Latitudinal dynamics of auroral roar emissions

Auroral roar, a narrowband (delta f/f < 0.1) emission near 2 and 3 times th e ionospheric electron gyrofrequency (2f(ce) and 3f(ce)), is observed with a meridional chain of LF/MF/HF radio receivers located in northern Canada s panning 67 degrees to 79 degrees invariant latitude. Observations of these emissions are compared with the auroral electrojet location inferred from t he Canadian Auroral Network for the OPEN Program Unified Study (CANOPUS) ma gnetometer array. Variations in the intensity of the observed auroral roar emissions and in the invariant latitude of the most intense emissions are c orrelated with movements of the poleward boundary of the electrojet. For ex ample, substorm onsets, which appear as rapid poleward expansions of this b oundary, result in screening of the emissions from the underlying ground st ations because of precipitation-induced ionization in the lower ionosphere. In four of the five study days the peak emission intensity is located 0 de grees-9 degrees poleward of the poleward electrojet boundary inferred from the magnetometers. In one case the peak emission intensity is up to 10 degr ees equatorward of the poleward electrojet boundary. In all cases, there is a tendency for the latitude of the most intense auroral roar emissions to track the movements of the electrojet location inferred from the magnetomet er data. For two examples, the footprint of the Fast Auroral Snapshot (FAST ) satellite passes within 3 degrees of one or more of the ground stations, and the satellite detects unstable electron populations in the polewardmost auroral are, reinforcing the scenario that auroral roar emissions are gene rated by these electrons in the polewardmost are and propagate into the pol ar cap where conditions are often favorable for their detection at ground l evel.