报告题目: Role of plasmoids in energy cascades in magnetic reconnection in solar flares: Modelling and relation to observations

　　报 告 人: Dr. Miroslav Barta （European ALMA Regional Centre - Czech node, Astronomical Institute of Academy of Sciences）

　　摘    要：Magnetic reconnection is nowadays a commonly accepted mechanism for energy dissipation in solar flares. Nevertheless, really efficient reconnection, in a such collision-less plasma as the solar flaring corona is, works at very small scales: The width of the dissipative current layer typically reaches ion skin depth or electron Larmor radius. Under solar conditions such scales are of the order of meters while the macroscopic flare current layers, believed to be formed behind the ejected filament/CME, are some six orders of magnitude thicker. Hence, some mechanism of cascading from large to small scales is required.

　Starting from 90's continuously more evidence is collected that formation and interaction of magnetic islands/plasmoids - which are helical magnetic flux ropes in the 3D reality - can provide such mechanism. There is a quite close analogy with the helical vortex tubes, whose formation and mutual interaction play this role in classical fluid dynamics.

　　Furthermore, namely recent observations demonstrate that formation and interaction of plasmoids is indeed involved in the real solar flares: Extension of MHD simulations providing simulated observations in optical, UV/EUV and radio domains and their comparison with the data really observed during the solar flares bring strong indication of the role of plasmoids in the solar flares.

　　The contribution aims at reviewing and summarizing recent development in the MHD and PIC simulations of plasmoid-dominated reconnection as well as related observations. At the end, emerging diagnostic possibilities - not only for the magnetic reconnection and flares, but in the broad range of solar research- related to the large millimeter interferometric array ALMA will be briefly introduced.

　　时    间：2014年10月28日星期二 上午10:30

　　地    点: 紫台办公大楼517会议室

　　联 系 人：封莉

　　电    话：83332177

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