  The electron current density in nanoscale junctions is typically several
orders of magnitude larger than the corresponding one in bulk electrodes.
Consequently, the electron-electron scattering rate increases substantially in
the junction. This leads to local electron heating of the underlying Fermi sea
in analogy to the local ionic heating that is due to the increased
electron-phonon scattering rates. We predict the bias dependence of local
electron heating in quasi-ballistic nanoscale conductors, its effect on ionic
heating, and discuss possible experimental tests of our results.
