The electron-cyclotron maser emission theory from electron holes is applied to holes generated in the down- ward current region of the aurora. It is argued that the main background auroral kilometric radiation source may still be located in the upward current region electron-ring (horseshoe) distribution while the fine structure is caused by electron holes predominantly in the downward current re- gion. There the existence of electron holes is well established and electron densities are high enough for substantial maser growth rates. Trapping of radiation by the holes provides strong amplification. Upward motion of holes favours the escape of radiation both, from the holes and from the down- ward current region, into the upward current region. Since upward and downward current regions always exist simulta- neously, they are acting in tandem in generating auroral kilo- metric radiation and its fine structure by the same mechanism though in different ways. This mechanism solves the long- standing problem of auroral kilometric radiation fine struc- ture.
Treumann, R A.; Baumjohann, W; and Pottelette, R, "Electron-cylotron maser radiation from electron holes: downward current region" (2012). Open Dartmouth: Faculty Open Access Articles. 434.