Abstract
The first detailed comparison between gyrokinetic and gyrofluid simulations
of collisionless magnetic reconnection has been carried out. Both the linear
and nonlinear evolution of the collisionless tearing mode have been analyzed.
In the linear regime, we have found a good agreement between the two approaches
over the whole spectrum of linearly unstable wave numbers, both in the drift
kinetic limit and for finite ion temperature. Nonlinearly, focusing on the
small-\$\Delta '\$ regime, with \$\Delta '\$ indicating the standard tearing
stability parameter, we have compared relevant observables such as the
evolution and saturation of the island width, as well as the island oscillation
frequency in the saturated phase.The results are basically the same, with small
discrepancies only in the value of the saturated island width for moderately
high values of \$\Delta '\$. Therefore, in the regimes investigated here, the
gyrofluid approach can describe the collisionless reconnection process as well
as the more complete gyrokinetic model.
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