  The vortex state thermal and transport properties of the high T_c copper
oxides can be understood in a d-wave gap model and are dominated by the
extended quasiparticle states that exist along the nodal directions in momentum
space. The Doppler shift on these states due to the circulating supercurrents
around the vortex core, introduces new van Hove ridges into the energy
dependent local density of states (LDOS) as a function of distance in the
region between cores. We emphasize the topology of these ridges and the effect
on them of local impurity scattering in Born and unitary limit. We treat
possible orthorhombicity. Effective local scttering rates are also obtaines.
