Observational Evidence for Coronal Twisted Flux Rope

Abstract

Multi-instrument data sets of NOAA AR10938 on 2007 January 16 (e.g., Hinode, STEREO, GOES, MLSO, and ISOON Hα) are utilized to study the fine structure and evolution of a magnetic loop system exhibiting multiple crossing threads, whose arrangement and individual shapes are very suggestive of individual field lines in a flux rope. The footpoints of the magnetic threads are closely rooted into pores and plage areas. A C-class flare recorded by GOES at approximately 2:35 UT near one of the footpoints of the multi-thread system (along with a wisp of loop material shown by EUV data) led to the brightening of the magnetic structure revealing its fine structure with several threads that indicate a high degree of linking (suggesting a left-handed helical pattern as shown by the filament structure formed later on). EUV observations by Hinode/EIS of hot spectral lines at 2:46 UT show a complex structure of coronal loops. The same features were observed about 20 minutes later in X-ray images from Hinode/XRT and about 30 minutes further in EUV images of STEREO/SECCHI/EUVI with much better resolution. Hα and 304 Å images revealed the presence of several filament fibrils in the same area. They evolved a few hours later into a denser structure seemingly showing a helical pattern, which persisted or several days forming a segment of a larger-scale filament. The present observations provide an important indication for a flux robe as a precursor of a solar filament.