Coronal mass ejections (CMEs) are the most spectacular eruptive phenomena inthe solar atmosphere. It is generally accepted that CMEs are results oferuptions of magnetic flux ropes (MFRs). However, a heated debate is on whetherMFRs pre-exist before the eruptions or they are formed during the eruptions.Several coronal signatures, \textit{e.g.}, filaments, coronal cavities, sigmoidstructures and hot channels (or hot blobs), are proposed as MFRs and observedbefore the eruption, which support the pre-existing MFR scenario. There isalmost no reported observation about MFR formation during the eruption. In thisletter, we present an intriguing observation of a solar eruptive event occurredon 2013 November 21 with the Atmospheric Imaging Assembly on board the\textit{Solar Dynamic Observatory}, which shows a detailed formation process ofthe MFR during the eruption. The process started with the expansion of alow-lying coronal arcade, possibly caused by the flare magnetic reconnectionunderneath. The newly-formed ascending loops from below further pushed thearcade upward, stretching the surrounding magnetic field. The arcade andstretched magnetic field lines then curved-in just below the arcade vertex,forming an X-point. The field lines near the X-point continued to approach eachother and a second magnetic reconnection was induced. It is this high-lyingmagnetic reconnection that led to the formation and eruption of a hot blob($\sim$ 10 MK), presumably a MFR, producing a CME. We suggest that twospatially-separated magnetic reconnections occurred in this event, responsiblefor producing the flare and the hot blob (CME), respectively.
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