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Merging of magnetic islands as an efficient accelerator of electrons

Research output: Contribution to journalJournal article

Published

Article number102902
Journal publication date7/10/2010
JournalPhysics of Plasmas
Journal number10
Volume17
Number of pages11
Original languageEnglish

Abstract

In a thin elongated current sheet, it is likely that more than one X-line forms and thus multiple magnetic islands are produced. The islands are then subject to merging. By simulating such a case with a two-dimensional full-particle code, we show that a merger forming a large island produces the most energetic electron population in the system. By setting the lateral extent of the simulation box to be as large as ∼ 100 ion inertial lengths, we introduce many (16) small islands in the initial thin current sheet ( ∼ 1 ion inertial length thickness). Merging of these islands proceeds to leave only two islands in the system. Then, strong electron acceleration is seen upon the final merger that produces the single island in the large simulation box. The most energetic electrons in the system are accelerated at the merging line. The merging line acceleration dominates because the reverse-reconnection facilitating the final merger is in such a strongly driven manner that the associated electric field is an order of magnitude larger than those available upon normal reconnection. Combining the results from additional runs enables us to obtain a scaling law, which suggests a non-negligible role played by merging lines in the observed electron acceleration phenomena.

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