Search Publications
Missions
Journals
Publication Years
Titan's Atmospheric Temperatures, Winds, and Composition
Strobel, D. F.; Showalter, M. R.; Lellouch, E. +42 more
Temperatures obtained from early Cassini infrared observations of Titan show a stratopause at an altitude of 310 kilometers (and 186 kelvin at 15°S). Stratospheric temperatures are coldest in the winter northern hemisphere, with zonal winds reaching 160 meters per second. The concentrations of several stratospheric organic compounds are enhanced a…
An upper limit to the masses of stars
Figer, Donald F.
There is no accepted upper mass limit for stars. Such a basic quantity eludes both theory and observation, because of an imperfect understanding of the star-formation process and because of incompleteness in surveying the Galaxy. The Arches cluster is ideal for investigating such limits, being large enough to expect stars at least as massive as ~5…
Reflections of Active Galactic Nucleus Outbursts in the Gaseous Atmosphere of M87
Churazov, E.; Vikhlinin, A.; Forman, W. +7 more
We combined deep Chandra, ROSAT HRI, and XMM-Newton observations of M87 to study the impact of active galactic nucleus (AGN) outbursts on its gaseous atmosphere. Many X-ray features appear to be a direct result of repetitive AGN outbursts. In particular, the X-ray cavities around the jet and counterjet are likely due to the expansion of radio plas…
The Foreshock
Eastwood, J. P.; Lucek, E. A.; Narita, Y. +4 more
Solar Wind Origin in Coronal Funnels
Wilhelm, Klaus; Marsch, Eckart; Wang, Jing-Xiu +4 more
The origin of the solar wind in solar coronal holes has long been unclear. We establish that the solar wind starts flowing out of the corona at heights above the photosphere between 5 megameters and 20 megameters in magnetic funnels. This result is obtained by a correlation of the Doppler-velocity and radiance maps of spectral lines emitted by var…
Helioseismological Implications of Recent Solar Abundance Determinations
Pinsonneault, Marc; Basu, Sarbani; Bahcall, John N. +1 more
We show that standard solar models are in good agreement with the helioseismologically determined sound speed and density as a function of solar radius, the depth of the convective zone, and the surface helium abundance, as long as those models do not incorporate the most recent heavy-element abundance determinations. However, sophisticated new an…
Rapid Compton-thick/Compton-thin Transitions in the Seyfert 2 Galaxy NGC 1365
Zezas, A.; Elvis, M.; Baldi, A. +2 more
We present multiple Chandra and XMM-Newton observations of the type 1.8 Seyfert galaxy NGC 1365, which shows the most dramatic X-ray spectral changes observed so far in an active galactic nucleus: the source switched from reflection-dominated to transmission-dominated and back in just 6 weeks. During this time the soft thermal component, arising f…
Composition and Dynamics of Plasma in Saturn's Magnetosphere
Lewis, G. R.; Coates, A. J.; Linder, D. R. +40 more
During Cassini's initial orbit, we observed a dynamic magnetosphere composed primarily of a complex mixture of water-derived atomic and molecular ions. We have identified four distinct regions characterized by differences in both bulk plasma properties and ion composition. Protons are the dominant species outside about 9 RS (where R
An Ab Initio Approach to the Solar Coronal Heating Problem
Nordlund, Åke; Gudiksen, Boris Vilhelm
We present an ab initio approach to the solar coronal heating problem by modeling a small part of the solar corona in a computational box using a three-dimensional MHD code including realistic physics. The observed solar granular velocity pattern and its amplitude and vorticity power spectra, as reproduced by a weighted Voronoi tessellation method…
Making the Corona and the Fast Solar Wind: A Self-consistent Simulation for the Low-Frequency Alfvén Waves from the Photosphere to 0.3 AU
Inutsuka, Shu-ichiro; Suzuki, Takeru K.
By performing a one-dimensional magnetohydrodynamic simulation with radiative cooling and thermal conduction, we show that the coronal heating and the fast solar wind acceleration in the coronal holes are natural consequences of the footpoint fluctuations of the magnetic fields at the photosphere. We initially set up a static open flux tube with a…