%0 Journal Article %T On the origin of the plasma current spike during a tokamak disruption and its relation with magnetic stochasticity %+ Institut de Recherche sur la Fusion par confinement Magnétique (IRFM) %+ Max-Planck-Institut %+ ITER organization (ITER) %A Nardon, E. %A Särkimäki, K. %A Artola, F., J. %A Sadouni, S. %< avec comité de lecture %@ 0029-5515 %J Nuclear Fusion %I IOP Publishing %V 63 %N 5 %P 056011 %8 2023-03-30 %D 2023 %R 10.1088/1741-4326/acc417 %Z Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph]Journal articles %X A JOREK 3D non-linear MHD simulation of a disruption triggered by an argon massive gas injection in JET, which quantitatively reproduces the plasma current ($I_p$) spike, is analyzed in order to investigate the origin of the $I_p$ spike and its relation with magnetic stochasticity. The $I_p$ spike is associated to a current density ($j_ φ$) profile relaxation which appears to result from Shear Alfvén Wave (SAW) propagation along stochastic field lines, as proposed by Boozer, possibly complemented by a macroscopic E×B flow structure. Using axisymmetric JOREK simulations involving a mean field Ohm's law, we verify that the level of hyper-resistivity associated to SAWs is consistent with the prediction made in, which connects the $I_p$ spike with the level of stochasticity. The relaxation comprises two main phases, the first one corresponding to a fast (0.1 ms) and almost complete $j_φ$ flattening in the q < 2 region, while the second one is longer (0.5 ms) and corresponds to a more gradual, global and incomplete $j_φ$ flattening. During the first phase, strong E×B flows develop that play a key role in mixing impurities into the core. %G English %2 https://cea.hal.science/cea-04061073/document %2 https://cea.hal.science/cea-04061073/file/Nardon_Ip_spike_First_Revision_090123%20%28002%29.pdf %L cea-04061073 %U https://cea.hal.science/cea-04061073 %~ CEA %~ OPENAIRE %~ DSM-IRFM %~ CEA-DRF %~ CEA-CAD