Active Region Streamer Diagnostics 2001 September 14–16

Abstract

From 2001 September 14 to 16 the Ultraviolet Coronal Spectrometer aboard the Solar and Heliospheric Observatory conducted a series of observations designed to study the absolute elemental abundances of an active region streamer. The absolute elemental abundances for O, Si, Fe, Mg, N, S, and Ar were calculated utilizing a constant electron temperature technique and an alternative approach to the emission measure technique, both producing complementary results. The manifestation of the first ionization potential (FIP) effect was observed here as in previous streamers. Two aspects of this streamer make it unusual and worth special attention. The active region streamer observed possessed an abundance-depleted core typically, although not exclusively, seen in quiescent streamers. A coronal mass ejection (CME) occurred at the active region during the observations. This event resulted in the second unexpected aspect of this streamer, its quick return to the same general abundance characteristics that existed before the CME occurred. The re-formation of a depleted core and the presence of the FIP effect immediately after a highly disruptive event are surprising given the 1 day timescale predicted by streamer theories.