JOP 151 Active Region Streamer Study Version: Dec. 19, 2001 Authors: Yuan-Kuen Ko, John Raymond (SOHO/UVCS) Andrzej Fludra (SOHO/CDS) Jing Li (Yohkoh/SXT) Participating Instruments: SOHO/UVCS, SOHO/CDS, Yohkoh/SXT, SOHO/EIT, SOHO/MDI, SOHO/LASCO Proposed Dates: First run: Jan.3 - 10, 2002 Second run: Jan.22 - Feb.3, 2002 Scientific Objective: The objective of this JOP is to study the electron temperature and elemental abundances in the corona above a sample of active regions with different appearance and magnetic properties (e.g. size, sunspot number and configuration). We plan to study these physical properties as a function of height and to investigate if there is any correlation with other properties of the active regions. Justification: The active regions, including limb active regions, have been a frequent target for SOHO JOPs and Campaigns. However, there has not been one to systematically study their physical properties, namly electron temperature and elemental abundances, in the corona as a function of height up to 1.6 Ro or even higher. Previous UVCS observations have indicated that the relative intensity of the lines of different formation temperature can be quite different among different active regions. One UVCS analysis on an active region streamer has shown that the elemental abundances decrease with height between 1.2 and 1.6 Ro. These physical properites in the corona may be closely associated with the properties of the underlying active region, such as its size and magnetic configuration. This JOP is aimed at understanding the possible relationship among these active region properties, not only in the loops close to 1 Ro, but also their extension into the corona up to 1.9 Ro. Instrument Plans: 1) SOHO/UVCS: The daily target is an active region at the limb. UVCS slit is 40 arcmin long which covers position angle of 57 degrees at 1.6 Ro, or 52 degrees at 1.9 Ro. The grating positions are chosen to observe a broad range of lines in several ionization stages for electron temperature analysis. The lines consist of both low-FIP and high-FIP elements. We expect to derive the absolute abundances of N, O, Mg, Si, S, Ar, K, Ca, Fe, Ni. Each observing sequence is 10 hours long. The mechanism settings are: Observing heights: 1.6 or 1.9 Ro (Xtalk correction included) Occulter: 1.5 mm over-occulting OVI channel slit: 100 um OVI channel detector mask: msk_000303_OVI OVI channel grating positions: 103000, 184200, 225000, 236700 2) SOHO/CDS: CDS will run ARDIAG_2 study, in a mosaic of several rasters covering the limb and the bright AR emission above the limb. One raster duration is 1 h 25 min, up to 8 rasters may be used. 20 spectral windows include a wide selection of transition region and coronal lines providing temperature diagnostics. Abundances of Fe, Si, Ca, Ne, Mg and O can be derived. 3) Yohkoh/SXT: The SXT general full disk observations with filter pair Al.1/AlMg will be used to derive the electron temperature and emission measure in the corona at the limb from 1 Ro up to maximum height of 1.5 Ro. It bridges the analysis of the corona between CDS and UVCS field of view. We understand that Yohkoh/SXT participation is contigent upon the recovery status of Yohkoh by the proposed run dates. 4) SOHO/EIT: Normal cadence full disk EIT 195 images will be used for target selection. 5) SOHO/MDI: Full disk MDI intensitygrams and magnetograms will be used for target selection as we plan to sample active regions of various magnetic configurations. 6) SOHO/LASCO, LASCO C2 images will be used to demonstrate the manifestation of these active regions in the white light corona above 2 Ro.