Magnetic reconnection in three-dimensional quasi-helical pinches
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CLASSICAL AND QUANTUM PLASMAS
Magnetic reconnection in three‑dimensional quasi‑helical pinches Marco Veranda1 · Susanna Cappello1 · Daniele Bonfiglio1 · Dominique Franck Escande2 · Artur Kryzhanovskyy1 Received: 2 April 2020 / Accepted: 29 July 2020 © Accademia Nazionale dei Lincei 2020
Abstract This paper deals with the phenomenology of magnetic reconnection during reversed-field pinch helical self-organization. Numerical results obtained by solving a three-dimensional nonlinear visco-resistive fluid model to describe the hot currentcarrying plasma are summarized. Magnetic reconnection manifests itself during the plasma dynamics, interrupting the persistence of quasi-helical states. The main signatures of magnetic reconnection in reversed-field pinches are discussed: partial conversion of magnetic into kinetic energy, current sheet formation, steepening of plasma current profiles, locking of the angular phases between different Fourier components of the magnetic field. The latter is recognized as the threedimensional trigger of the reconnection events. Then the paper deals with the temporal scales of the process: low viscoresistive dissipation in the model, corresponding to high plasma current in the experiments, results in longer characteristic time between reconnection events. Furthermore, it is confirmed that the scaling of the reconnection rate is compatible with a modified Sweet–Parker model. A discussion of magnetic reconnection during the 2D simplified tokamak internal kink mode evolution, showing the development of secondary tearing instabilities, is presented and the similarities with RFP evolution are highlighted. Keywords Magnetic confinement of hot plasmas · Magnetic reconnection · Reversed-field pinch · Three-dimensional physics
1 Introduction Magnetic reconnection is a change of connections of magnetic field lines in highly conducting plasmas. A modification of the magnetic field topology results (Biskamp 1994; Yamada et al. 2010; Boozer 2012). Magnetic reconnection is a common phenomenon in space and laboratory plasmas: it is found in solar flares1 (Innes et al. 1997), planetary
This paper is a peer-reviewed version of a contribution at the International Conference “Plasma Physics and Astrophysics up to 2020 and beyond” organized by the Department of Physics of Università della Calabria in honor of Pierluigi Veltri’s 70th birthday and held October 7–8, 2019 at Università della Calabria, Rende (Italy) * Marco Veranda [email protected] 1
Consorzio RFX (CNR, ENEA, INFN, Università di Padova, Acciaierie Venete SpA) Corso Stati Uniti 4, Padova, Italy
Aix-Marseille Univ, CNRS, PIIM, UMR7345, Marseille, France
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magnetosphere, jets from active galactic nuclei (Romanova and Lovelace 1992), strongly magnetized neutron stars2 (Hurley et al. 2005), and laser-plasma interaction (Yi et al. 2018). Reconnection occurs also in astrophysical dynamos3 (Cowling 1934; Parker 1955), and in the large-scale magnetic self-organization of toroidal plasmas for magnetic fusion experiments (Taylor 1
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