Homologous Flux Ropes Observed by SDO/AIA

We firstly present the Solar Dynamics Observatory observations of four homologous flux ropes in active region (AR) 11745 on 2013 May 20-22. The four flux ropes are all above the neutral line of the AR, with endpoints anchoring at the same region, and have the generally similar morphology. For the first three flux ropes, they rose up with a velocity of less than 30 km s$^{-1}$ after their appearances, and subsequently their intensities at 131 {\AA} decreased and the flux ropes became obscure. The fourth flux rope erupted ultimately with a speed of about 130 km s$^{-1}$ and formed a coronal mass ejection. The associated filament showed an obvious anti-clockwise twist motion at the initial stage, and the twist was estimated at 4$\pi$. This indicates that kink instability possibly triggers the early rise of the fourth flux rope. The activated filament material was spatially within the flux rope and they showed consistent evolution in their early stages. Our findings provide new clues for understanding the characteristics of flux ropes. Firstly, there are multiple flux ropes that are successively formed at the same location during an AR evolution process. Secondly, a slow-rise flux rope does not necessarily result in a CME, and a fast-eruption flux rope results in a CME.Comment: 15 pages, 5 figures, accepted in ApJ

Subarcsecond Bright Points and Quasi-periodic Upflows Below a Quiescent Filament Observed by the IRIS

Using UV spectra and SJIs from the IRIS, and coronal images and magnetograms from the Solar Dynamics Observatory (SDO), we present the new features in a quiescent filament channel: subarcsecond bright points (BPs) and quasi-periodic upflows. The BPs in the TR have a spatial scale of about 350$-$580 km and lifetime of more than several tens of minutes. They are located at stronger magnetic structures in the filament channel, with magnetic flux of about 10$^{17}$$-$10$^{18}$ Mx. Quasi-periodic brightenings and upflows are observed in the BPs and the period is about 4$-$5 min. The BP and the associated jet-like upflow comprise a "tadpole-shaped" structure. The upflows move along bright filament threads and their directions are almost parallel to the spine of the filament. The upflows initiated from the BPs with opposite polarity magnetic fields have opposite directions. The velocity of the upflows in plane of sky is about 5$-$50 km s$^{-1}$. The emission line of Si IV 1402.77 {\AA} at the locations of upflows exhibits obvious blueshifts of about 5$-$30 km s$^{-1}$, and the line profile is broadened with the width of more than 20 km s$^{-1}$. The BPs seem to be the bases of filament threads and the upflows are able to convey mass for the dynamic balance of the filament. The "counter-streaming" flows in previous observations may be caused by the propagation of bi-directional upflows initiated from opposite polarity magnetic fields. We suggest that quasi-periodic brightenings of BPs and quasi-periodic upflows result from small-scale oscillatory magnetic reconnections, which are modulated by solar p-mode waves.Comment: 6 pages, 6 figures, accepted in A&