We present a formation process of a filament in active region NOAA 12574 during the period from 2016 August 11 to 12. Combining the observations of GONG Hα, Hida spectrum and SDO/AIA 304 A, the formation process of the filament is studied. It is found that cool material (T ∼ 10 4 K) is ejected by a series of jets originating from the western foot-point of the filament. Simultaneously, the magnetic flux emerged from the photosphere in the vicinity of the western foot-point of the filament. These observations suggest that cool material in the low atmosphere can be directly injected into the upper atmosphere and the jets are triggered by the magnetic reconnection between pre-existing magnetic fields and new emerging magnetic fields. Detailed study of a jet at 18:02 UT on August 11 with GST/BBSO TiO observations reveals that some dark threads appeared in the vicinity of the western foot-point after the jet and the projection velocity of plasma along the filament axis was about 162.6±5.4 km/s. Using with DST/Hida observations, we find that the injected plasma by a jet at 00:42 UT on August 12 was rotating. Therefore, we conclude that the jets not only supplied the material for the filament, but also injected the helicity into the filament simultaneously. Comparing the quantity of mass injection by the jets with the mass of the filament, we conclude that the estimated mass loading by the jets is sufficient to account for the mass in the filament.

Using multi-wavelength data of Hinode, a rapid rotation of a sunspot in active region NOAA 10930 is studied in detail. We found the extra-ordinary counterclockwise rotation of the sunspot with positive polarity before an X3.4 flare. From a series of vector magnetograms, it is found that the magnetic force lines highly sheared along the neutral line accompanying the sunspot rotation. Furthermore, it is also found that the sheared loops and an inverse S-shaped magnetic loop in the corona formed gradually after the sunspot rotation.The X3.4 flare can be reasonably regarded as a result of this movement. The detailed analysis provides an evidence that sunspot rotation leads to magnetic field lines twisting in the photosphere, the twist is then transported into the corona, and finally flares are triggered.Abstract Using multi-wavelength data of Hinode, a rapid rotation of a sunspot in active region NOAA 10930 is studied in detail. We found the extra-ordinary counterclockwise rotation of the sunspot with positive polarity before an X3.4 flare. From a series of vector magnetograms, it is found that the magnetic force lines highly sheared along the neutral line accompanying the sunspot rotation. Furthermore, it is also found that the sheared loops and an inverse S-shaped magnetic loop in the corona formed gradually after the sunspot rotation.The X3.4 flare can be reasonably regarded as a result of this movement. The detailed analysis provides an evidence that sunspot rotation leads to magnetic field lines twisting in the photosphere, the twist is then transported into the corona, and finally flares are triggered.

Since the magnetic field is responsible for most manifestations of solar activity, one of the most challenging problems in solar physics is the diagnostics of solar magnetic fields, particularly in the outer atmosphere. To this end, it is important to develop rigorous diagnostic tools to interpret polarimetric observations in suitable spectral lines. This paper is devoted to analyzing the diagnostic content of linear polarization imaging observations in coronal forbidden lines. Although this technique is restricted to off-limb observations, it represents a significant tool to diagnose the magnetic field structure in the solar corona, where the magnetic field is intrinsically weak and still poorly known. We adopt the quantum theory of polarized line formation developed in the framework of the density matrix formalism, and synthesize images of the emergent linear polarization signal in coronal forbidden lines using potential-field source-surface magnetic field models. The influence of electronic collisions, active regions, and Thomson scattering on the linear polarization of coronal forbidden lines is also examined. It is found that active regions and Thomson scattering are capable of conspicuously influencing the orientation of the linear polarization. These effects have to be carefully taken into account to increase the accuracy of the field diagnostics. We also found that linear polarization observation in suitable lines can give valuable information on the long-term evolution of the magnetic field in the solar corona.