  Low magnetic field scanning tunneling spectroscopy of individual Abrikosov
vortices in heavily overdoped Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ unveils a
clear d-wave electronic structure of the vortex core, with a zero-bias
conductance peak at the vortex center that splits with increasing distance from
the core. We show that previously reported unconventional electronic
structures, including the low energy checkerboard charge order in the vortex
halo and the absence of a zero-bias conductance peak at the vortex center, are
direct consequences of short inter-vortex distance and consequent vortex-vortex
interactions prevailing in earlier experiments.
