JOP162 Magnetic Field Evolution Around Leading Sunspots AUTHORS : Ted Tarbell (LMSAL), Yukio Katsukawa (NAOJ) VERSION : Draft (21 January 2003), Received 22 January 2003 INSTRUMENTS : ASP at NSO/Sacramento Peak, TRACE, CDS, MDI DATES: Telescope time is confirmed at Sac. Peak, March 9-20, 2003 SCIENTIFIC OBJECTIVE : We propose to observe the evolution and properties of vector magnetic fields of active regions with the Advanced Stokes Polarimeter (ASP) at Sac Peak. The primary target in this observing run is magnetic fields around well-developed leading sunspots, where photospheric magnetic features, such as moving magnetic features (MMFs) and satellite spots, may produce enhanced coronal activities. Simultaneous observations with TRACE and SoHO provide us coronal features associated with the magnetic fields at the photosphere. We expect that this project will give us clues to clarify the causal relation between the photospheric magnetic signatures and the coronal activities. The research is also regarded as a preview of science with the spectro-polarimeter aboard the Solar-B optical telescope. SCIENTIFIC JUSTIFICATION : The primary objective of this project is to understand vector magnetic fields responsible for enhanced activities and quasi-steady heating well observed in the corona. In this observing run, we will focus on magnetic fields around well-developed leading sunspot in active regions, where remarkable features are well observed in the corona. Yohkoh soft X-ray observations show that microflares have preferred locations around leading sunspots (Shimizu 1993). TRACE and EIT observations demonstrate that some quasi-steady EUV loops ("fan"-like loops) are rooted into around leading spots. TRACE has found "moss" features there, which may be associated with footpoints of high-temperature Yohkoh loops. At the photosphere, moving magnetic features (MMFs) and the formation of satellite spots are well observed, and they may be possible origins of microflares. In the observing run, the observing target of Advanced Stokes Polarimeter (ASP) at Sacrament Peak will be coordinated with observations of TRACE and SoHO CDS and MDI. ASP will provide precise measurements of vector magnetic and Doppler velocity fields, and MDI will provide the evolution of the magnetic fields with high cadence. Using the acquired data, we plan to study the following topics; 1) How is the magnetic-field evolution related to the occurrence of microflares? 2) How are the photospheric magnetic properties (e.g., currents and helicity injection) related to the resultant energy dissipation into the corona? 3) How are twisted or helical magnetic structures responsible for coronal activities and heating? For this investigation, we plan to numerically estimate magnetic fields in the corona with accurate measurement of photospheric magnetic fields. ASP observations coordinated with Yohkoh, SoHO and TRACE were successfully performed in 13-22 November 2000 and 8-23 April 2002. The observations mainly focused on day-by-day evolution of photospheric magnetic fields and their associated coronal features for entire active regions. The data has been deeply analyzed by three graduate students at the University of Tokyo. Masahito Kubo studies magnetic and velocity fields of the well-developed active region observed in November 2000; his master thesis with this study was accepted to the University of Tokyo on March 2002. Yasushi Sakamoto has developed the calculation scheme of magnetic helicity injection rate and will submit his master thesis by January 2003. Yukio Katsukawa is studying magnetic properties at the footpoints of coronal loops. OPERATIONAL CONSIDERATIONS : Selection of the target active region will be made one or more days in advance to allow TRACE timeline preparation as usual. Active regions near central meridian are preferred to minimize projection effects, and following the same region for several days in a row is generally desirable. The TRACE field of view will cover the entire region. The ASP field of view is 150 x 90 arcsec maximum, but will often be smaller to speed up the cadence, depending on the region. The detailed pointing within the active region and field size for ASP will be chosen using TRACE and/or ground-based images early in the morning each day, and sent to the CDS planner by email before 15 UT. The hours of Sac. Peak observation will be approximately 15 - 23 UT (TBC), with the best conditions probably between 16 - 20 UT. OBSERVING SEQUENCES : NSO/Sac Peak -- The ASP will run at its highest cadence, typically making a map every few tens of minutes. If possible, the Universal Birefringent Filter system will be used for simultaneous chromospheric images. TRACE -- High quality, medium cadence 171 images are the primary observation, with frequent context images in white light and 1600 A, and occasional context in 195 desired. The TRACE planner will decide the frequency of quadrant changes based on recent experience and the station pass schedule. TRACE 171 observations of the same region overnight will be useful for precise targeting of the ASP each morning. CDS [NIS] - A standard active region diagnostic study with spatial resolution 4'' x 3.4'' is requested. This records several bright lines covering temperatures from 10^5 to 2x10^6 K and some density diagnostic lines. Note that the density diagnostics require careful analysis due to line blending. Coverage of the entire active region, or at least a large part of it including the ASP field, is desired. MDI -- If the AR is in the high-resolution field of view then high resolution observations (magnetograms, velocities and continuum filtergrams) are desired. If not, then only full disk magnetograms are sufficient.