  Swift J164449+573451 is a peculiar outburst which is most likely powered by
the tidal disruption of a star by a massive black hole. Within the tidal
disruption scenario, we show that the periastron distance is considerably
smaller than the disruption radius and the outflow should be launched mainly
via magnetic activities (e.g., Blandford-Znajek process) otherwise the observed
long-lasting X-ray afterglow emission satisfying the relation
$L_{X}\propto\dot{M}$ can not be reproduced, where $L_{X}$ is the X-ray
luminosity and $\dot{M}$ is the accretion rate. We also suggest that
$L_{X}\propto\dot{M}$ may hold in the quick decline phase of Gamma-ray Bursts.
