NASA Scientific and Technical Aerospace Reports

perigee observations from 1 December 1997 to 30 November 1998 shows that the Polar perigee passes evenly covered the
southern polar cap region, while the O(+) density trough was always located on the nightside portion of the polar cap
magnetosphere/ionosphere, and that invariant latitude spans of such troughs could be as large as 23 deg. in extent. The trough
occurrence displayed a strong seasonal dependence; in the winter season (e.g., for July in the Southern Hemisphere) the O(+)
ion density trough occurrence frequency ranged up to 92%, while in the summer season (e.g., for January in the Southern
Hemisphere) it decreased to as low as 15%. Our statistical results show that the trough occurrence was generally anticorrelated
with solar wind dynamic pressure in the solar wind dynamic pressure range 0.8 - 2.6 nanopascal. The O(+) ion density trough
occurrence appeared relatively independent of the geomagnetic Kp index, IMF Bz, and By conditions. However, as suggested
by the seasonal dependence, the O(+) ion density trough occurrence was strongly related to the solar zenith angle (SZA). In
the SZA range 50 deg. to 125 deg., the trough occurrence increased monotonically with SZA. In addition, we sought to
determine consistent density and velocity signatures at lower altitudes associated the O(+) ion density trough at 5000 km by
examining the near-simultaneous O(+) densities and vertical velocities observed by the DMSP satellite group orbiting at 840
km altitude. However, consistent correlations between the dual altitudes were not reliably established from the present
examinations.
Author
Oxygen Ions; Density; Polar Caps; Altitude; Dynamic Pressure; Ion Density (Concentration); Solar Wind
20040071148 American Astronomical Society, USA
The BATSE Earth Occultation Catalog of Low Energy Gamma-Ray Sources
Harmon, B. A.; Wilson-Hodge, C. A.; Fishman, G. J.; Paciesas, W. S.; Zhang, S. N.; Finger, M. H.; Connaughton, V.; Koshut,
T. M.; Henze, W.; McCollough, M. L., et al.; American Astronomical Society; [2004]; Vol. 33, pp. 1496; In English; 199th
AAS Meeting, [2004], unknown
Contract(s)/Grant(s): NAG5-7927; No Copyright; Avail: Other Sources; Abstract Only
The Burst and Transient Source Experiment (BATSE),aboard the COmptOn Gamma Ray Observatory (CGRO), provided
a record of the hard X-ray/low energy gamma ray sky between April 1991 and June 2000. During that time, a catalog of known
sources was derived from existing catalogs such as HEAO A-4 (Levine et al. 19841, as well as new transient sources
discovered with RATSE and other X-ray monitors operating in the CGRO era. The Earth Occultation Technique (Harmon et
al. 2001, astro-ph/0109069) was used to monitor a combination of these sources, mostly galactic, totaling about 175 objects.
The catalog will present the global properties of these sources and their probability of detection (>lO mCrab, 20-100
keV) with BATSE. Systematic errors due to unknown sources or background components are included. Cursory analyses to
search for new transients (35-80 mCrab in the 20-100 keV band) and super-orbital periods in known binary sources are also
presented. Whole mission light curves and associated data production/analysis tools are being delivered to the HEASARC for
public use.
Author
Catalogs (Publications); Gamma Ray Bursts
20040074195 City Univ. of Hong Kong, Kowloon, Hong Kong
A New Method to Use Chandra Data to Resolve the X-Ray Halos Around Point Sources and Its Application to Cygnus
X-1
Yao, Y.; Zhang, S. Nan; Zhang, X. L.; Feng, Y. X.; May 2003; 1 pp.; In English; American Astronomical Society Meeting
202, May 2003
Contract(s)/Grant(s): NAG5-7927; Copyright; Avail: Other Sources; Abstract Only
The excellent angular resolution, good energy resolution and broad energy band make Chandra ACIS the best instrument
for studying the X-ray halos around some galactic x-ray point sources caused by the dust scattering of X-rays in the interstellar
medium, but direct images of bright sources of b rightsources obtained with ACIS usually from severe pile- UP - Making
use of the fact that an isotropic image could be reconstructed from it’s projection on any direction, we can reconstruct the
images of the X-ray halos from data obtained with the regular HETGS and/or the CC mode. With the reconstructed high
resolution images, we can probe the X-ray halos as close as 1 arcsecond to their associated point sources.
Author (revised)
Interstellar Matter; Image Analysis; Halos; Galactic Radiation
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