Physical Properties of a 2003 April Quiescent Streamer

Abstract

In 2003 April, the Ultraviolet Coronagraph Spectrometer (UVCS) on board the Solar and Heliospheric Observatory (SOHO) observed a quiescent streamer in an effort to derive the physical plasma parameters across the streamer and as a function of height ( from 1.75 to 5.0 R-circle dot). Values for the electron temperature, proton and O5+ kinetic temperatures, elemental abundances, and O5+ outflow velocity were derived. The presence of the first ionization potential (FIP) effect was also explored. These plasma parameters were compared to those derived for other previously reported active region and quiescent streamers. The photospheric normalized absolute elemental abundances for O, Si, S, Ar, and Fe were derived at 1.75 R-circle dot. The remaining parameters were derived at five heights up to 5.0 R-circle dot. To calculate the electron density above 2.2 R-circle dot the polarized brightness data from another SOHO instrument, the Large Angle Spectroscopic Coronagraph (LASCO) C2 detector, was employed. The streamer was located above a complex filament structure and had a slightly higher electron temperature compared to what is typically found for quiescent streamers. This streamer did exhibit the customary FIP effect, but no abundance-depleted core typically found for such stable quiescent streamers was detected. The perpendicular kinetic temperature for the protons and the O5+ ions did not vary across the streamer. This differs from two other quiescent streamer comparison cases, in which the O5+ kinetic temperature did decrease at the core structure. The O5+ outflow velocities were similar to those observed in an equatorial streamer from solar minimum.