We report flare ribbons approach (FRA) during a multiple-ribbon M-class flare on 2015 November 4 in NOAA AR 12443, obtained by the Interface Region Imaging Spectrograph and the Solar Dynamics Observatory. The flare consisted of a pair of main ribbons and two pairs of secondary ribbons. The two pairs of secondary ribbons were formed later than the appearance of main ribbons, with respective time delays of 15 and 19 minutes. The negative-polarity main ribbon spread outward faster than the first secondary ribbon with the same polarity in front of it, and thus the FRA was generated. Just before their encounter, the main ribbon was darkening drastically and its intensity decreased by about 70 % in 2 minutes, implying the suppression of main-phase reconnection that produced two main ribbons. The FRA caused the deflection of the main ribbon to the direction of secondary ribbon with a deflection angle of about 60• . Post-approach arcade was formed about 2 minutes later and the downflows were detected along the new arcade with velocities of 35−40 km s −1 , indicative of the magnetic restructuring during the process of FRA. We suggest that there are three topological domains with footpoints outlined by the three pairs of ribbons. Close proximity of these domains leads to deflection of the ribbons in agreement with the magnetic field topology.
Two Zhundong coals, Nanlutian coal and Wucaiwan coal, were pretreated by a sequential extraction; alkali and alkaline earth metals (AAEMs) in different occurrence modes were separated from the coal samples. The contents and compositions of AAEMs in coal were investigated, and then a kinetic model was used to quantify their catalytic behavior. Experimental results show that the content of water-soluble AAEMs is high and that these AAEMs are composed mainly of NaCl and other sodium species. After removing these AAEMs from the Nanlutian coal and the Wucaiwan coal, the activation energy required for gasification increases by 7.679 and 4.035 kJ mol −1 , respectively. Some of the sodium, potassium, calcium, and magnesium species exist in ion-exchangeable form, but the content is low. When the ion-exchangeable AAEMs were removed, the activation energy increases by 5.117 and 1.400 kJ mol −1 , respectively. The content of acid-soluble AAEMs is high and composed mainly of calcium and magnesium salts. After removing these AAEMs, the activation energy was increased by 2.002 and 0.537 kJ mol −1 , respectively.Finally, the content of insoluble AAEMs is very high, and this fraction is composed mainly of silicates and aluminosilicates. As these AAEMs are stable, their catalytic effect could be ignored.
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