the cloud layers, the larger total area of the aerosols causes most of the charge, positive and negative, to reside on particles. Where clouds are present, the reduction of the electron conductivity ranges from a factor of 30 at 0.1 bar to 10 4 at 4 bars. At pressures near 1 bar and 4 bars, the positive ion conductivity increases by a factor of 10 over that expected for the clear atmosphere. A parametric study of negative ions shows that they are likely to be insignificant. For altitudes below the 0.3- bar level the predicted positive and negative conductivities are well below the detection limit of the relaxation and mutual impedance instruments such as those employed on the Huygens entry probe

Kepler-62: A Five-Planet System with Planets of 1.4 and 1.6 Earth Radii in the Habitable Zone

We present the detection of five planets—Kepler-62b, c, d, e, and f—of size 1.31, 0.54, 1.95, 1.61 and 1.41 Earth radii (R_⊕), orbiting a K2V star at periods of 5.7, 12.4, 18.2, 122.4, and 267.3 days, respectively. The outermost planets, Kepler-62e and -62f, are super–Earth-size (1.25 R_⊕ < planet radius ≤ 2.0 R_⊕) planets in the habitable zone of their host star, respectively receiving 1.2 ± 0.2 times and 0.41 ± 0.05 times the solar flux at Earth’s orbit. Theoretical models of Kepler-62e and -62f for a stellar age of ~7 billion years suggest that both planets could be solid, either with a rocky composition or composed of mostly solid water in their bulk

Two-dimensional model studies of the effect of supersonic aircraft operations on the stratospheric ozone content

For a fleet of 250 aircraft, the change in the ozone column is predicted to be very close to zero; in fact, the ozone overburden may actually increase as a result of show that above 25 to 30 km the ozone abundance decreases via catalytic destruction, but at lower heights it increases, mainly as a result of coupling with odd hydrogen species. Water vapor released in the engine exhaust is predicted to cause ozone decreases; for the hypothetical engines used in the study, the total column ozone changes due to water vapor emission largely offset the predicted ozone increases due to NOx emission. The actual effect of water vapor may be less than calculated because present models do not include thermal feedback. Feedback refers to the cooling effect of additional water vapor that would tend to slow the NOx reactions which destroy ozone