Search Publications
Digging deep for ice in Isidis Planitia—New constraints on subsurface volatile concentrations from thermal modeling
Helbert, J.; Benkhoff, J.
The Isidis Planitia region on Mars usually is regarded as a comparably attractive site for landing missions based on engineering constraints such as elevation and smooth regional topography. The Mars Express landed element Beagle 2 was deployed to this area, and the southern margin of the basin was selected as one of the backup landing sites for t…
On VI Asymmetry and an Accelerated Outflow in an Obscured Seyfert: FUSE and HST STIS Spectroscopy of Mrk 533
Hutchings, John; Whittle, Mark; Wills, Beverley J. +2 more
We present far-ultraviolet spectra of the Seyfert 2 galaxy Mrk 533 obtained with FUSE. These spectra show narrow asymmetrical O VI λλ1032,1038 emission lines with stronger wings shortward of the peak wavelength, but the degree of asymmetry of these wings in velocity is much lower than that of the wings of the lines of lower ionization. In the comb…
Measuring and understanding space turbulence
Belmont, Gérard; Rezeau, Laurence; Sahraoui, Fouad
For many physical issues including reconnection, the role of waves and turbulence is likely to be predominant in space physics. This role can be viewed as a natural consequence of the general properties of turbulence, but these properties, although widely recognized in hydrodynamics, are much less familiar in plasmas. The connections between the d…
Positron production and annihilation in the Milky Way
Prantzos, Nikos
SNIa in the Milky Way bulge may supply about 12% of the positrons required by observations of the 511 keV emission from the inner Galaxy, while positrons from disk SNIa may account for the totality of that emission. It is argued here that most of the disk positrons propagate away from the disk (due to the low density environment) and the resulting…
Modeling accelerated pick-up ion distributions at an interplanetary shock
Baring, Matthew G.; Summerlin, Errol J.
The acceleration of interstellar pick-up ions as well as solar wind species has been observed at a multitude of interplanetary (IP) shocks by different spacecraft. The efficiency of injection of the pick-up ion component differs from that of the solar wind, and is expected to be strongly enhanced at highly oblique and quasi-perpendicular shock eve…
Swift Observations of the Highly X-Ray Variable Narrow-Line Seyfert 1 Galaxy RX J0148.3-2758
O'Brien, Paul T.; Schady, Patricia; Leighly, Karen M. +4 more
We report on Swift observations of the narrow-line Seyfert 1 galaxy RX J0148.3-2758. It was observed for 41.6 ks in 2005 May and for 15.8 ks in 2005 December. On short as well as on long timescales, RX J0148.3-2758 is a highly variable source. It doubles its X-ray flux within 18-25 ks. The observation of 2005 December 9, which had a flux 4 times l…
The Astro-E2/XRS-2 helium insert system
Mitsuda, K.; Fujimoto, R.; McCammon, D. +5 more
The X-ray Spectrometer (XRS-2) instrument on the Japanese Space Agency (JAXA) Astro-E2 spacecraft will measure faint X-ray emissions in the energy range of 0.2-10 keV. A square array of 32 X-ray microcalorimeters used will be able to distinguish individual photons to better than 10 eV at 6 keV, with a quantum efficiency near 100%. The detectors ar…
Heliospheric ion energization due to emerging CME shocks
Bale, S. D.; Roth, I.
Formation of inhomogeneous electromagnetic structures with gradients in magnetic field and intrinsic electric fields is commonly observed in magnetized plasmas. Heliospheric plasmas are susceptible to formation of localized, supersonically propagating electromagnetic inhomogeneities. Coronal relaxation may result in an emergence close to solar sur…
Application of an orbital radar sounder model to detecting Martian polar subsurface features
Farrell, William M.; Xu, Yanbin; Cummer, Steven A.
A model to simulate the complete planetary orbital radar sounder problem is presented in this paper. The subsurface features and the ionosphere will not only bring ambiguity to the collected radar sounder data, but also critically affect instrument capabilities. These environmental uncertainties generate a compelling need for meaningful quantitati…
Wave acceleration of the fast solar wind
Ofman, Leon
Observations show that the solar wind exhibits two modes of outflow: the slow (∼400 km s -1), high density, highly variable wind that emerges from equatorial solar regions, and the high latitude, fast (∼800 km s -1), low density, steady solar wind. The bi-modal solar wind outflow is most evident near minima of solar activity.…