Modeling ionospheric absorption modified by anomalous heating during substorms

Riometers monitor the changes in ionospheric conductivity by measuring the absorption of very high frequency radio noise of galactic origin passing th rough the ionosphere. In this Letter the absorption of radio signals by a t hin layer of ionospheric plasma, produced by ionization due to energetic pr ecipitating electrons, is modeled by taking into account strong turbulent h eating caused by instabilities. The precipitating electron population is ob tained from a global MHD simulation of the magnetosphere, along with the el ectric fields which excite the Farley-Buneman instability and lead to turbu lent electron heating. A comparison, the first of its kind, of the data fro m polar and sub-auroral riometers for the magnetic cloud event of January 1 0, 1997 shows good agreement. The ionospheric conductance modified by turbu lent electron heating can be used to improve the magnetosphere ionosphere c oupling in the current global MHD models.