  The electron-cyclotron maser emission from electron holes is applied to holes
generated in the downstream current region of the aurora. We suggest that part
of the fine structure observed in the auroral kilometric radiation is generated
by the electron-cyclotron maser mechanism in the downstream current region. The
argument goes that the main background auroral kilometric radiation source is
still located in the partial electron ring (horseshoe) distribution of the
upward current region while the fine structure is caused by electron holes
generated predominantly in the downward current region. Since both regions
always exist simultaneously they are acting in tandem in generating auroral
kilometric radiation by the same mechanism though in different ways.
