The detection of a binary neutron star merger in 2017 through both
gravitational waves and electromagnetic emission opened a new era of
multimessenger astronomy. During the merger, several mechanisms like the
Kelvin-Helmholtz instability, the winding up effect and the MRI, can
amplify the initial magnetic field in the remnant to be powerful enoguh
for launching a jet, with an associated short GRB. When performing
simulations, simplified assumptions arise for the initial magnetic field
strength and topology of the merging neutron stars. Here I will show
convergent results by using high-resolution, large-eddy simulations of
binary neutron star mergers, following the newly formed remnant for up
to 30 milliseconds. I will specifically compare simulations with
different initial magnetic field strenghts and configurations, going
beyond the widespread-used aligned dipole confined within each star. I
will show that the magnetic field is always amplified up to ~10^16 G in
the bulk region of the remnant, while the initial topology is quickly
forgotten in a timescale of few miliseconds after the merger due to the
Kelvin-Helmholtz instability.