30th URSI Convention on Radio Science, Sodankylä, Finland, 9-10 October 2006

Can ionospheric D-region opacity for cosmic radio waves be modulated by artificial HF heating?

A. Kero, C.-F. Enell, Th.Ulich, E. Turunen

Sodankylä Geophysical Observatory, Sodankylä, Finland


The effect of artificial D-region heating on cosmic radio noise absorption has been theoretically estimated but not yet quantitatively observed. In this study a 3-dimensional modelling of the effect produced by EISCAT Heater Facility and observed by the IRIS imaging riometer (Kilpisjärvi, Finland) is presented. In addition, a statistical analysis is done for data from the IRIS imaging riometer (Kilpisjärvi, Finland) corresponding to a selected set of EISCAT heating experiments carried out 1994-2004.

A small but statistically significant median offset signature is seen in IRIS beam number 9, which overlaps the EISCAT heater beam at D-region altitudes around 90 km. The found median absorption difference between heated and unheated ionosphere is approximately 0.003 dB, which is roughly one order of magnitude less than the model predicts.