Jet Propulsion Laboratory

About: Jet Propulsion Laboratory is a facility organization based out in La Cañada Flintridge, California, United States. It is known for research contribution in the topics: Mars Exploration Program & Telescope. The organization has 8801 authors who have published 14333 publications receiving 548163 citations. The organization is also known as: JPL & NASA JPL.

Grid turbulence at large Reynolds numbers.

Abstract: Grid turbulence for large Reynolds numbers, noting consistency of power spectra values with Kolmogoroff scaling, decay law and Reynolds number effect on turbulence

Spectrum of a habitable world: earthshine in the near-infrared

Abstract: To characterize the spectrum of Earth viewed as an extrasolar planet, we observed the spatially integrated near-infrared (0.7-2.4 μm) reflection spectrum of Earth via the dark side of the Moon (earthshine). After contributions from the Sun, Moon, and local atmosphere were removed, the resulting spectrum was fitted with a simple model of the reflectivity of Earth. The best model fit is dominated by the reflection spectrum of the atmosphere above medium-altitude water clouds, with lesser contributions from high-altitude ice clouds and from the ground. The spectral features seen are H2O (six strong band structures from 0.7 to 2.0 μm), CO2 (six moderate-strength features from 1.4 to 2.1 μm), O2 (two moderate-strength features at 0.76 and 1.26 μm), and several weak CH4 features. Interpreted as a spectrum of an extrasolar planet, we would confidently conclude that this is a habitable planet, based on the presence of strong water bands. Furthermore, the simultaneous presence of oxygen and methane is a strong indicator of biological activity. We might also conclude that the planet is geologically active, based on the presence of CO2, water, and a dynamic atmosphere (inferred from cirrus clouds, cumulus clouds, and clear-air fractions in our model fit). This suggests that it would be valuable for the Terrestrial Planet Finder-Coronagraph (TPF-C) mission to include near-infrared spectroscopy capability. On the basis of the present work, we suggest that future long-term monitoring of the earthshine would allow us to discern how the globally integrated spectrum changes with planet rotation, cloud cover, and seasons.

General relativistic simulations of early jet formation in a rapidly rotating black hole magnetosphere

Abstract: To investigate the formation mechanism of relativistic jets in active galactic nuclei and microquasars, we have developed a new general relativistic magnetohydrodynamic code in Kerr geometry. Here we report on the —rst numerical simulations of jet formation in a rapidly rotating (a \ 0.95) Kerr black hole magnetosphere. We study cases in which the Keplerian accretion disk is both corotating and counter- rotating with respect to the black hole rotation, and investigate the —rst D50 light-crossing times. In the corotating disk case, our results are almost the same as those in Schwarzschild black hole cases: a gas pressuredriven jet is formed by a shock in the disk, and a weaker magnetically driven jet is also gener- ated outside the gas pressuredriven jet. On the other hand, in the counter-rotating disk case, a new powerful magnetically driven jet is formed inside the gas pressuredriven jet. The newly found magneti- cally driven jet in the latter case is accelerated by a strong magnetic —eld created by frame dragging in the ergosphere. Through this process, the magnetic —eld extracts the energy of the black hole rotation. Subject headings: accretion, accretion disksblack hole physicsgalaxies: jetsmagnetic —elds ¨ methods: numericalMHDrelativity

Large Structures and Galaxy Evolution in COSMOS at z < 1.1*

Abstract: We present the first identification of large-scale structures (LSSs) at z 2), compared to the lower mass galaxies there. Over the range z < 1.1, we do not see evolution in the mass of galaxies by more than a factor of ~2 separating active and inactive star-forming galaxy populations.