Emergence of Twisted Flux in Prominence Observations

The emergence of twisted flux is a key process for the supply of magnetic flux into the corona as well as for solar dynamic activities such as sunspot formation and trigger of coronal mass ejections. In particular, there are numerous discussions about the role and necessity of twisted flux emergence for origin of prominences. However, the difficulty to measure vector magnetic fields has not allowed us to investigate the detailed relationship between emerging twisted flux and prominences. Hinode has changed this situation. The Spectro-Polarimeter aboard Hinode has high sensitivity to the weak magnetic fields of fine structures, and provides opportunities to detect weak horizontal fields. As a result, we have obtained signatures of twisted flux emergence associated with prominences: the observational features are "broadening and narrowing of a region dominated by horizontal magnetic field" and "rotating direction of horizontal field" in the photosphere. Moreover, the data show the interaction between the emerging twisted flux and granules, and that the flux rope has high intrinsic strength of 650 G, while the flux density is as low as 100 G. Theoretical research with numerical simulation on the basis of these results is active. In addition, we investigate activities of a coronal cavity overlying a prominence on the limb, and suggest the existence of a twisted flux rope to explain the activities of the prominence and the coronal cavity comprehensively. Here we introduce both these observational and theoretical results, and discuss details of emerging twisted flux.