All-sky interferometric riometry

Abstract

The first implementation of a Fourier-based interferometric riometry technique for measuring electron density induced ionospheric opacity at VHF radio frequencies is presented. Unlike multibeam riometers, which form discrete beams on the sky, the interferometric technique permits all-sky sampling of incoming cosmic radio noise emissions resulting in a spatially continuous radiogram of the entire sky. The map of the received power at each time may then be compared to the equivalent map from a "quiet day," allowing the morphology of ionospheric absorption of cosmic radio noise to be ascertained. In this work, the high-latitude Kilpisjärvi Atmospheric Imaging Receiver Array was used to carry out the first interferometric riometry measurements in late 2013, producing all-sky absorption maps of space-weather-related ionization in the D region.