  Gamma-ray bursts (GRBs) might be powered by a black hole (BH) hyperaccretion
systems via the Blandford-Znajek (BZ) mechanism or neutrino annihilation from
neutrino-dominated accretion flows (NDAFs). Magnetic coupling (MC) between the
inner disc and BH can transfer angular momentum and energy from the
fast-rotating BH to the disc. The neutrino luminosity and neutrino annihilation
luminosity are both efficiently enhanced by the MC process. In this paper, we
study the structure, luminosity, MeV neutrinos, and gravitational waves (GWs)
of magnetized NDAFs (MNDAFs) under the assumption that both the BZ and MC
mechanisms are present. The results indict that the BZ mechanism will compete
with the neutrino annihilation luminosity to trigger jets under the different
partitions of the two magnetic mechanisms. The typical neutrino luminosity and
annihilation luminosity of MNDAFs are definitely higher than those of NDAFs.
The typical peak energy of neutrino spectra of MNDAFs is higher than that of
NDAFs, but similar to those of core-collapse supernovae. Moreover, if the MC
process is dominant, then the GWs originating from the anisotropic neutrino
emission will be stronger particularly for discs with high accretion rates.
