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Effect of Flow-Tube Geometry on Solar Wind Properties
Chen, Y.; Hu, Y. Q.
A mathematical description of the solar wind flow-tube geometry is proposed. The expansion factor of the flow tube f(r) (=a/r2, r is the heliocentric distance and a is the flow-tube cross-section area)increases monotonically from 1 at the coronal base to m at rc, and approaches its asymptotic value f∞ ne…
HST Observations of Sakurai's Object (V4334 Sgr) and Related Stars
Bond, Howard E.; Pollacco, Don L.
We describe our ongoing program of HST observations of Sakurai's Object(V4334 Sgr). Direct WFPC2 imaging from August 1996 through August 2000 revealsno transient features (such as light echoes), and documents the decline of thestar to below 24th visual magnitude in 2000. The surrounding planetary nebulahas shown no changes from 1996 through 2000. …
Transition region and coronal plasmas: instrumentation and spectral analysis
Dammasch, Ingolf E.; Wilhelm, Klaus; Hassler, Donald M.
The plasma conditions in the solar atmosphere and, in particular, in coronal holes are summarized, before space-borne instrumentation for observing these regions in vacuum-ultraviolet light is briefly introduced with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on the Solar and Heliospheric Observatory (SOHO) as exa…
SOHO, Yohkoh, Ulysses and Trace: The four solar missions in perspective, and available resources
Domingo, V.
Four solar observing spacecraft, now in operation, have obtained and continue to obtain data during the late phase of solar cycle 22 and hopefully most of cycle 23. The data are available for scientific analysis, practically in an unrestricted manner. A large pool of software suited for the processing and to help programming any data analysis is f…
Systematic Errors of High–Precision Photometric Catalogues
Mironov, Aleksey; Zakharov, Andrey
A very accurate imitation of Hipparcos and Tycho Hp, BT, andVT magnitudes was made using W, B, V, R magnitudes from the Tien Shan photometric catalogue. The calculated magnitudes were compared to the observed ones. It is shown that there are systematic differences between calculated and observed magnitudes. The systematic err…
Star Formation and Dust Extinction in Nearby Star Forming and Starburst Galaxies
Buat, Veronique
We study the star formation rate and dust extinction properties of a sample of nearby star forming galaxies as derived from Halpha and UV (2000 A) observations and we compare them to those of a sample of starburst galaxies. The dust extinction in Halpha is estimated from the Balmer decrement and the extinction in UV using the FIR to UV flux ratio …