High Time Resolution Riometer And X-Ray Measurements Of Conjugate Electron-Precipitation From The Magnetosphere

In this letter we describe the comparison of cosmic noise absorption data recorded by a riometer at Siple Station, Antarctica (76 °S; 84 °W; L ∼4.2) with simultaneous balloon measurements of bremsstrahlung X rays from the conjugate region near Roberval, Canada (48.3° N; 72.1° W). Both the cosmic noise absorption and the production of X rays are caused by the precipitation of energetic electrons (E ≳ 15 ke V) from the magnetosphere. The time resolution and spatial coverage of the measurements enable us for the first time to show the similarity and simultaneity of rapid fluctuations of electron precipitation at ionospheric conjugate points. Furthermore, the data suggest that fast-response riometers are capable of resolving temporal structures in electron precipitation on a time scale which approaches that of electron microbursts (of the order of 1 s). The relative simplicity of riometers for the measurement of precipitating particle effects opens up important new avenues of research in studies of upper atmosphere ionisation phenoma.