Riometer (Relative Ionospheric Opacity Meter) has been used to measure ionospheric absorption of cosmic radio noise. In the auroral and polar cap regions, cosmic radio noise absorption (CNA) in the ionosphere is dominantly caused by precipitation of auroral particles from the magnetosphere into the ionosphere.
The Imaging Riometer for Ionospheric Studies (IRIS) was first developed at South Pole station, Antarctica (invariant latitude, -74°) (Detrick and Rosenberg, 1990). The IRIS data provides us characteristics of spatial-scale, form and motion of the absorption feature.
The IRIS at Ny Ålesund (NAL), Svalbard (invariant latitude, 76.1°N) was installed in September, 1991 by the research-group of the Ionospheric and Magnetospheric Environment in Solar-Terrestrial Environment Laboratory (STEL), Nagoya University, Japan. The IRIS observations are continuously carried out up to the present by the incessant support of Norwegian Polar Institute (NPI). We can store the IRIS data during about 12 years, and here would like to open ionospheric absorption data processed from the IRIS data.