SOTSP: HOP315 (AR flows and fields)
2016-09-24T14:34:00 to 2016-09-24T14:54:00
Science Goal: Short-term Active Region Evolution
Program: Fast map 64x122", 1-side, Q75
Target: Active Region
xcen=139 ycen=-367
Instrument: SOTSP
HOP/JOP: 315
Description:
The flow and magnetic fields surrounding an active region (AR) filament play an important role in filament formation, their evolution and disruption. AR filament eruptions are often related to coronal mass ejections (CMEs) (e.g., Low et al. 2001, JGR 106, 25141
Gopalswamy et al. 2003, ApJ 286, 562). CMEs are the most energetic events in the solar system expelling up to 10 13 kg of coronal material from the Sun at speeds of several hundreds to thousands of kilometers per second. Since AR filaments and CMEs are closely connected and the primary cause of space weather disturbances, we need to understand their properties, especially their ultimate origin, precursors, and near-Sun evolution in order to predict them. Filaments are embedded in magnetic fields. Their plasma is sustained against gravity by magnetic field lines. There are several models which aim to explain this phenomenon. The sheared arcade models show sheared field lines below an unsheared coronal arcade (Antiochos et al. 1994, APJL 420, 41) where plasma can be stored. Eventually, reconnection can happen between the sheared and overlying unsheared field lines producing helical field lines (DeVore and Antiochos 2000, APJ 539, 954-963) which are typically called flux ropes. The well-know flux-rope model from van Ballegooijen and Martens (1989, APJ 343, 971-984) attempts to explain how these helical structures are formed in the chromosphere or corona when combining photospheric converging flows and shearing motions at the magnetic neutral line producing reconnection processes. So far, there are only few observations of active region filaments to support the aforementioned models (e.g., Okamoto et al. 2008, APJ 673, L215-L218
Lites et al. 2010, APJ 718, 474-487
Kuckein et al. 2012, AandA 539, A131
Kuckein et al. 2012, AandA 542, A112
Xu et al. 2012, APJ 749, 138). Furthermore, such a study requires simultaneous and coordinated observations of several layers of the Sun, including spectropolarimetry. Improved measurements of the photospheric and chromospheric three-dimensional magnetic and flow fields are crucial for a precise determination of the origin and evolution of AR filaments. We will carry out such measurements based on high-resolution vector magnetograms and three-dimensional flow field observations. Transverse flow field measurements will be based on speckle reconstructed intensity images. This provides a more realistic approximation of the real plasma velocity fields rather than velocity measurements derived from longitudinal magnetograms. Combining photospheric and chromospheric vector magnetograms (e.g., Yelles Chaouche et al. 2012, APJ 748, 23) will make it possible to understand how AR filaments are formed and how they eventually evolve towards a CME.
