  Multiple scattering from artificial random irregularities HF-induced in the
ionosphere F region causes significant attenuation of both ordinary and
extraordinary radio waves together with the conventional anomalous absorption
of ordinary waves due to their conversion into the plasma waves. To study in
detail features of this effect, purposeful measurements of the attenuation of
weak probing waves of the extraordinary polarization have been performed at the
Sura heating facility. Characteristic scale lengths of the involved
irregularities are ~0.1-1 km across the geomagnetic field lines. To determine
the spectral characteristics of these irregularities from the extraordinary
probing wave attenuation measurements, a simple procedure of the inverse
problem solving has been implemented and some conclusions about the artificial
irregularity features have been drawn. Theory and details of experiments have
been stated earlier. This paper reports results of two experimental campaigns
carried out in August 2000 and June 2001 under support of Russian Foundation
for Basic Research (grants No. 99-02-17525 and No. 01-02-31008). Particularity
of these experiments consisted in using of lower heating power (20-80 MW ERP).
Regular character of the multiple scattering effects has been confirmed.
