SURA-WIND experiments: wave scattering effects for Earth's magnetotail

Experiments on receiving of radio signals transmitted by the Russian SURA facility by the NASA WIND spacecraft in the frame of the Space Weather problem have been conducted since August 1995. Some results of recent SURA-WIND sessions at 9 MHz in November 2003 and February 2004 when the s/c was located in Earth's magnetotail at distances about 1.5 and 1 million km respectively are presented here. Ulike previous stages of the work, the transmission was carried out at two coherent frequencies f_1 and f_2 simultaneously, the signals were recorded by the s/c receiver using two adjacent channels with center frequencies of 50 kHz apart and HPBW bandwidth of 20 kHz in special dual fixed frequency mode. The aim was to study the correlation properties of the intensity fluctuations of the observed radio signals caused by the wave propagation effects at different sounding frequencies. Various df = f_1-f_2 mistuning over the interval from 30 up to 80 kHz were examinated. It was found that for the geophysical conditions (night time of winter season, s/c localization in magnetospheric tail) the frequency correlation radius ho is about 40-50 kHz, and the spectral width δf for each operating frequency is about 0.03 - 0.1 Hz. At the same time for individual session the mutual correlation coefficient depends not only on df, but also on spectral width, decreasing for larger δf. It was marked too that the ho(f) deminishs with increasing s/c distance. The observed behaviours are compared to modern concepts on wave scattering phenomena in random media to estimate the parameters of plasma inhomogeneties in Earth's magnetospheric tail. The possible applications of the obtained results to planned experiments on radio sounding of near space objects at decameter wavelenghts on basis of the SURA facility and Ukraine UTR-2 radio telescope are discussed too.